diff --git a/playground/add_sub_mul_div.html b/playground/add_sub_mul_div.html
index 07fb093c..9f43f48c 100644
--- a/playground/add_sub_mul_div.html
+++ b/playground/add_sub_mul_div.html
@@ -192,7 +192,7 @@ <h2>2 — add: Series + Series (positional)</h2>
 
 const a = new Series({ data: [1, 2, 3] });
 const b = new Series({ data: [4, 5, 6] });
-seriesAdd(a, b).values;  // [5, 7, 9]</textarea>
+console.log(seriesAdd(a, b).values);  // [5, 7, 9]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -213,8 +213,8 @@ <h2>3 — sub / rsub</h2>
       <textarea class="playground-editor" spellcheck="false">import { Series, seriesSub, seriesRsub } from "tsb";
 
 const s = new Series({ data: [10, 20, 30] });
-seriesSub(s, 5).values;    // [5, 15, 25]
-seriesRsub(s, 100).values; // [90, 80, 70]</textarea>
+console.log(seriesSub(s, 5).values);    // [5, 15, 25]
+console.log(seriesRsub(s, 100).values); // [90, 80, 70]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -235,10 +235,10 @@ <h2>4 — mul: multiply</h2>
       <textarea class="playground-editor" spellcheck="false">import { Series, seriesMul } from "tsb";
 
 const s = new Series({ data: [1, 2, 3, null] });
-seriesMul(s, 3).values;  // [3, 6, 9, null]
+console.log(seriesMul(s, 3).values);  // [3, 6, 9, null]
 
 const weights = new Series({ data: [0.5, 1, 2, 1] });
-seriesMul(s, weights).values;  // [0.5, 2, 6, null]</textarea>
+console.log(seriesMul(s, weights).values);  // [0.5, 2, 6, null]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -261,8 +261,8 @@ <h2>5 — div / rdiv (true division)</h2>
       <textarea class="playground-editor" spellcheck="false">import { Series, seriesDiv, seriesRdiv } from "tsb";
 
 const s = new Series({ data: [4, 9, 0, null] });
-seriesDiv(s, 2).values;    // [2, 4.5, Infinity, null]
-seriesRdiv(s, 36).values;  // [9, 4, Infinity, null]</textarea>
+console.log(seriesDiv(s, 2).values);    // [2, 4.5, Infinity, null]
+console.log(seriesRdiv(s, 36).values);  // [9, 4, Infinity, null]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -285,13 +285,13 @@ <h2>6 — DataFrame arithmetic</h2>
 const df = DataFrame.fromColumns({ price: [10, 20, 30], qty: [3, 5, 2] });
 
 // Add a discount
-dataFrameAdd(df, 5).col("price").values;   // [15, 25, 35]
+console.log(dataFrameAdd(df, 5).col("price").values);   // [15, 25, 35]
 
 // Scale everything by 2
-dataFrameMul(df, 2).col("qty").values;     // [6, 10, 4]
+console.log(dataFrameMul(df, 2).col("qty").values);     // [6, 10, 4]
 
 // Revenue per item / some constant
-dataFrameDiv(df, 10).col("price").values;  // [1, 2, 3]</textarea>
+console.log(dataFrameDiv(df, 10).col("price").values);  // [1, 2, 3]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -312,9 +312,9 @@ <h2>7 — Missing value propagation</h2>
       <textarea class="playground-editor" spellcheck="false">import { Series, seriesAdd, seriesMul, seriesDiv } from "tsb";
 
 const s = new Series({ data: [1, null, NaN, 4] });
-seriesAdd(s, 10).values;  // [11, null, NaN, 14]
-seriesMul(s, 2).values;   // [2, null, NaN, 8]
-seriesDiv(s, 2).values;   // [0.5, null, NaN, 2]</textarea>
+console.log(seriesAdd(s, 10).values);  // [11, null, NaN, 14]
+console.log(seriesMul(s, 2).values);   // [2, null, NaN, 8]
+console.log(seriesDiv(s, 2).values);   // [0.5, null, NaN, 2]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/align.html b/playground/align.html
index aa8da364..2699b1e7 100644
--- a/playground/align.html
+++ b/playground/align.html
@@ -168,8 +168,8 @@ <h2>1 · alignSeries — outer (default)</h2>
 
 // Default join="outer" → union of indices
 const [la, ra] = alignSeries(a, b);
-la.toArray();  // → [1, 2, 3]     (index: a, b, c)
-ra.toArray();  // → [null, 10, 20] (index: a, b, c)</textarea>
+console.log(la.toArray());  // → [1, 2, 3]     (index: a, b, c)
+console.log(ra.toArray());  // → [null, 10, 20] (index: a, b, c)</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -186,8 +186,8 @@ <h2>2 · alignSeries — inner join</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">const [li, ri] = alignSeries(a, b, { join: "inner" });
-li.toArray();  // → [2, 3]   (only shared labels: b, c)
-ri.toArray();  // → [10, 20]</textarea>
+console.log(li.toArray());  // → [2, 3]   (only shared labels: b, c)
+console.log(ri.toArray());  // → [10, 20]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -208,13 +208,13 @@ <h2>3 · alignSeries — left / right join + fillValue</h2>
 
 // join="left": result index = x's index
 const [ll, rl] = alignSeries(x, y, { join: "left", fillValue: 0 });
-ll.toArray();  // → [1, 2, 3]
-rl.toArray();  // → [0, 10, 0]  ("d" is outside x's index → dropped)
+console.log(ll.toArray());  // → [1, 2, 3]
+console.log(rl.toArray());  // → [0, 10, 0]  ("d" is outside x's index → dropped)
 
 // join="right": result index = y's index
 const [lr, rr] = alignSeries(x, y, { join: "right", fillValue: 0 });
-lr.toArray();  // → [2, 0]      ("b" matches, "d" is new)
-rr.toArray();  // → [10, 30]</textarea>
+console.log(lr.toArray());  // → [2, 0]      ("b" matches, "d" is new)
+console.log(rr.toArray());  // → [10, 30]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -247,13 +247,13 @@ <h2>4 · alignDataFrame — outer, both axes</h2>
 // la  →  shape [2, 3]  columns: x, y, z
 //        row r0: x=1, y=3, z=null
 //        row r1: x=2, y=4, z=null
-la.col("z").toArray();  // → [null, null]
+console.log(la.col("z").toArray());  // → [null, null]
 
 // ra  →  shape [2, 3]  columns: x, y, z
 //        row r0: x=null, y=null, z=null
 //        row r1: x=null, y=10,   z=20
-ra.col("x").toArray();  // → [null, null]
-ra.col("y").toArray();  // → [null, 10]</textarea>
+console.log(ra.col("x").toArray());  // → [null, null]
+console.log(ra.col("y").toArray());  // → [null, 10]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -271,10 +271,10 @@ <h2>5 · alignDataFrame — axis=0 (rows only)</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">// axis=0 aligns rows but leaves columns untouched
 const [la5, ra5] = alignDataFrame(a, b, { axis: 0 });
-la5.columns.toArray();  // → ["x", "y"]   (unchanged)
-ra5.columns.toArray();  // → ["y", "z"]   (unchanged)
-la5.index.toArray();    // → ["r0", "r1"] (outer union)
-ra5.index.toArray();    // → ["r0", "r1"] (outer union)</textarea>
+console.log(la5.columns.toArray());  // → ["x", "y"]   (unchanged)
+console.log(ra5.columns.toArray());  // → ["y", "z"]   (unchanged)
+console.log(la5.index.toArray());    // → ["r0", "r1"] (outer union)
+console.log(ra5.index.toArray());    // → ["r0", "r1"] (outer union)</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -292,10 +292,10 @@ <h2>6 · alignDataFrame — axis=1 (columns only)</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">// axis=1 aligns columns but leaves rows untouched
 const [la6, ra6] = alignDataFrame(a, b, { axis: 1 });
-la6.index.toArray();    // → ["r0", "r1"]  (unchanged)
-ra6.index.toArray();    // → ["r1"]        (unchanged)
-la6.columns.toArray().sort();  // → ["x", "y", "z"]
-ra6.columns.toArray().sort();  // → ["x", "y", "z"]</textarea>
+console.log(la6.index.toArray());    // → ["r0", "r1"]  (unchanged)
+console.log(ra6.index.toArray());    // → ["r1"]        (unchanged)
+console.log(la6.columns.toArray().sort());  // → ["x", "y", "z"]
+console.log(ra6.columns.toArray().sort());  // → ["x", "y", "z"]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -318,8 +318,8 @@ <h2>7 · Arithmetic after alignment</h2>
 const [ap, aq] = alignSeries(p, q, { fillValue: 0 });
 // Now same shape — do element-wise addition
 const sum = ap.add(aq);
-sum.toArray();   // → [100, 201, 302]
-sum.index.toArray();  // → ["a", "b", "c"]</textarea>
+console.log(sum.toArray());   // → [100, 201, 302]
+console.log(sum.index.toArray());  // → ["a", "b", "c"]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/api_types.html b/playground/api_types.html
index c91b3478..8a12cbd7 100644
--- a/playground/api_types.html
+++ b/playground/api_types.html
@@ -167,12 +167,12 @@ <h2>isScalar(val)</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">import { isScalar } from "tsb";
 
-isScalar(42);            // true
-isScalar("hello");       // true
-isScalar(null);          // true
-isScalar(new Date());    // true
-isScalar([1, 2]);        // false
-isScalar({ a: 1 });      // false</textarea>
+console.log(isScalar(42));            // true
+console.log(isScalar("hello"));       // true
+console.log(isScalar(null));          // true
+console.log(isScalar(new Date()));    // true
+console.log(isScalar([1, 2]));        // false
+console.log(isScalar({ a: 1 }));      // false</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -189,10 +189,10 @@ <h2>isListLike(val)</h2>
           <button class="playground-reset">↺ Reset</button>
         </div>
       </div>
-      <textarea class="playground-editor" spellcheck="false">isListLike([1, 2, 3]);      // true
-isListLike(new Set([1]));   // true
-isListLike("abc");          // false
-isListLike(42);             // false</textarea>
+      <textarea class="playground-editor" spellcheck="false">console.log(isListLike([1, 2, 3]));      // true
+console.log(isListLike(new Set([1])));   // true
+console.log(isListLike("abc"));          // false
+console.log(isListLike(42));             // false</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -209,9 +209,9 @@ <h2>isArrayLike(val)</h2>
           <button class="playground-reset">↺ Reset</button>
         </div>
       </div>
-      <textarea class="playground-editor" spellcheck="false">isArrayLike([1, 2]);      // true
-isArrayLike("hello");     // true
-isArrayLike(42);          // false</textarea>
+      <textarea class="playground-editor" spellcheck="false">console.log(isArrayLike([1, 2]));      // true
+console.log(isArrayLike("hello"));     // true
+console.log(isArrayLike(42));          // false</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -228,9 +228,9 @@ <h2>isDictLike(val)</h2>
           <button class="playground-reset">↺ Reset</button>
         </div>
       </div>
-      <textarea class="playground-editor" spellcheck="false">isDictLike({ a: 1 });   // true
-isDictLike(new Map());  // true
-isDictLike([]);         // false</textarea>
+      <textarea class="playground-editor" spellcheck="false">console.log(isDictLike({ a: 1 }));   // true
+console.log(isDictLike(new Map()));  // true
+console.log(isDictLike([]));         // false</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -246,14 +246,14 @@ <h2>isNumber / isBool / isStringValue / isFloat / isInteger</h2>
           <button class="playground-reset">↺ Reset</button>
         </div>
       </div>
-      <textarea class="playground-editor" spellcheck="false">isNumber(3.14);      // true
-isNumber(NaN);       // true  (typeof NaN === "number")
-isBool(true);        // true
-isStringValue("hi"); // true
-isFloat(3.14);       // true
-isFloat(3.0);        // false  (integer value)
-isInteger(42);       // true
-isInteger(3.14);     // false</textarea>
+      <textarea class="playground-editor" spellcheck="false">console.log(isNumber(3.14));      // true
+console.log(isNumber(NaN));       // true  (typeof NaN === "number")
+console.log(isBool(true));        // true
+console.log(isStringValue("hi")); // true
+console.log(isFloat(3.14));       // true
+console.log(isFloat(3.0));        // false  (integer value)
+console.log(isInteger(42));       // true
+console.log(isInteger(3.14));     // false</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -270,10 +270,10 @@ <h2>isMissing(val)</h2>
           <button class="playground-reset">↺ Reset</button>
         </div>
       </div>
-      <textarea class="playground-editor" spellcheck="false">isMissing(null);       // true
-isMissing(undefined);  // true
-isMissing(NaN);        // true
-isMissing(0);          // false</textarea>
+      <textarea class="playground-editor" spellcheck="false">console.log(isMissing(null));       // true
+console.log(isMissing(undefined));  // true
+console.log(isMissing(NaN));        // true
+console.log(isMissing(0));          // false</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -290,9 +290,9 @@ <h2>isHashable(val)</h2>
           <button class="playground-reset">↺ Reset</button>
         </div>
       </div>
-      <textarea class="playground-editor" spellcheck="false">isHashable("key");  // true
-isHashable(42);     // true
-isHashable({});     // false</textarea>
+      <textarea class="playground-editor" spellcheck="false">console.log(isHashable("key"));  // true
+console.log(isHashable(42));     // true
+console.log(isHashable({}));     // false</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -312,20 +312,20 @@ <h2>Dtype-Level Predicates</h2>
       <textarea class="playground-editor" spellcheck="false">import { Dtype, isNumericDtype, isFloatDtype, isIntegerDtype,
          isStringDtype, isDatetimeDtype, isCategoricalDtype } from "tsb";
 
-isNumericDtype(Dtype.float64);    // true
-isNumericDtype("int32");          // true
-isNumericDtype("string");         // false
+console.log(isNumericDtype(Dtype.float64));    // true
+console.log(isNumericDtype("int32"));          // true
+console.log(isNumericDtype("string"));         // false
 
-isFloatDtype("float32");          // true
-isIntegerDtype("int64");          // true
-isUnsignedIntegerDtype("uint8");  // true
-isSignedIntegerDtype("int8");     // true
-isStringDtype("string");          // true
-isDatetimeDtype("datetime");      // true
-isCategoricalDtype("category");   // true
-isObjectDtype("object");          // true
-isExtensionArrayDtype("category"); // true
-isExtensionArrayDtype("int32");    // false</textarea>
+console.log(isFloatDtype("float32"));          // true
+console.log(isIntegerDtype("int64"));          // true
+console.log(isUnsignedIntegerDtype("uint8"));  // true
+console.log(isSignedIntegerDtype("int8"));     // true
+console.log(isStringDtype("string"));          // true
+console.log(isDatetimeDtype("datetime"));      // true
+console.log(isCategoricalDtype("category"));   // true
+console.log(isObjectDtype("object"));          // true
+console.log(isExtensionArrayDtype("category")); // true
+console.log(isExtensionArrayDtype("int32"));    // false</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/assign.html b/playground/assign.html
index 9cdf746e..99327e6b 100644
--- a/playground/assign.html
+++ b/playground/assign.html
@@ -172,7 +172,8 @@ <h2>Example 1 — Array and Series</h2>
 
 // df2.columns.values  →  ["a", "b", "c", "d"]
 // df2.col("c").values →  [7, 8, 9]
-// df2.col("d").values →  [4, 5, 6]</textarea>
+// df2.col("d").values →  [4, 5, 6]
+console.log(df2);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -198,7 +199,8 @@ <h2>Example 2 — Callable (chained derivations)</h2>
 });
 
 // df3.col("total").values  →  [11, 22, 33]
-// df3.col("tax").values    →  [1.1, 2.2, 3.3]</textarea>
+// df3.col("tax").values    →  [1.1, 2.2, 3.3]
+console.log(df3);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -218,7 +220,8 @@ <h2>Example 3 — Instance method</h2>
 const df4 = df.assign({
   squared_a: (d: DataFrame) =&gt; d.col("a").values.map((v) =&gt; (v as number) ** 2),
 });
-// df4.col("squared_a").values  →  [1, 4, 9]</textarea>
+// df4.col("squared_a").values  →  [1, 4, 9]
+console.log(df4);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -238,7 +241,8 @@ <h2>Example 4 — Replace an existing column</h2>
 const df5 = dataFrameAssign(df, { b: [100, 200, 300] });
 
 // df5.columns.values   →  ["a", "b"]  (order unchanged)
-// df5.col("b").values  →  [100, 200, 300]</textarea>
+// df5.col("b").values  →  [100, 200, 300]
+console.log(df5);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/at_iat.html b/playground/at_iat.html
index 5d4d782b..d7029e21 100644
--- a/playground/at_iat.html
+++ b/playground/at_iat.html
@@ -186,8 +186,8 @@ <h2>seriesAt — access by label</h2>
       <textarea class="playground-editor" spellcheck="false">import { Series, seriesAt } from "tsb";
 
 const s = new Series({ data: [10, 20, 30], index: ["a", "b", "c"] });
-seriesAt(s, "b");   // 20
-seriesAt(s, "a");   // 10</textarea>
+console.log(seriesAt(s, "b"));   // 20
+console.log(seriesAt(s, "a"));   // 10</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -224,8 +224,8 @@ <h2>seriesIat — access by integer position</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">import { seriesIat } from "tsb";
 
-seriesIat(s, 2);   // 30
-seriesIat(s, -1);  // 30</textarea>
+console.log(seriesIat(s, 2));   // 30
+console.log(seriesIat(s, -1));  // 30</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -266,8 +266,8 @@ <h2>dataFrameAt — access by row label and column name</h2>
   { x: [1, 2], y: [3, 4] },
   { index: ["r0", "r1"] },
 );
-dataFrameAt(df, "r1", "x");   // 2
-dataFrameAt(df, "r0", "y");   // 3</textarea>
+console.log(dataFrameAt(df, "r1", "x"));   // 2
+console.log(dataFrameAt(df, "r0", "y"));   // 3</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -304,8 +304,8 @@ <h2>dataFrameIat — access by integer row and column position</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">import { dataFrameIat } from "tsb";
 
-dataFrameIat(df, 0, 1);   // 3  (row 0, column index 1 = "y")
-dataFrameIat(df, 1, -1);  // 4  (last column, row 1)</textarea>
+console.log(dataFrameIat(df, 0, 1));   // 3  (row 0, column index 1 = "y")
+console.log(dataFrameIat(df, 1, -1));  // 4  (last column, row 1)</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/attrs.html b/playground/attrs.html
index 9e747813..52aab333 100644
--- a/playground/attrs.html
+++ b/playground/attrs.html
@@ -180,14 +180,14 @@ <h2>Basic usage</h2>
   notes: "Morning readings",
 });
 
-getAttrs(df);
+console.log(getAttrs(df));
 // → { source: "weather_station_42", unit: "Celsius", notes: "Morning readings" }
 
-getAttr(df, "unit");     // → "Celsius"
-getAttr(df, "missing");  // → undefined
-attrsCount(df);          // → 3
-attrsKeys(df);           // → ["source", "unit", "notes"]
-hasAttrs(df);            // → true</textarea>
+console.log(getAttr(df, "unit"));     // → "Celsius"
+console.log(getAttr(df, "missing"));  // → undefined
+console.log(attrsCount(df));          // → 3
+console.log(attrsKeys(df));           // → ["source", "unit", "notes"]
+console.log(hasAttrs(df));            // → true</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -204,14 +204,14 @@ <h2>Merging and updating</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">// updateAttrs merges new keys, preserves existing
-updateAttrs(df, { version: 2, notes: "Updated notes" });
-getAttrs(df);
+console.log(updateAttrs(df, { version: 2, notes: "Updated notes" }));
+console.log(getAttrs(df));
 // → { source: "weather_station_42", unit: "Celsius", notes: "Updated notes", version: 2 }
 
 // setAttr / deleteAttr for single keys
-setAttr(df, "sensor_id", "WS-042");
-deleteAttr(df, "notes");
-getAttrs(df);
+console.log(setAttr(df, "sensor_id", "WS-042"));
+console.log(deleteAttr(df, "notes"));
+console.log(getAttrs(df));
 // → { source: "weather_station_42", unit: "Celsius", version: 2, sensor_id: "WS-042" }</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -230,17 +230,17 @@ <h2>Propagating metadata to derived objects</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">// copyAttrs: copy all attrs from one object to another
 const s = new Series({ data: [22.1, 23.5, 21.8], name: "temperature" });
-setAttrs(s, { unit: "Celsius", source: "sensor_A" });
+console.log(setAttrs(s, { unit: "Celsius", source: "sensor_A" }));
 
 const derived = new Series({ data: [71.8, 74.3, 71.2], name: "fahrenheit" });
-copyAttrs(s, derived);
-getAttrs(derived);
+console.log(copyAttrs(s, derived));
+console.log(getAttrs(derived));
 // → { unit: "Celsius", source: "sensor_A" }
 
 // Then update the copy
-setAttr(derived, "unit", "Fahrenheit");
-getAttrs(derived);  // → { unit: "Fahrenheit", source: "sensor_A" }
-getAttrs(s);        // → { unit: "Celsius", source: "sensor_A" }  ← unchanged</textarea>
+console.log(setAttr(derived, "unit", "Fahrenheit"));
+console.log(getAttrs(derived));  // → { unit: "Fahrenheit", source: "sensor_A" }
+console.log(getAttrs(s));        // → { unit: "Celsius", source: "sensor_A" }  ← unchanged</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -264,7 +264,7 @@ <h2>Fluent helper — withAttrs</h2>
 );
 
 annotated === annotated;  // true — same reference, not a copy
-getAttrs(annotated);
+console.log(getAttrs(annotated));
 // → { source: "lab_experiment", date: "2026-04-09" }</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -284,13 +284,13 @@ <h2>Merging from multiple sources</h2>
       <textarea class="playground-editor" spellcheck="false">// mergeAttrs: combine attrs from multiple objects into a target
 const s1 = new Series({ data: [1, 2, 3], name: "a" });
 const s2 = new Series({ data: [4, 5, 6], name: "b" });
-setAttrs(s1, { source: "sensor_A", unit: "kg" });
-setAttrs(s2, { source: "sensor_B", scale: 2.5 });
+console.log(setAttrs(s1, { source: "sensor_A", unit: "kg" }));
+console.log(setAttrs(s2, { source: "sensor_B", scale: 2.5 }));
 
 const combined = DataFrame.fromColumns({ a: [1, 2, 3], b: [4, 5, 6] });
-mergeAttrs([s1, s2], combined);
+console.log(mergeAttrs([s1, s2], combined));
 // Later sources win on conflicts: source="sensor_B"
-getAttrs(combined);
+console.log(getAttrs(combined));
 // → { source: "sensor_B", unit: "kg", scale: 2.5 }</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -307,13 +307,13 @@ <h2>Clearing metadata</h2>
           <button class="playground-reset">↺ Reset</button>
         </div>
       </div>
-      <textarea class="playground-editor" spellcheck="false">setAttrs(df, { x: 1, y: 2 });
-hasAttrs(df);   // → true
-attrsCount(df); // → 2
+      <textarea class="playground-editor" spellcheck="false">console.log(setAttrs(df, { x: 1, y: 2 }));
+console.log(hasAttrs(df));   // → true
+console.log(attrsCount(df)); // → 2
 
-clearAttrs(df);
-hasAttrs(df);   // → false
-getAttrs(df);   // → {}</textarea>
+console.log(clearAttrs(df));
+console.log(hasAttrs(df));   // → false
+console.log(getAttrs(df));   // → {}</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/between.html b/playground/between.html
index 42d725c0..eec2cda7 100644
--- a/playground/between.html
+++ b/playground/between.html
@@ -192,7 +192,7 @@ <h2>seriesBetween — inclusive="both" (default)</h2>
       <textarea class="playground-editor" spellcheck="false">import { Series, seriesBetween } from "tsb";
 
 const s = new Series({ data: [1, 2, 3, 4, 5] });
-seriesBetween(s, 2, 4).values;
+console.log(seriesBetween(s, 2, 4).values);
 // [false, true, true, true, false]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -242,13 +242,13 @@ <h2>Inclusive options</h2>
 
 const s = new Series({ data: [1, 2, 3, 4, 5] });
 
-seriesBetween(s, 2, 4, { inclusive: "left" }).values;
+console.log(seriesBetween(s, 2, 4, { inclusive: "left" }).values);
 // [false, true, true, false, false]
 
-seriesBetween(s, 2, 4, { inclusive: "right" }).values;
+console.log(seriesBetween(s, 2, 4, { inclusive: "right" }).values);
 // [false, false, true, true, false]
 
-seriesBetween(s, 2, 4, { inclusive: "neither" }).values;
+console.log(seriesBetween(s, 2, 4, { inclusive: "neither" }).values);
 // [false, false, true, false, false]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -291,7 +291,7 @@ <h2>Missing values</h2>
       <textarea class="playground-editor" spellcheck="false">import { Series, seriesBetween } from "tsb";
 
 const s = new Series({ data: [1, null, NaN, 4] });
-seriesBetween(s, 0, 5).values;
+console.log(seriesBetween(s, 0, 5).values);
 // [true, false, false, true]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -333,7 +333,7 @@ <h2>String comparison</h2>
       <textarea class="playground-editor" spellcheck="false">import { Series, seriesBetween } from "tsb";
 
 const s = new Series({ data: ["apple", "banana", "cherry", "date"] });
-seriesBetween(s, "banana", "cherry").values;
+console.log(seriesBetween(s, "banana", "cherry").values);
 // [false, true, true, false]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
diff --git a/playground/clip_advanced.html b/playground/clip_advanced.html
index a4f5ac8d..8798874a 100644
--- a/playground/clip_advanced.html
+++ b/playground/clip_advanced.html
@@ -194,7 +194,7 @@ <h2>Demo 1 — clipAdvancedSeries with scalar bounds</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">const s = new Series({ data: [-3, 1, 5, 10] });
-clipAdvancedSeries(s, { lower: 0, upper: 6 }).values;
+console.log(clipAdvancedSeries(s, { lower: 0, upper: 6 }).values);
 // → [0, 1, 5, 6]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -214,7 +214,7 @@ <h2>Demo 2 — clipAdvancedSeries with per-element array bounds</h2>
       <textarea class="playground-editor" spellcheck="false">const s = new Series({ data: [-1, 0, 5, 12] });
 const lo = [2, -1, 4, 10];
 const hi = [5,  3, 8, 11];
-clipAdvancedSeries(s, { lower: lo, upper: hi }).values;
+console.log(clipAdvancedSeries(s, { lower: lo, upper: hi }).values);
 // → [2, 0, 5, 11]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -234,7 +234,7 @@ <h2>Demo 3 — clipAdvancedSeries with Series bounds</h2>
       <textarea class="playground-editor" spellcheck="false">const s = new Series({ data: [0, 5, 10, 15] });
 const loBound = new Series({ data: [1, 3, 8, 12] });
 const hiBound = new Series({ data: [2, 7, 9, 20] });
-clipAdvancedSeries(s, { lower: loBound, upper: hiBound }).values;
+console.log(clipAdvancedSeries(s, { lower: loBound, upper: hiBound }).values);
 // → [1, 5, 9, 15]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -255,8 +255,8 @@ <h2>Demo 4 — clipAdvancedDataFrame with DataFrame bounds</h2>
 const lo = DataFrame.fromColumns({ a: [2, 3, 4], b: [1, 4, 8] });
 const hi = DataFrame.fromColumns({ a: [3, 7, 8], b: [5, 9, 12] });
 const result = clipAdvancedDataFrame(df, { lower: lo, upper: hi });
-result.col("a").values; // → [2, 5, 8]
-result.col("b").values; // → [2, 6, 10]</textarea>
+console.log(result.col("a").values); // → [2, 5, 8]
+console.log(result.col("b").values); // → [2, 6, 10]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -276,8 +276,8 @@ <h2>Demo 5 — clipAdvancedDataFrame with Series broadcast (axis=1)</h2>
 const df = DataFrame.fromColumns({ a: [1, 5, 9], b: [2, 6, 10] });
 const loPerRow = new Series({ data: [0, 4, 10] });
 const result = clipAdvancedDataFrame(df, { lower: loPerRow, axis: 1 });
-result.col("a").values; // → [1, 5, 10]
-result.col("b").values; // → [2, 6, 10]</textarea>
+console.log(result.col("a").values); // → [1, 5, 10]
+console.log(result.col("b").values); // → [2, 6, 10]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/clip_with_bounds.html b/playground/clip_with_bounds.html
index 27bfd394..f3df881e 100644
--- a/playground/clip_with_bounds.html
+++ b/playground/clip_with_bounds.html
@@ -165,7 +165,7 @@ <h2>Example 1 — Series with scalar bounds</h2>
 
 const s = new Series({ data: [-5, 1, 7, 12] });
 
-clipSeriesWithBounds(s, { lower: 0, upper: 8 }).values;
+console.log(clipSeriesWithBounds(s, { lower: 0, upper: 8 }).values);
 // [0, 1, 7, 8]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -196,7 +196,7 @@ <h2>Example 2 — Series bounds (label-aligned)</h2>
   index: new Index(["AAPL", "MSFT", "GOOG"]),
 });
 
-clipSeriesWithBounds(prices, { lower: floors }).values;
+console.log(clipSeriesWithBounds(prices, { lower: floors }).values);
 // AAPL: max(90, 95)=95  GOOG: max(110, 100)=110  MSFT: max(85, 80)=85  AMZN: 120 (no bound)
 // [95, 110, 85, 120]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
@@ -227,7 +227,8 @@ <h2>Example 3 — DataFrame clip with per-column bounds (axis=1)</h2>
 
 const result = clipDataFrameWithBounds(df, { lower: lo, upper: hi, axis: 1 });
 // col "a": [1, 5, 10]  (lower=1, upper=10)
-// col "b": [4, 8,  9]  (lower=4, upper=9)</textarea>
+// col "b": [4, 8,  9]  (lower=4, upper=9)
+console.log(result);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -255,7 +256,8 @@ <h2>Example 4 — DataFrame clip with per-row bounds (axis=0, default)</h2>
 const upperBound = new Series({ data: [12, 12, 20, 20] }); // row-specific caps
 
 const result = clipDataFrameWithBounds(df, { lower: lowerBound, upper: upperBound, axis: 0 });
-// min_temp: [0, 0, 1, 4]   max_temp: [10, 12, 18, 20]</textarea>
+// min_temp: [0, 0, 1, 4]   max_temp: [10, 12, 18, 20]
+console.log(result);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -278,7 +280,8 @@ <h2>Example 5 — Element-wise DataFrame bounds</h2>
 const hi = DataFrame.fromColumns({ a: [8, 8, 8], b: [5, 5, 5] });
 
 const result = clipDataFrameWithBounds(df, { lower: lo, upper: hi });
-// col "a": [3, 5, 8]  col "b": [2, 5, 3]</textarea>
+// col "a": [3, 5, 8]  col "b": [2, 5, 3]
+console.log(result);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -297,7 +300,7 @@ <h2>Null / NaN propagation</h2>
       <textarea class="playground-editor" spellcheck="false">import { Series, clipSeriesWithBounds } from "tsb";
 
 const s = new Series({ data: [null, -5, NaN, 10] });
-clipSeriesWithBounds(s, { lower: 0, upper: 8 }).values;
+console.log(clipSeriesWithBounds(s, { lower: 0, upper: 8 }).values);
 // [null, 0, NaN, 8]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
diff --git a/playground/combine.html b/playground/combine.html
index 617a8e08..b3114782 100644
--- a/playground/combine.html
+++ b/playground/combine.html
@@ -172,12 +172,12 @@ <h2>Code Examples</h2>
 const b = new Series({ data: [10, 2, 30], index: [0, 1, 2] });
 
 // Element-wise max
-combineSeries(a, b, (x, y) =&gt; Math.max(x, y)).values; // [10, 5, 30]
+console.log(combineSeries(a, b, (x, y) =&gt; Math.max(x, y)).values); // [10, 5, 30]
 
 // Union index with fillValue=0
 const c = new Series({ data: [1, 2], index: ["x", "y"] });
 const d = new Series({ data: [10, 30], index: ["x", "z"] });
-combineSeries(c, d, (x, y) =&gt; (x ?? 0) + (y ?? 0), 0).values;
+console.log(combineSeries(c, d, (x, y) =&gt; (x ?? 0) + (y ?? 0), 0).values);
 // x:11, y:2, z:30
 
 // ── DataFrame ───────────────────────────────────────────────────────────────
@@ -185,7 +185,7 @@ <h2>Code Examples</h2>
 const df2 = DataFrame.fromColumns({ a: [10, 2], c: [1000, 2000] });
 
 // Shared column "a": element-wise min; unshared columns processed with fillValue
-combineDataFrame(df1, df2, (p, q) =&gt; Math.min(p ?? Infinity, q ?? Infinity));
+console.log(combineDataFrame(df1, df2, (p, q) =&gt; Math.min(p ?? Infinity, q ?? Infinity)));
 
 // overwrite: false — unshared columns preserved as-is
 combineDataFrame(df1, df2, (p, q) =&gt; Math.min(p ?? Infinity, q ?? Infinity),
diff --git a/playground/combine_first.html b/playground/combine_first.html
index 0c664c8d..5ba8f393 100644
--- a/playground/combine_first.html
+++ b/playground/combine_first.html
@@ -173,7 +173,8 @@ <h2>Example 1 — Series: fill gaps with values from another Series</h2>
 // - "x": a has 1 (non-null) → keeps 1
 // - "y": a has null → filled from b → 20
 // - "z": a has 3 (non-null) → keeps 3
-// - "w": a has no entry → comes from b → 40</textarea>
+// - "w": a has no entry → comes from b → 40
+console.log(result);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -212,7 +213,8 @@ <h2>Example 2 — DataFrame: patch missing cells across row/column union</h2>
 // result["r2"]["y"] = null (no r2 in a, no y in b)
 // result["r0"]["z"] = 30  (b only)
 // result["r1"]["z"] = null (b has no r1)
-// result["r2"]["z"] = 40  (b only)</textarea>
+// result["r2"]["z"] = 40  (b only)
+console.log(result);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -243,7 +245,8 @@ <h2>Example 3 — NaN is treated as missing</h2>
 
 const merged = combineFirstSeries(sensor1, sensor2);
 // values: [21.0, 22.5, 23.1, 24.0]
-// Gaps in sensor1 filled from sensor2</textarea>
+// Gaps in sensor1 filled from sensor2
+console.log(merged);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -275,7 +278,8 @@ <h2>Example 4 — Temporal data backfill</h2>
 
 const complete = combineFirstSeries(primary, backup);
 // index:  2024-01, 2024-02, 2024-03, 2024-04, 2024-05, 2024-06
-// values: 100,     101,     102,     103,     104,     106</textarea>
+// values: 100,     101,     102,     103,     104,     106
+console.log(complete);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/compare.html b/playground/compare.html
index 7978f62d..dfd3fc32 100644
--- a/playground/compare.html
+++ b/playground/compare.html
@@ -170,7 +170,8 @@ <h2>1 — seriesEq with a scalar</h2>
 // → [false, true, false, true, false]
 
 // Use this as a boolean mask for filtering:
-// s.values.filter((_, i) =&gt; result.values[i]) → [2, 2]</textarea>
+// s.values.filter((_, i) =&gt; result.values[i]) → [2, 2]
+console.log(result);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -191,7 +192,7 @@ <h2>2 — seriesNe: inequality</h2>
 
 const s = new Series({ data: ["apple", "banana", "apple", "cherry"] });
 
-seriesNe(s, "apple").values;
+console.log(seriesNe(s, "apple").values);
 // → [false, true, false, true]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -213,8 +214,8 @@ <h2>3 — Ordering comparisons: lt, gt, le, ge</h2>
 
 const scores = new Series({ data: [45, 72, 88, 60, 95] });
 
-seriesLt(scores, 60).values;  // [true, false, false, false, false]
-seriesGe(scores, 60).values;  // [false, true, true, true, true]
+console.log(seriesLt(scores, 60).values);  // [true, false, false, false, false]
+console.log(seriesGe(scores, 60).values);  // [false, true, true, true, true]
 
 // lt and ge are always complementary for finite, non-null values:
 // lt[i] !== ge[i]  for every i</textarea>
@@ -239,8 +240,8 @@ <h2>4 — Comparing two Series element-by-element</h2>
 const actual   = new Series({ data: [1, 2, 3, 4] });
 const expected = new Series({ data: [1, 3, 3, 2] });
 
-seriesEq(actual, expected).values;  // [true, false, true, false]
-seriesLt(actual, expected).values;  // [false, true, false, false]
+console.log(seriesEq(actual, expected).values);  // [true, false, true, false]
+console.log(seriesLt(actual, expected).values);  // [false, true, false, false]
 
 // Throws RangeError if lengths differ</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
@@ -264,12 +265,12 @@ <h2>5 — Missing value behaviour</h2>
 
 const s = new Series({ data: [1, null, NaN, 3] });
 
-seriesEq(s, 1).values;    // [true,  false, false, false]
-seriesNe(s, 1).values;    // [false, false, false, true ]
-seriesLt(s, 2).values;    // [true,  false, false, false]
+console.log(seriesEq(s, 1).values);    // [true,  false, false, false]
+console.log(seriesNe(s, 1).values);    // [false, false, false, true ]
+console.log(seriesLt(s, 2).values);    // [true,  false, false, false]
 
 // null eq null → false (NaN != NaN convention)
-seriesEq(s, null).values;  // [false, false, false, false]</textarea>
+console.log(seriesEq(s, null).values);  // [false, false, false, false]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -293,10 +294,10 @@ <h2>6 — DataFrame comparison with a scalar</h2>
   science: [60, 45, 91],
 });
 
-dataFrameGt(df, 60).col("math").values;
+console.log(dataFrameGt(df, 60).col("math").values);
 // → [false, true, true]
 
-dataFrameLe(df, 60).col("science").values;
+console.log(dataFrameLe(df, 60).col("science").values);
 // → [true, true, false]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -319,8 +320,8 @@ <h2>7 — DataFrame compared against another DataFrame</h2>
 const df1 = DataFrame.fromColumns({ a: [1, 2], b: [3, 4] });
 const df2 = DataFrame.fromColumns({ a: [1, 0], b: [3, 5] });
 
-dataFrameEq(df1, df2).col("a").values;  // [true, false]
-dataFrameEq(df1, df2).col("b").values;  // [true, false]</textarea>
+console.log(dataFrameEq(df1, df2).col("a").values);  // [true, false]
+console.log(dataFrameEq(df1, df2).col("b").values);  // [true, false]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -345,7 +346,7 @@ <h2>8 — Combining with whereSeries for conditional selection</h2>
 const isWarm = seriesGe(temps, 20);  // [false, true, true, false, true]
 const warmOnly = whereSeries(temps, isWarm);
 
-warmOnly.values;  // [null, 22, 30, null, 27]</textarea>
+console.log(warmOnly.values);  // [null, 22, 30, null, 27]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/corrwith.html b/playground/corrwith.html
index eb19c248..507460d4 100644
--- a/playground/corrwith.html
+++ b/playground/corrwith.html
@@ -197,15 +197,15 @@ <h2>autoCorr — lag-N autocorrelation</h2>
       <textarea class="playground-editor" spellcheck="false">import { Series, autoCorr } from "tsb";
 
 const s = new Series({ data: [1, 2, 3, 4, 5] });
-autoCorr(s);          // lag=1 → 1.0
-autoCorr(s, 0);       // lag=0 → 1.0  (always)
-autoCorr(s, 2);       // lag=2 → 1.0
+console.log(autoCorr(s));          // lag=1 → 1.0
+console.log(autoCorr(s, 0));       // lag=0 → 1.0  (always)
+console.log(autoCorr(s, 2));       // lag=2 → 1.0
 
 const alt = new Series({ data: [1, -1, 1, -1, 1, -1] });
-autoCorr(alt, 1);     // -1.0
+console.log(autoCorr(alt, 1));     // -1.0
 
 const flat = new Series({ data: [5, 5, 5, 5] });
-autoCorr(flat, 1);    // NaN</textarea>
+console.log(autoCorr(flat, 1));    // NaN</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -258,7 +258,8 @@ <h2>corrWith — DataFrame correlated with a Series</h2>
 const s = new Series({ data: [1, 2, 3, 4, 5] });
 
 const result = corrWith(df, s);
-// Series(A=1.0, B=-1.0) indexed by column names</textarea>
+// Series(A=1.0, B=-1.0) indexed by column names
+console.log(result);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -316,11 +317,11 @@ <h2>corrWith — DataFrame correlated with another DataFrame</h2>
 const df1 = DataFrame.fromColumns({ A: [1, 2, 3], B: [4, 5, 6] });
 const df2 = DataFrame.fromColumns({ A: [1, 2, 3], B: [6, 5, 4] });
 
-corrWith(df1, df2);                         // A=1.0, B=-1.0
+console.log(corrWith(df1, df2));                         // A=1.0, B=-1.0
 
 const df3 = DataFrame.fromColumns({ A: [1, 2, 3], C: [7, 8, 9] });
-corrWith(df1, df3);                         // A=1.0, B=NaN, C=NaN
-corrWith(df1, df3, { drop: true });         // A=1.0</textarea>
+console.log(corrWith(df1, df3));                         // A=1.0, B=NaN, C=NaN
+console.log(corrWith(df1, df3, { drop: true }));         // A=1.0</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -371,7 +372,7 @@ <h2>corrWith — axis=1 (row-wise correlation)</h2>
 const df = DataFrame.fromColumns({ A: [1, 2], B: [2, 4], C: [3, 6] });
 const s = new Series({ data: [1, 2, 3] });
 
-corrWith(df, s, { axis: 1 });
+console.log(corrWith(df, s, { axis: 1 }));
 // Series([1.0, 1.0]) indexed by row labels [0, 1]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
diff --git a/playground/cut_bins_to_frame.html b/playground/cut_bins_to_frame.html
index 4a89d55e..2f7e3a46 100644
--- a/playground/cut_bins_to_frame.html
+++ b/playground/cut_bins_to_frame.html
@@ -177,7 +177,8 @@ <h2>What it does</h2>
 // { "(0.0, 25.0]": 5, "(25.0, 50.0]": 6, ... }
 
 // Just edges indexed by label
-const edges = binEdges(result);</textarea>
+const edges = binEdges(result);
+console.log(edges);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/cut_qcut.html b/playground/cut_qcut.html
index a3ac8533..b500e7e3 100644
--- a/playground/cut_qcut.html
+++ b/playground/cut_qcut.html
@@ -173,7 +173,8 @@ <h2>Integer bins</h2>
 // labels: ["(5.0, 26.7]", "(26.7, 48.3]", "(48.3, 70.0]"]
 // bins:   [4.935, 26.667, 48.333, 70]
 // codes:  [0, 0, 0, 1, 1, 2]
-console.table(ages.map((a, i) =&gt; ({ age: a, bin: labels[codes[i]!] })));</textarea>
+console.table(ages.map((a, i) =&gt; ({ age: a, bin: labels[codes[i]!] })));
+console.log(ages);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -196,7 +197,8 @@ <h2>Explicit bin edges</h2>
 });
 // codes:  [0, 1, 2, 3, 4, 4]
 // labels[codes[0]] → "F"
-// labels[codes[5]] → "A"</textarea>
+// labels[codes[5]] → "A"
+console.log(scores);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -218,7 +220,8 @@ <h2>Quartile split</h2>
 const { codes, labels, bins } = qcut(values, 4);
 
 // labels: ["[1, 3.25]", "(3.25, 5.5]", "(5.5, 7.75]", "(7.75, 10]"]
-// Every bin has ~2-3 elements</textarea>
+// Every bin has ~2-3 elements
+console.log(values);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/date-offset.html b/playground/date-offset.html
index a779f47e..5136589b 100644
--- a/playground/date-offset.html
+++ b/playground/date-offset.html
@@ -173,7 +173,8 @@ <h2>2 — Fixed-time offsets (Day, Hour, Minute, Second, Milli)</h2>
 new Hour(2).apply(d).toISOString();         // "2024-01-01T02:00:00.000Z"
 new Minute(90).apply(d).toISOString();      // "2024-01-01T01:30:00.000Z"
 new Second(30).apply(d).toISOString();      // "2024-01-01T00:00:30.000Z"
-new Milli(500).apply(d).getTime() - d.getTime();  // 500</textarea>
+new Milli(500).apply(d).getTime() - d.getTime();  // 500
+console.log(d);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -202,16 +203,16 @@ <h2>3 — Week offset</h2>
 
 // Weekday-aligned (weekday=0 → Monday)
 const wk = new Week(1, { weekday: 0 });
-wk.apply(wed).toISOString().slice(0, 10);    // "2024-01-22" (next Mon)
-wk.apply(mon).toISOString().slice(0, 10);    // "2024-01-22" (Mon → next Mon)
+console.log(wk.apply(wed).toISOString().slice(0, 10));    // "2024-01-22" (next Mon)
+console.log(wk.apply(mon).toISOString().slice(0, 10));    // "2024-01-22" (Mon → next Mon)
 
 // Rollforward / rollback
-wk.rollforward(wed).toISOString().slice(0, 10);  // "2024-01-22"
-wk.rollback(wed).toISOString().slice(0, 10);     // "2024-01-15"
+console.log(wk.rollforward(wed).toISOString().slice(0, 10));  // "2024-01-22"
+console.log(wk.rollback(wed).toISOString().slice(0, 10));     // "2024-01-15"
 
 // onOffset
-wk.onOffset(mon);   // true
-wk.onOffset(wed);   // false</textarea>
+console.log(wk.onOffset(mon));   // true
+console.log(wk.onOffset(wed));   // false</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -248,7 +249,8 @@ <h2>4 — MonthEnd &amp; MonthBegin</h2>
 new MonthBegin(-1).apply(mid).toISOString().slice(0, 10); // "2024-01-01"
 
 new MonthBegin(0).rollforward(mid).toISOString().slice(0, 10); // "2024-02-01"
-new MonthBegin(0).rollback(mid).toISOString().slice(0, 10);    // "2024-01-01"</textarea>
+new MonthBegin(0).rollback(mid).toISOString().slice(0, 10);    // "2024-01-01"
+console.log(end);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -279,7 +281,8 @@ <h2>5 — YearEnd &amp; YearBegin</h2>
 
 const yr2024 = new Date(Date.UTC(2024, 11, 31));
 new YearEnd(0).rollforward(yr2024).toISOString().slice(0, 10);  // "2024-12-31"
-new YearEnd(0).rollback(d).toISOString().slice(0, 10);          // "2023-12-31"</textarea>
+new YearEnd(0).rollback(d).toISOString().slice(0, 10);          // "2023-12-31"
+console.log(yr2024);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -316,7 +319,8 @@ <h2>6 — BusinessDay</h2>
 new BusinessDay(0).rollback(sat).toISOString().slice(0, 10);    // "2024-01-12"
 
 new BusinessDay(0).onOffset(fri);   // true
-new BusinessDay(0).onOffset(sat);   // false</textarea>
+new BusinessDay(0).onOffset(sat);   // false
+console.log(sat);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -344,7 +348,7 @@ <h2>7 — multiply &amp; negate</h2>
 const bday = new BusinessDay(3);
 const fri = new Date(Date.UTC(2024, 0, 12));
 
-bday.negate().apply(bday.apply(fri)).toISOString().slice(0, 10); // "2024-01-12"</textarea>
+console.log(bday.negate().apply(bday.apply(fri)).toISOString().slice(0, 10)); // "2024-01-12"</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -365,10 +369,10 @@ <h2>8 — Static factory methods</h2>
 
 const d = new Date(Date.UTC(2024, 0, 15));
 
-Day.of(5).apply(d).toISOString().slice(0, 10);          // "2024-01-20"
-MonthEnd.of(1).apply(d).toISOString().slice(0, 10);     // "2024-01-31"
-Week.of(1, { weekday: 0 }).apply(d).toISOString().slice(0, 10); // "2024-01-22"
-BusinessDay.of(2).apply(d).toISOString().slice(0, 10);  // "2024-01-17"</textarea>
+console.log(Day.of(5).apply(d).toISOString().slice(0, 10));          // "2024-01-20"
+console.log(MonthEnd.of(1).apply(d).toISOString().slice(0, 10));     // "2024-01-31"
+console.log(Week.of(1, { weekday: 0 }).apply(d).toISOString().slice(0, 10)); // "2024-01-22"
+console.log(BusinessDay.of(2).apply(d).toISOString().slice(0, 10));  // "2024-01-17"</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/dot_matmul.html b/playground/dot_matmul.html
index 9f53494f..fa74a324 100644
--- a/playground/dot_matmul.html
+++ b/playground/dot_matmul.html
@@ -167,16 +167,16 @@ <h2>API</h2>
 import { seriesDotSeries, seriesDotDataFrame, dataFrameDotSeries, dataFrameDotDataFrame } from "tsb";
 
 // Series · Series → scalar
-seriesDotSeries(a, b);
+console.log(seriesDotSeries(a, b));
 
 // Series · DataFrame → Series
-seriesDotDataFrame(s, df);
+console.log(seriesDotDataFrame(s, df));
 
 // DataFrame · Series → Series
-dataFrameDotSeries(df, s);
+console.log(dataFrameDotSeries(df, s));
 
 // DataFrame · DataFrame → DataFrame
-dataFrameDotDataFrame(A, B);</textarea>
+console.log(dataFrameDotDataFrame(A, B));</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -196,17 +196,17 @@ <h2>Examples</h2>
 // Series dot product
 const a = new Series({ data: [1, 2, 3], index: ["x","y","z"] });
 const b = new Series({ data: [4, 5, 6], index: ["x","y","z"] });
-seriesDotSeries(a, b); // 1*4 + 2*5 + 3*6 = 32
+console.log(seriesDotSeries(a, b)); // 1*4 + 2*5 + 3*6 = 32
 
 // DataFrame · vector
 const df = DataFrame.fromColumns({ a: [1, 2], b: [3, 4] });
 const v  = new Series({ data: [1, 1], index: ["a", "b"] });
-dataFrameDotSeries(df, v).values; // [4, 6]  (row sums)
+console.log(dataFrameDotSeries(df, v).values); // [4, 6]  (row sums)
 
 // Matrix multiply
 const A = DataFrame.fromColumns({ k: [1, 2] });     // 2×1
 // ... B with row index ["k"] ...
-dataFrameDotDataFrame(A, B).col("r").values;         // [3, 6]</textarea>
+console.log(dataFrameDotDataFrame(A, B).col("r").values);         // [3, 6]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/dropna.html b/playground/dropna.html
index 73aa6480..b8d57d92 100644
--- a/playground/dropna.html
+++ b/playground/dropna.html
@@ -166,8 +166,8 @@ <h2>Example 1 — Series: drop missing elements</h2>
 const s = new Series({ data: [1, null, NaN, 4, undefined, 6] });
 const clean = dropna(s);
 
-clean.values;  // [1, 4, 6]
-clean.size;    // 3</textarea>
+console.log(clean.values);  // [1, 4, 6]
+console.log(clean.size);    // 3</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -193,7 +193,7 @@ <h2>Example 2 — DataFrame: drop rows with any missing value (default)</h2>
 
 // Drop any row that has at least one null
 const clean = dropna(df);
-clean.shape;   // [1, 3]  — only "Alice" row survives (score=95, grade="A")</textarea>
+console.log(clean.shape);   // [1, 3]  — only "Alice" row survives (score=95, grade="A")</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -219,7 +219,7 @@ <h2>Example 3 — how = "all": only drop fully-null rows</h2>
 // Row 1: both null → dropped
 // Row 0 and Row 2: at least one non-null → kept
 const clean = dropna(df, { how: "all" });
-clean.shape;   // [2, 2]</textarea>
+console.log(clean.shape);   // [2, 2]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -248,7 +248,7 @@ <h2>Example 4 — thresh: require at least N non-null values</h2>
 // Row 1: 0 present → drop
 // Row 2: 2 present → keep
 const clean = dropna(df, { thresh: 2 });
-clean.shape;   // [2, 3]</textarea>
+console.log(clean.shape);   // [2, 3]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -275,7 +275,7 @@ <h2>Example 5 — subset: only check specific columns</h2>
 // Only check the "score" column for nulls — ignore "notes"
 const clean = dropna(df, { subset: ["score"] });
 // Row 1 (score=null) is dropped; Row 2 (notes=null but score=88) is kept.
-clean.shape;   // [2, 3]</textarea>
+console.log(clean.shape);   // [2, 3]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -300,8 +300,8 @@ <h2>Example 6 — axis = 1: drop columns with missing values</h2>
 });
 
 const clean = dropna(df, { axis: 1 });
-clean.columns.toArray();  // ["b"]
-clean.shape;              // [3, 1]</textarea>
+console.log(clean.columns.toArray());  // ["b"]
+console.log(clean.shape);              // [3, 1]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -326,7 +326,7 @@ <h2>Example 7 — axis = 1, how = "all": only drop all-null columns</h2>
 });
 
 const clean = dropna(df, { axis: 1, how: "all" });
-clean.columns.toArray();  // ["b", "c"]</textarea>
+console.log(clean.columns.toArray());  // ["b", "c"]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/duplicated.html b/playground/duplicated.html
index 21b3fffd..0f03a116 100644
--- a/playground/duplicated.html
+++ b/playground/duplicated.html
@@ -170,7 +170,7 @@ <h2>Example 1 — Basic: find duplicate rows</h2>
 
 // Row 2 ("Alice", 90) is a duplicate of Row 0
 const mask = duplicatedDataFrame(df);
-mask.values; // [false, false, true, false]</textarea>
+console.log(mask.values); // [false, false, true, false]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -194,7 +194,7 @@ <h2>Example 2 — Drop duplicate rows</h2>
 });
 
 const deduped = dropDuplicatesDataFrame(df);
-deduped.shape; // [3, 2]  — "Alice" row 2 removed</textarea>
+console.log(deduped.shape); // [3, 2]  — "Alice" row 2 removed</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -219,7 +219,7 @@ <h2>Example 3 — subset: only check specific columns</h2>
 
 // Drop based on "id" only — row 2 (id=1) is dup even though value differs
 const deduped = dropDuplicatesDataFrame(df, { subset: ["id"] });
-deduped.shape; // [3, 2]</textarea>
+console.log(deduped.shape); // [3, 2]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -242,11 +242,11 @@ <h2>Example 4 — keep="last": keep the last occurrence</h2>
 });
 
 // keep="last" → mark the FIRST occurrence of each dup, keep the last
-duplicatedDataFrame(df, { keep: "last" }).values;
+console.log(duplicatedDataFrame(df, { keep: "last" }).values);
 // [true, false, false, false]
 
 // keep=false → mark ALL occurrences of any duplicate
-duplicatedDataFrame(df, { keep: false }).values;
+console.log(duplicatedDataFrame(df, { keep: false }).values);
 // [true, false, true, false]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -267,11 +267,11 @@ <h2>Example 5 — Series: deduplicate values</h2>
 
 const s = new Series({ data: [1, 2, 1, 3, 2, 4] });
 
-duplicatedSeries(s).values;     // [false, false, true, false, true, false]
-dropDuplicatesSeries(s).values; // [1, 2, 3, 4]
+console.log(duplicatedSeries(s).values);     // [false, false, true, false, true, false]
+console.log(dropDuplicatesSeries(s).values); // [1, 2, 3, 4]
 
 // keep=false → mark all duplicate values
-duplicatedSeries(s, { keep: false }).values;
+console.log(duplicatedSeries(s, { keep: false }).values);
 // [true, true, true, false, true, false]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
diff --git a/playground/eval_query.html b/playground/eval_query.html
index 9e2bdedb..f0e5d47a 100644
--- a/playground/eval_query.html
+++ b/playground/eval_query.html
@@ -186,26 +186,26 @@ <h2>queryDataFrame(df, expr)</h2>
 });
 
 // Simple comparison
-queryDataFrame(df, "age &gt; 28");
+console.log(queryDataFrame(df, "age &gt; 28"));
 // name: ["Bob", "Dave"]  age: [32, 45]  score: [72, 60]
 
 // Combined conditions
-queryDataFrame(df, "age &lt; 35 and score &gt;= 85");
+console.log(queryDataFrame(df, "age &lt; 35 and score &gt;= 85"));
 // name: ["Alice", "Carol"]
 
 // String equality
-queryDataFrame(df, "name == 'Alice'");
+console.log(queryDataFrame(df, "name == 'Alice'"));
 // single row
 
 // 'in' operator
-queryDataFrame(df, "name in ['Alice', 'Carol']");
+console.log(queryDataFrame(df, "name in ['Alice', 'Carol']"));
 
 // 'not in' operator
-queryDataFrame(df, "age not in [25, 45]");
+console.log(queryDataFrame(df, "age not in [25, 45]"));
 
 // Backtick-quoted column (for names with spaces)
 const df2 = DataFrame.fromArrays({ "first name": ["Alice", "Bob"] });
-queryDataFrame(df2, "`first name` == 'Alice'");</textarea>
+console.log(queryDataFrame(df2, "`first name` == 'Alice'"));</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -228,20 +228,20 @@ <h2>evalDataFrame(df, expr)</h2>
 });
 
 // Arithmetic expression → new Series
-evalDataFrame(sales, "price * qty");
+console.log(evalDataFrame(sales, "price * qty"));
 // Series [1000, 1250, 1000, 400]
 
 // Boolean expression (useful as a mask)
-evalDataFrame(sales, "price &gt; 10");
+console.log(evalDataFrame(sales, "price &gt; 10"));
 // Series [false, true, false, true]
 
 // Function calls
-evalDataFrame(sales, "round(price * qty / 100, 1)");
+console.log(evalDataFrame(sales, "round(price * qty / 100, 1)"));
 // Series [10.0, 12.5, 10.0, 4.0]
 
 // String operations
 const df3 = DataFrame.fromArrays({ tag: ["Foo", "Bar", "Baz"] });
-evalDataFrame(df3, "lower(tag)");
+console.log(evalDataFrame(df3, "lower(tag)"));
 // Series ["foo", "bar", "baz"]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
diff --git a/playground/excel.html b/playground/excel.html
index 17450425..20468164 100644
--- a/playground/excel.html
+++ b/playground/excel.html
@@ -221,9 +221,9 @@ <h2>Advanced example</h2>
 const df3 = readExcel(buffer, { naValues: ["N/A", "MISSING", "-"] });
 
 // DataFrame operations work immediately
-df.describe();
-df.col("revenue").sum();
-df.groupby("region").mean();</textarea>
+console.log(df.describe());
+console.log(df.col("revenue").sum());
+console.log(df.groupby("region").mean());</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/fillna.html b/playground/fillna.html
index 503664b4..4f04fdeb 100644
--- a/playground/fillna.html
+++ b/playground/fillna.html
@@ -167,11 +167,11 @@ <h2>1 · Scalar fill</h2>
       <textarea class="playground-editor" spellcheck="false">import { Series, fillnaSeries } from "tsb";
 
 const s = new Series({ data: [1, null, null, 4] });
-fillnaSeries(s, { value: 0 }).values;
+console.log(fillnaSeries(s, { value: 0 }).values);
 // → [1, 0, 0, 4]
 
 const t = new Series({ data: [NaN, 2, NaN] });
-fillnaSeries(t, { value: 99 }).values;
+console.log(fillnaSeries(t, { value: 99 }).values);
 // → [99, 2, 99]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -194,12 +194,12 @@ <h2>2 · Forward fill (ffill / pad)</h2>
       <textarea class="playground-editor" spellcheck="false">import { Series, fillnaSeries } from "tsb";
 
 const s = new Series({ data: [null, 1, null, null, 4] });
-fillnaSeries(s, { method: "ffill" }).values;
+console.log(fillnaSeries(s, { method: "ffill" }).values);
 // → [null, 1, 1, 1, 4]
 
 // Trailing nulls are filled too
 const t = new Series({ data: [1, null, null] });
-fillnaSeries(t, { method: "ffill" }).values;
+console.log(fillnaSeries(t, { method: "ffill" }).values);
 // → [1, 1, 1]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -222,12 +222,12 @@ <h2>3 · Backward fill (bfill / backfill)</h2>
       <textarea class="playground-editor" spellcheck="false">import { Series, fillnaSeries } from "tsb";
 
 const s = new Series({ data: [null, null, 3, null, 5] });
-fillnaSeries(s, { method: "bfill" }).values;
+console.log(fillnaSeries(s, { method: "bfill" }).values);
 // → [3, 3, 3, 5, 5]
 
 // Leading nulls are filled from the first known value
 const t = new Series({ data: [null, null, 10] });
-fillnaSeries(t, { method: "bfill" }).values;
+console.log(fillnaSeries(t, { method: "bfill" }).values);
 // → [10, 10, 10]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -250,11 +250,11 @@ <h2>4 · Limiting the fill — limit</h2>
 
 // Only fill up to 1 consecutive missing value
 const s = new Series({ data: [1, null, null, null, 5] });
-fillnaSeries(s, { method: "ffill", limit: 1 }).values;
+console.log(fillnaSeries(s, { method: "ffill", limit: 1 }).values);
 // → [1, 1, null, null, 5]
 
 // bfill with limit=2
-fillnaSeries(s, { method: "bfill", limit: 2 }).values;
+console.log(fillnaSeries(s, { method: "bfill", limit: 2 }).values);
 // → [null, null, 5, 5, 5]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -281,8 +281,8 @@ <h2>5 · DataFrame — scalar fill</h2>
 });
 
 const result = fillnaDataFrame(df, { value: 0 });
-result.col("a").values; // [1, 0, 3]
-result.col("b").values; // [0, 2, 0]</textarea>
+console.log(result.col("a").values); // [1, 0, 3]
+console.log(result.col("b").values); // [0, 2, 0]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -309,9 +309,9 @@ <h2>6 · DataFrame — per-column fill map</h2>
 });
 
 const result = fillnaDataFrame(df, { value: { a: -1, b: 99 } });
-result.col("a").values; // [-1, 2, -1]
-result.col("b").values; // [1, 99, 3]
-result.col("c").values; // [null, null, null]  ← untouched</textarea>
+console.log(result.col("a").values); // [-1, 2, -1]
+console.log(result.col("b").values); // [1, 99, 3]
+console.log(result.col("c").values); // [null, null, null]  ← untouched</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -340,9 +340,9 @@ <h2>7 · DataFrame — method fill (axis=0 / axis=1)</h2>
 
 // axis=0 (default): ffill down each column
 const byCol = fillnaDataFrame(df, { method: "ffill" });
-byCol.col("a").values; // [1, 1, 1]
-byCol.col("b").values; // [null, 2, 2]
-byCol.col("c").values; // [null, null, 3]
+console.log(byCol.col("a").values); // [1, 1, 1]
+console.log(byCol.col("b").values); // [null, 2, 2]
+console.log(byCol.col("c").values); // [null, null, 3]
 
 // axis=1: bfill across each row
 const byRow = fillnaDataFrame(df, { method: "bfill", axis: 1 });
@@ -381,8 +381,8 @@ <h2>8 · DataFrame — fill values from a Series</h2>
 });
 
 const result = fillnaDataFrame(df, { value: fills });
-result.col("price").values;  // [10, 0, 30]
-result.col("volume").values; // [0, 200, 0]</textarea>
+console.log(result.col("price").values);  // [10, 0, 30]
+console.log(result.col("volume").values); // [0, 200, 0]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/filter.html b/playground/filter.html
index 55522997..df7fce5d 100644
--- a/playground/filter.html
+++ b/playground/filter.html
@@ -187,7 +187,7 @@ <h2>filterDataFrame — by items (column names)</h2>
       <textarea class="playground-editor" spellcheck="false">import { DataFrame, filterDataFrame } from "tsb";
 
 const df = DataFrame.fromColumns({ one: [1, 2], two: [3, 4], three: [5, 6] });
-filterDataFrame(df, { items: ["one", "three"] }).columns.values;
+console.log(filterDataFrame(df, { items: ["one", "three"] }).columns.values);
 // ["one", "three"]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -229,7 +229,7 @@ <h2>filterDataFrame — by like (substring)</h2>
       <textarea class="playground-editor" spellcheck="false">import { DataFrame, filterDataFrame } from "tsb";
 
 const df = DataFrame.fromColumns({ apple: [1], apricot: [2], banana: [3] });
-filterDataFrame(df, { like: "ap" }).columns.values;
+console.log(filterDataFrame(df, { like: "ap" }).columns.values);
 // ["apple", "apricot"]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -271,7 +271,7 @@ <h2>filterDataFrame — by regex</h2>
       <textarea class="playground-editor" spellcheck="false">import { DataFrame, filterDataFrame } from "tsb";
 
 const df = DataFrame.fromColumns({ a1: [1], a2: [2], b1: [3], b2: [4] });
-filterDataFrame(df, { regex: "^a" }).columns.values;
+console.log(filterDataFrame(df, { regex: "^a" }).columns.values);
 // ["a1", "a2"]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -316,7 +316,7 @@ <h2>filterDataFrame — filter rows (axis=0)</h2>
       <textarea class="playground-editor" spellcheck="false">import { DataFrame, filterDataFrame } from "tsb";
 
 const df = DataFrame.fromColumns({ x: [10, 20, 30] }, { index: ["foo", "bar", "baz"] });
-filterDataFrame(df, { like: "ba", axis: 0 }).index.values;
+console.log(filterDataFrame(df, { like: "ba", axis: 0 }).index.values);
 // ["bar", "baz"]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -358,7 +358,7 @@ <h2>filterSeries — by label</h2>
       <textarea class="playground-editor" spellcheck="false">import { Series, filterSeries } from "tsb";
 
 const s = new Series({ data: [1, 2, 3, 4], index: ["alpha", "beta", "gamma", "aleph"] });
-filterSeries(s, { like: "al" }).index.values;
+console.log(filterSeries(s, { like: "al" }).index.values);
 // ["alpha", "aleph"]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
diff --git a/playground/format_ops.html b/playground/format_ops.html
index 9865ec42..d8ce6c3d 100644
--- a/playground/format_ops.html
+++ b/playground/format_ops.html
@@ -173,9 +173,9 @@ <h2>Formatter factories</h2>
 const fmtPct     = makePercentFormatter(1);     // (v) =&gt; formatPercent(v, 1)
 const fmtDollar  = makeCurrencyFormatter("$");  // (v) =&gt; formatCurrency(v, "$", 2)
 
-fmtFloat(3.14159);   // "3.142"
-fmtPct(0.0825);      // "8.3%"
-fmtDollar(9999.99);  // "$9,999.99"</textarea>
+console.log(fmtFloat(3.14159));   // "3.142"
+console.log(fmtPct(0.0825));      // "8.3%"
+console.log(fmtDollar(9999.99));  // "$9,999.99"</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -196,7 +196,8 @@ <h2>Apply to a Series</h2>
 const returns = new Series({ data: [0.05, -0.02, 0.134, 0.007], name: "returns" });
 
 const formatted = applySeriesFormatter(returns, makePercentFormatter(1));
-// Series&lt;string&gt; ["5.0%", "-2.0%", "13.4%", "0.7%"]</textarea>
+// Series&lt;string&gt; ["5.0%", "-2.0%", "13.4%", "0.7%"]
+console.log(formatted);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -229,7 +230,8 @@ <h2>Apply to a DataFrame</h2>
 //   price:  ["$1,299.99", "$899.50", "$45.00"],
 //   change: ["2.50%", "-3.10%", "10.20%"],
 //   volume: ["15000", "8200", "230000"],      // no formatter → String(v)
-// }</textarea>
+// }
+console.log(formatted);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/infer_dtype.html b/playground/infer_dtype.html
index c49c0d17..b7d94f53 100644
--- a/playground/infer_dtype.html
+++ b/playground/infer_dtype.html
@@ -163,14 +163,14 @@ <h2>Example 1 — basic scalar types</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">import { inferDtype } from "tsb";
 
-inferDtype([1, 2, 3]);           // "integer"
-inferDtype([1.1, 2.2, 3.3]);     // "floating"
-inferDtype([1, 2.5, 3]);         // "mixed-integer-float"
-inferDtype([true, false, true]);  // "boolean"
-inferDtype(["a", "b", "c"]);     // "string"
-inferDtype([]);                  // "empty"
-inferDtype([null, null]);        // "empty"  (skipna=true by default)
-inferDtype([null, null], { skipna: false }); // "mixed"</textarea>
+console.log(inferDtype([1, 2, 3]));           // "integer"
+console.log(inferDtype([1.1, 2.2, 3.3]));     // "floating"
+console.log(inferDtype([1, 2.5, 3]));         // "mixed-integer-float"
+console.log(inferDtype([true, false, true]));  // "boolean"
+console.log(inferDtype(["a", "b", "c"]));     // "string"
+console.log(inferDtype([]));                  // "empty"
+console.log(inferDtype([null, null]));        // "empty"  (skipna=true by default)
+console.log(inferDtype([null, null], { skipna: false })); // "mixed"</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -189,13 +189,13 @@ <h2>Example 2 — working with Series</h2>
       <textarea class="playground-editor" spellcheck="false">import { Series, inferDtype } from "tsb";
 
 const s1 = new Series({ data: [10, 20, 30] });
-inferDtype(s1);   // "integer"
+console.log(inferDtype(s1));   // "integer"
 
 const s2 = new Series({ data: ["hello", "world"] });
-inferDtype(s2);   // "string"
+console.log(inferDtype(s2));   // "string"
 
 const s3 = new Series({ data: [1, null, 2, null, 3] });
-inferDtype(s3);   // "integer"  (nulls skipped by default)</textarea>
+console.log(inferDtype(s3));   // "integer"  (nulls skipped by default)</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -213,16 +213,16 @@ <h2>Example 3 — specialised tsb types</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">import { inferDtype, Timestamp, Timedelta, Period, Interval } from "tsb";
 
-inferDtype([Timestamp.fromtimestamp(0), Timestamp.fromtimestamp(1)]);
+console.log(inferDtype([Timestamp.fromtimestamp(0), Timestamp.fromtimestamp(1)]));
 // "datetime"
 
-inferDtype([Timedelta.fromComponents({ days: 1 }), Timedelta.fromComponents({ hours: 2 })]);
+console.log(inferDtype([Timedelta.fromComponents({ days: 1 }), Timedelta.fromComponents({ hours: 2 })]));
 // "timedelta"
 
-inferDtype([Period.fromDate(new Date("2024-01-01T00:00:00Z"), "M")]);
+console.log(inferDtype([Period.fromDate(new Date("2024-01-01T00:00:00Z"), "M")]));
 // "period"
 
-inferDtype([new Interval(0, 1), new Interval(1, 2)]);
+console.log(inferDtype([new Interval(0, 1), new Interval(1, 2)]));
 // "interval"</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -241,11 +241,11 @@ <h2>Example 4 — mixed types</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">import { inferDtype } from "tsb";
 
-inferDtype([1, "a", 2]);         // "mixed-integer" (int + non-numeric non-float)
-inferDtype(["a", true, null]);   // "mixed"         (string + bool)
-inferDtype([1n, 2n, 3n]);        // "integer"       (bigint only)
-inferDtype([1n, 2]);             // "decimal"       (bigint + integer)
-inferDtype([1n, 2.5]);           // "mixed-integer-float"</textarea>
+console.log(inferDtype([1, "a", 2]));         // "mixed-integer" (int + non-numeric non-float)
+console.log(inferDtype(["a", true, null]));   // "mixed"         (string + bool)
+console.log(inferDtype([1n, 2n, 3n]));        // "integer"       (bigint only)
+console.log(inferDtype([1n, 2]));             // "decimal"       (bigint + integer)
+console.log(inferDtype([1n, 2.5]));           // "mixed-integer-float"</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/infer_objects.html b/playground/infer_objects.html
index 2a0e6d1d..4b697337 100644
--- a/playground/infer_objects.html
+++ b/playground/infer_objects.html
@@ -166,19 +166,19 @@ <h2>inferObjectsSeries — promote object → typed</h2>
 
 // Object series holding integers
 const s = new Series({ data: [1, 2, 3], dtype: Dtype.object });
-s.dtype.kind;  // "object"
+console.log(s.dtype.kind);  // "object"
 
 const better = inferObjectsSeries(s);
-better.dtype.kind; // "int"
-better.values;     // [1, 2, 3]
+console.log(better.dtype.kind); // "int"
+console.log(better.values);     // [1, 2, 3]
 
 // Mixed types — cannot infer, returns original
 const mixed = new Series({ data: [1, "a", true], dtype: Dtype.object });
-inferObjectsSeries(mixed).dtype.kind; // "object"
+console.log(inferObjectsSeries(mixed).dtype.kind); // "object"
 
 // All null — no inference possible
 const nulls = new Series({ data: [null, null], dtype: Dtype.object });
-inferObjectsSeries(nulls).dtype.kind; // "object"</textarea>
+console.log(inferObjectsSeries(nulls).dtype.kind); // "object"</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -204,10 +204,10 @@ <h2>inferObjectsDataFrame — all columns at once</h2>
 });
 
 const inferred = inferObjectsDataFrame(df);
-inferred.col("ints").dtype.kind;   // "int"
-inferred.col("floats").dtype.kind; // "float"
-inferred.col("strs").dtype.kind;   // "string"
-inferred.col("bools").dtype.kind;  // "bool"</textarea>
+console.log(inferred.col("ints").dtype.kind);   // "int"
+console.log(inferred.col("floats").dtype.kind); // "float"
+console.log(inferred.col("strs").dtype.kind);   // "string"
+console.log(inferred.col("bools").dtype.kind);  // "bool"</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -228,21 +228,21 @@ <h2>convertDtypesSeries — also parses numeric strings</h2>
 // String values that look like integers
 const ints = new Series({ data: ["1", "2", "3"] });
 const result = convertDtypesSeries(ints);
-result.dtype.kind; // "int"
-result.values;     // [1, 2, 3]
+console.log(result.dtype.kind); // "int"
+console.log(result.values);     // [1, 2, 3]
 
 // String values that look like floats
 const floats = new Series({ data: ["1.5", "2.5", "3.5"] });
-convertDtypesSeries(floats).dtype.kind; // "float"
+console.log(convertDtypesSeries(floats).dtype.kind); // "float"
 
 // Non-numeric strings: unchanged
 const text = new Series({ data: ["apple", "banana"] });
-convertDtypesSeries(text);  // same Series, dtype "string"
+console.log(convertDtypesSeries(text));  // same Series, dtype "string"
 
 // Int series with nulls → can convert to float for NA safety
 import { Dtype } from "tsb";
 const withNull = new Series({ data: [1, null, 3], dtype: Dtype.int64 });
-convertDtypesSeries(withNull, { convertIntegerToFloat: true }).dtype.kind;
+console.log(convertDtypesSeries(withNull, { convertIntegerToFloat: true }).dtype.kind);
 // "float"  (null becomes NaN-compatible)</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -269,9 +269,9 @@ <h2>convertDtypesDataFrame — per-column conversion</h2>
 });
 
 const typed = convertDtypesDataFrame(raw);
-typed.col("age").dtype.kind;   // "int"
-typed.col("score").dtype.kind; // "float"
-typed.col("name").dtype.kind;  // "string" (unchanged — not numeric)</textarea>
+console.log(typed.col("age").dtype.kind);   // "int"
+console.log(typed.col("score").dtype.kind); // "float"
+console.log(typed.col("name").dtype.kind);  // "string" (unchanged — not numeric)</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/insert_pop.html b/playground/insert_pop.html
index 5cdfcfb5..ca7b4eb6 100644
--- a/playground/insert_pop.html
+++ b/playground/insert_pop.html
@@ -175,7 +175,8 @@ <h2>Example 1 — insertColumn</h2>
 // df2.col("city").values → ["NY", "LA", "SF"]
 
 // Original is unchanged
-// df.columns.values → ["name", "age"]</textarea>
+// df.columns.values → ["name", "age"]
+console.log(df2);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -197,7 +198,8 @@ <h2>Example 2 — Insert with a Series</h2>
 const salary = new Series({ data: [100_000, 90_000, 120_000], name: "salary" });
 
 const df2 = insertColumn(df, 0, "salary", salary);
-// df2.columns.values → ["salary", "a", "b"]</textarea>
+// df2.columns.values → ["salary", "a", "b"]
+console.log(df2);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -225,7 +227,8 @@ <h2>Example 3 — popColumn</h2>
 const { series: ageSeries, df: df2 } = popColumn(df, "age");
 // ageSeries.values       → [30, 25, 35]
 // df2.columns.values     → ["id", "name"]
-// df.columns.values      → ["id", "name", "age"]  ← original unchanged</textarea>
+// df.columns.values      → ["id", "name", "age"]  ← original unchanged
+console.log(df);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -251,7 +254,8 @@ <h2>Example 4 — reorderColumns</h2>
 
 // Select a subset (drops columns not listed)
 const df3 = reorderColumns(df, ["a", "c"]);
-// df3.columns.values → ["a", "c"]   (b and d are dropped)</textarea>
+// df3.columns.values → ["a", "c"]   (b and d are dropped)
+console.log(df3);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -278,7 +282,8 @@ <h2>Example 5 — moveColumn</h2>
 
 // Move "label" to the front
 const df2 = moveColumn(df, "label", 0);
-// df2.columns.values → ["label", "year", "value"]</textarea>
+// df2.columns.values → ["label", "year", "value"]
+console.log(df2);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -295,19 +300,19 @@ <h2>Error cases</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">// Duplicate column name (default: not allowed)
-insertColumn(df, 1, "a", [1, 2, 3]);
+console.log(insertColumn(df, 1, "a", [1, 2, 3]));
 // → RangeError: Column "a" already exists. Use allowDuplicates=true to permit...
 
 // Out-of-range loc
-insertColumn(df, 99, "x", [1, 2, 3]);
+console.log(insertColumn(df, 99, "x", [1, 2, 3]));
 // → RangeError: loc=99 is out of range [0, 2].
 
 // Wrong number of values
-insertColumn(df, 0, "x", [1]);  // df has 3 rows
+console.log(insertColumn(df, 0, "x", [1]));  // df has 3 rows
 // → RangeError: values length 1 does not match DataFrame row count 3.
 
 // Column not found
-popColumn(df, "missing");
+console.log(popColumn(df, "missing"));
 // → RangeError: Column "missing" not found in DataFrame.</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
diff --git a/playground/interpolate.html b/playground/interpolate.html
index e5d2d744..8302847f 100644
--- a/playground/interpolate.html
+++ b/playground/interpolate.html
@@ -172,7 +172,7 @@ <h2>1 · Linear interpolation (default)</h2>
 //                           0  1    2    3
 
 const filled = interpolateSeries(s);
-filled.values;
+console.log(filled.values);
 // → [1, 2, 3, 4]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -194,7 +194,7 @@ <h2>1 · Linear interpolation (default)</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">const t = new Series({ data: [null, 1, null, 3, null] });
 
-interpolateSeries(t).values;
+console.log(interpolateSeries(t).values);
 // → [null, 1, 2, 3, null]
 //    ^^^^              ^^^^
 //    leading          trailing
@@ -220,7 +220,7 @@ <h2>2 · Forward fill (ffill / pad / zero)</h2>
 
 const s = new Series({ data: [1, null, null, 4, null] });
 
-interpolateSeries(s, { method: "ffill" }).values;
+console.log(interpolateSeries(s, { method: "ffill" }).values);
 // → [1, 1, 1, 4, 4]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -243,7 +243,7 @@ <h2>3 · Backward fill (bfill / backfill)</h2>
 
 const s = new Series({ data: [null, 2, null, null, 5] });
 
-interpolateSeries(s, { method: "bfill" }).values;
+console.log(interpolateSeries(s, { method: "bfill" }).values);
 // → [2, 2, 5, 5, 5]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -270,7 +270,7 @@ <h2>4 · Nearest-neighbor</h2>
 // pos 2: dist-left=2, dist-right=1  → right wins → 4
 const s = new Series({ data: [1, null, null, 4] });
 
-interpolateSeries(s, { method: "nearest" }).values;
+console.log(interpolateSeries(s, { method: "nearest" }).values);
 // → [1, 1, 4, 4]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -292,7 +292,7 @@ <h2>4 · Nearest-neighbor</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">// Tie at equidistance: right wins
 const t = new Series({ data: [10, null, 30] });
-interpolateSeries(t, { method: "nearest" }).values;
+console.log(interpolateSeries(t, { method: "nearest" }).values);
 // → [10, 30, 30]   (pos 1 equidistant; right value 30 chosen)</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -318,15 +318,15 @@ <h2>5 · Limiting how many values are filled</h2>
 const s = new Series({ data: [0, null, null, null, 4] });
 
 // limit=1, forward: fill only the first NaN from the left
-interpolateSeries(s, { limit: 1 }).values;
+console.log(interpolateSeries(s, { limit: 1 }).values);
 // → [0, 1, null, null, 4]
 
 // limit=1, backward: fill only the last NaN from the right
-interpolateSeries(s, { limit: 1, limitDirection: "backward" }).values;
+console.log(interpolateSeries(s, { limit: 1, limitDirection: "backward" }).values);
 // → [0, null, null, 3, 4]
 
 // limit=1, both: fill one from each end
-interpolateSeries(s, { limit: 1, limitDirection: "both" }).values;
+console.log(interpolateSeries(s, { limit: 1, limitDirection: "both" }).values);
 // → [0, 1, null, 3, 4]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -353,8 +353,8 @@ <h2>6 · DataFrame — column-wise (axis=0, default)</h2>
 });
 
 const filled = dataFrameInterpolate(df);
-filled.col("temperature").values; // [20, 21, 22, 23]
-filled.col("humidity").values;    // [60, 65, 70, null]  ← trailing not filled</textarea>
+console.log(filled.col("temperature").values); // [20, 21, 22, 23]
+console.log(filled.col("humidity").values);    // [60, 65, 70, null]  ← trailing not filled</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -384,8 +384,8 @@ <h2>7 · DataFrame — row-wise (axis=1)</h2>
 // Row 0 interpolates 0 → 6  (linear, 4 steps)
 // Row 1 interpolates 10 → 22
 const filled = dataFrameInterpolate(df, { axis: 1 });
-filled.col("t1").values; // [2, 14]
-filled.col("t2").values; // [4, 18]</textarea>
+console.log(filled.col("t1").values); // [2, 14]
+console.log(filled.col("t2").values); // [4, 18]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/join.html b/playground/join.html
index 8ee935dc..143352d5 100644
--- a/playground/join.html
+++ b/playground/join.html
@@ -175,7 +175,7 @@ <h2>Left join (default)</h2>
   { index: ["alice", "charlie"] },
 );
 
-join(employees, salaries);
+console.log(join(employees, salaries));
 // dept          salary
 // alice    Engineering  90000
 // bob      Marketing    null    ← no salary for bob
@@ -195,13 +195,13 @@ <h2>Inner / outer / right join</h2>
           <button class="playground-reset">↺ Reset</button>
         </div>
       </div>
-      <textarea class="playground-editor" spellcheck="false">join(employees, salaries, { how: "inner" });
+      <textarea class="playground-editor" spellcheck="false">console.log(join(employees, salaries, { how: "inner" }));
 // Only alice and charlie (keys in BOTH DataFrames)
 
-join(employees, salaries, { how: "outer" });
+console.log(join(employees, salaries, { how: "outer" }));
 // All keys from either DataFrame (nulls where absent)
 
-join(employees, salaries, { how: "right" });
+console.log(join(employees, salaries, { how: "right" }));
 // All keys from salaries: alice and charlie</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -224,7 +224,7 @@ <h2>Overlapping columns — use lsuffix / rsuffix</h2>
 // This would throw — 'score' exists in both without suffix disambiguation:
 // join(a, b);
 
-join(a, b, { lsuffix: "_a", rsuffix: "_b" });
+console.log(join(a, b, { lsuffix: "_a", rsuffix: "_b" }));
 // score_a  score_b
 // x  10    15
 // y  20    25</textarea>
@@ -253,7 +253,7 @@ <h2>Join on a column key</h2>
 );
 
 // Join orders.customerId against customers index
-join(orders, customers, { on: "customerId", how: "left" });
+console.log(join(orders, customers, { on: "customerId", how: "left" }));
 // customerId  amount  name
 // C1          100     Alice
 // C2          200     Bob
@@ -279,7 +279,7 @@ <h2>joinAll — chain multiple joins</h2>
 const b1   = DataFrame.fromColumns({ B: [10,20,30] }, { index: ["K0","K1","K2"] });
 const b2   = DataFrame.fromColumns({ C: [100,200,300] }, { index: ["K0","K1","K2"] });
 
-joinAll(base, [b1, b2]);
+console.log(joinAll(base, [b1, b2]));
 // A  B   C
 // 1  10  100
 // 2  20  200
@@ -304,7 +304,7 @@ <h2>crossJoin — Cartesian product</h2>
 const colors = DataFrame.fromColumns({ color: ["red", "blue"] });
 const sizes  = DataFrame.fromColumns({ size:  ["S", "M", "L"] });
 
-crossJoin(colors, sizes);
+console.log(crossJoin(colors, sizes));
 // color  size
 // red    S
 // red    M
diff --git a/playground/json_normalize.html b/playground/json_normalize.html
index 5820aa06..ccc9a158 100644
--- a/playground/json_normalize.html
+++ b/playground/json_normalize.html
@@ -172,7 +172,8 @@ <h2>Example 1 — flatten nested dicts</h2>
 const df = jsonNormalize(data);
 // id  info.name  info.city
 // 1   Alice      NY
-// 2   Bob        LA</textarea>
+// 2   Bob        LA
+console.log(df);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -200,7 +201,8 @@ <h2>Example 2 — recordPath + meta</h2>
 // sku  qty  orderId  customer
 // X    2    A1       Alice
 // Y    1    A1       Alice
-// Z    5    B2       Bob</textarea>
+// Z    5    B2       Bob
+console.log(df);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -218,7 +220,7 @@ <h2>Example 3 — maxLevel</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">const data = [{ a: { b: { c: { d: 99 } } } }];
 
-jsonNormalize(data, { maxLevel: 1 });
+console.log(jsonNormalize(data, { maxLevel: 1 }));
 // a.b  →  {"c":{"d":99}}   (depth 2 is not expanded)</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
diff --git a/playground/math_ops.html b/playground/math_ops.html
index ba3f3726..232d571d 100644
--- a/playground/math_ops.html
+++ b/playground/math_ops.html
@@ -168,23 +168,23 @@ <h2>Code Examples</h2>
 
 // ── absSeries ────────────────────────────────────────────────────────────────
 const s = new Series({ data: [-1, 2, -3, null] });
-absSeries(s).values;   // [1, 2, 3, null]
+console.log(absSeries(s).values);   // [1, 2, 3, null]
 
 // ── absDataFrame ─────────────────────────────────────────────────────────────
 const df = DataFrame.fromColumns({ a: [-1, 2], b: [3, -4] });
-absDataFrame(df).col("a").values;  // [1, 2]
-absDataFrame(df).col("b").values;  // [3, 4]
+console.log(absDataFrame(df).col("a").values);  // [1, 2]
+console.log(absDataFrame(df).col("b").values);  // [3, 4]
 
 // ── roundSeries ──────────────────────────────────────────────────────────────
 const prices = new Series({ data: [1.234, 5.678, null] });
-roundSeries(prices, 2).values;    // [1.23, 5.68, null]
-roundSeries(prices, 0).values;    // [1, 6, null]
-roundSeries(prices, -1).values;   // nearest 10: [0, 10, null]
+console.log(roundSeries(prices, 2).values);    // [1.23, 5.68, null]
+console.log(roundSeries(prices, 0).values);    // [1, 6, null]
+console.log(roundSeries(prices, -1).values);   // nearest 10: [0, 10, null]
 
 // ── roundDataFrame ────────────────────────────────────────────────────────────
 const data = DataFrame.fromColumns({ price: [1.111, 2.222], qty: [3.7, 4.4] });
-roundDataFrame(data, 2).col("price").values;        // [1.11, 2.22]
-roundDataFrame(data, { price: 1, qty: 0 }).col("qty").values; // [4, 4]</textarea>
+console.log(roundDataFrame(data, 2).col("price").values);        // [1.11, 2.22]
+console.log(roundDataFrame(data, { price: 1, qty: 0 }).col("qty").values); // [4, 4]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/memory_usage.html b/playground/memory_usage.html
index 2956fb1d..faa9e18d 100644
--- a/playground/memory_usage.html
+++ b/playground/memory_usage.html
@@ -167,8 +167,8 @@ <h2>1 · Series memory_usage — fixed-width dtype</h2>
       <textarea class="playground-editor" spellcheck="false">const s = new Series({ data: [1, 2, 3, 4], dtype: Dtype.int32 });
 // int32 → 4 bytes/element × 4 = 16 bytes of data
 // RangeIndex → 3 × 8 = 24 bytes (only start/stop/step stored)
-seriesMemoryUsage(s);             // 40  (data + index)
-seriesMemoryUsage(s, { index: false }); // 16 (data only)</textarea>
+console.log(seriesMemoryUsage(s));             // 40  (data + index)
+console.log(seriesMemoryUsage(s, { index: false })); // 16 (data only)</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -186,9 +186,9 @@ <h2>2 · Series memory_usage — string dtype (shallow vs deep)</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">const s = new Series({ data: ["hello", "world", "tsb"], dtype: Dtype.string });
 // shallow: 3 × 8 bytes (one pointer per element)
-seriesMemoryUsage(s, { index: false });           // 24
+console.log(seriesMemoryUsage(s, { index: false }));           // 24
 // deep: actual char data — each string = length*2 + 56 bytes overhead
-seriesMemoryUsage(s, { index: false, deep: true }); // "hello"=66, "world"=66, "tsb"=62 → 194</textarea>
+console.log(seriesMemoryUsage(s, { index: false, deep: true })); // "hello"=66, "world"=66, "tsb"=62 → 194</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -214,7 +214,8 @@ <h2>3 · DataFrame memory_usage — per-column breakdown</h2>
 // Index (RangeIndex) → 24 bytes
 // id    (int32 × 3)  → 12 bytes
 // score (float64 × 3)→ 24 bytes
-// name  (string × 3, shallow) → 24 bytes</textarea>
+// name  (string × 3, shallow) → 24 bytes
+console.log(mu);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -235,7 +236,8 @@ <h2>4 · DataFrame memory_usage — deep=true for string columns</h2>
 });
 dataFrameMemoryUsage(df, { deep: true, index: false })
 // "short"                  → 5*2+56 = 66
-// "a slightly longer string" → 24*2+56 = 104</textarea>
+// "a slightly longer string" → 24*2+56 = 104
+console.log(df);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -256,7 +258,7 @@ <h2>5 · Total memory across all columns</h2>
   b: new Series({ data: Array.from({length: 1000}, (_,i) =&gt; i * 0.1), dtype: Dtype.float64 }),
 });
 const mu = dataFrameMemoryUsage(df, { index: false });
-mu.sum(); // 1000*8 + 1000*8 = 16000 bytes</textarea>
+console.log(mu.sum()); // 1000*8 + 1000*8 = 16000 bytes</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/merge_asof.html b/playground/merge_asof.html
index c48b422c..bd015293 100644
--- a/playground/merge_asof.html
+++ b/playground/merge_asof.html
@@ -179,7 +179,8 @@ <h2>Basic example — backward (default)</h2>
 // time | price | bid
 //    1 |   100 | null   ← no quote ≤ 1
 //    5 |   200 |   98   ← most recent quote ≤ 5 is at time=2
-//   10 |   300 |  195   ← most recent quote ≤ 10 is at time=6</textarea>
+//   10 |   300 |  195   ← most recent quote ≤ 10 is at time=6
+console.log(result);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -203,7 +204,8 @@ <h2>Forward direction</h2>
   on: "t",
   direction: "forward",
 });
-// t=1 → t=2 (w=20), t=3 → t=6 (w=60), t=7 → t=10 (w=100)</textarea>
+// t=1 → t=2 (w=20), t=3 → t=6 (w=60), t=7 → t=10 (w=100)
+console.log(result);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -223,7 +225,8 @@ <h2>Nearest direction</h2>
   on: "time",
   direction: "nearest",
 });
-// Picks the quote with the smallest absolute time difference.</textarea>
+// Picks the quote with the smallest absolute time difference.
+console.log(result);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -251,7 +254,7 @@ <h2>Grouping with by</h2>
   bid:    [99,   198,    109,   208],
 });
 
-mergeAsof(trades, quotes, { on: "time", by: "ticker" });</textarea>
+console.log(mergeAsof(trades, quotes, { on: "time", by: "ticker" }));</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -268,7 +271,7 @@ <h2>Tolerance</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">// Only match if the key distance is ≤ 2
-mergeAsof(left, right, { on: "t", tolerance: 2 });</textarea>
+console.log(mergeAsof(left, right, { on: "t", tolerance: 2 }));</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/merge_ordered.html b/playground/merge_ordered.html
index 4eb45e76..8f1a2c2f 100644
--- a/playground/merge_ordered.html
+++ b/playground/merge_ordered.html
@@ -181,7 +181,8 @@ <h2>Basic outer ordered merge</h2>
 //    2 |  null |    200
 //    3 |    30 |    300
 //    5 |    50 |   null
-//    6 |  null |    600</textarea>
+//    6 |  null |    600
+console.log(result);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -206,7 +207,8 @@ <h2>Forward-fill after merge</h2>
 //    2 |    10 |    200   ← price carried forward from date=1
 //    3 |    30 |    300
 //    5 |    50 |    300   ← volume carried forward from date=3
-//    6 |    50 |    600</textarea>
+//    6 |    50 |    600
+console.log(result);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -223,7 +225,7 @@ <h2>Inner join variant</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">// Only rows where both DataFrames have a key
-mergeOrdered(left, right, { on: "date", how: "inner" });
+console.log(mergeOrdered(left, right, { on: "date", how: "inner" }));
 // date | price | volume
 //    3 |    30 |    300</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
@@ -244,7 +246,7 @@ <h2>Different key column names per side</h2>
       <textarea class="playground-editor" spellcheck="false">const left2 = DataFrame.fromColumns({ t_left:  [1, 3, 5], a: [10, 30, 50] });
 const right2 = DataFrame.fromColumns({ t_right: [2, 3, 6], b: [200, 300, 600] });
 
-mergeOrdered(left2, right2, { left_on: "t_left", right_on: "t_right" });
+console.log(mergeOrdered(left2, right2, { left_on: "t_left", right_on: "t_right" }));
 // t_left | a    | b
 //      1 |   10 | null
 //      2 | null |  200
@@ -289,7 +291,8 @@ <h2>Group-wise ordered merge (left_by / right_by)</h2>
 //   A | 3 |   30 |   30
 //   B | 1 |  100 | null
 //   B | 2 | null |  200
-//   B | 3 |  300 |  300</textarea>
+//   B | 3 |  300 |  300
+console.log(right3);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -308,7 +311,7 @@ <h2>Overlapping non-key columns — suffixes</h2>
       <textarea class="playground-editor" spellcheck="false">const left4 = DataFrame.fromColumns({ k: [1, 2, 3], val: [10, 20, 30] });
 const right4 = DataFrame.fromColumns({ k: [2, 3, 4], val: [200, 300, 400] });
 
-mergeOrdered(left4, right4, { on: "k", suffixes: ["_L", "_R"] });
+console.log(mergeOrdered(left4, right4, { on: "k", suffixes: ["_L", "_R"] }));
 // k | val_L | val_R
 // 1 |    10 |  null
 // 2 |    20 |   200
diff --git a/playground/mode.html b/playground/mode.html
index eca873d3..9e7ca7be 100644
--- a/playground/mode.html
+++ b/playground/mode.html
@@ -162,7 +162,7 @@ <h2>1 · Single mode</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">const s = new Series({ data: [1, 2, 2, 3] });
-modeSeries(s).values;
+console.log(modeSeries(s).values);
 // → [2]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -180,7 +180,7 @@ <h2>2 · Tied modes — all returned sorted</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">const s = new Series({ data: [1, 1, 2, 2, 3] });
-modeSeries(s).values;
+console.log(modeSeries(s).values);
 // → [1, 2]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -198,7 +198,7 @@ <h2>3 · String values</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">const s = new Series({ data: ["cat", "dog", "dog", "bird"] });
-modeSeries(s).values;
+console.log(modeSeries(s).values);
 // → ["dog"]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -216,7 +216,7 @@ <h2>4 · Null values excluded (dropna=true default)</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">const s = new Series({ data: [null, 1, 1, null, null] });
-modeSeries(s).values;
+console.log(modeSeries(s).values);
 // → [1]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -234,7 +234,7 @@ <h2>5 · DataFrame column-wise (axis=0)</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">const df = DataFrame.fromColumns({ a: [1, 1, 2, 2], b: [5, 5, 5, 6] });
-modeDataFrame(df);
+console.log(modeDataFrame(df));
 // a: [1, 2], b: [5, null]  (null-padded)</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -252,7 +252,7 @@ <h2>6 · DataFrame row-wise (axis=1)</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">const df = DataFrame.fromColumns({ a: [1, 2], b: [1, 3], c: [2, 3] });
-modeDataFrame(df, { axis: 1 });
+console.log(modeDataFrame(df, { axis: 1 }));
 // row 0: mode=1, row 1: mode=3</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
diff --git a/playground/named_agg.html b/playground/named_agg.html
index 62fc72a5..4f3c69ee 100644
--- a/playground/named_agg.html
+++ b/playground/named_agg.html
@@ -182,7 +182,8 @@ <h2>Basic Usage</h2>
 // result:
 //         | total_salary | avg_salary | employees | avg_score
 // eng     | 330          | 110        | 3         | 4.167
-// hr      | 170          | 85         | 2         | 3.5</textarea>
+// hr      | 170          | 85         | 2         | 3.5
+console.log(result);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -227,7 +228,8 @@ <h2>Custom Aggregation Functions</h2>
 
 df.groupby("dept").aggNamed({
   salary_range: namedAgg("salary", salaryRange),
-});</textarea>
+});
+console.log(salaryRange);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/nancumops.html b/playground/nancumops.html
index 6e9d221a..009058fe 100644
--- a/playground/nancumops.html
+++ b/playground/nancumops.html
@@ -168,10 +168,10 @@ <h2>💡 Usage Examples</h2>
 
 const data = [1, 2, NaN, null, 3, 5];
 
-nansum(data);     // 11
-nanmean(data);    // 2.75
-nanmedian(data);  // 2.5
-nanstd(data);     // 1.708...</textarea>
+console.log(nansum(data));     // 11
+console.log(nanmean(data));    // 2.75
+console.log(nanmedian(data));  // 2.5
+console.log(nanstd(data));     // 1.708...</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -192,9 +192,9 @@ <h2>💡 Usage Examples</h2>
 
 const s = new Series({ data: [10, null, 30, NaN, 50] });
 
-nancount(s);  // 3
-nansum(s);    // 90
-nanmean(s);   // 30</textarea>
+console.log(nancount(s));  // 3
+console.log(nansum(s));    // 90
+console.log(nanmean(s));   // 30</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -216,12 +216,12 @@ <h2>💡 Usage Examples</h2>
 const xs = [2, 4, 4, 4, 5, 5, 7, 9];
 
 // Sample (ddof=1, default)
-nanvar(xs);           // ≈ 4.571
-nanstd(xs);           // ≈ 2.138
+console.log(nanvar(xs));           // ≈ 4.571
+console.log(nanstd(xs));           // ≈ 2.138
 
 // Population (ddof=0)
-nanvar(xs, { ddof: 0 });  // 4.0
-nanstd(xs, { ddof: 0 });  // 2.0</textarea>
+console.log(nanvar(xs, { ddof: 0 }));  // 4.0
+console.log(nanstd(xs, { ddof: 0 }));  // 2.0</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/natsort.html b/playground/natsort.html
index 5b2d3e94..a419c55b 100644
--- a/playground/natsort.html
+++ b/playground/natsort.html
@@ -194,11 +194,11 @@ <h2>2 · Options</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">// ignoreCase — text tokens are folded to lower-case
 const words = ["Banana", "apple", "Cherry"];
-natSorted(words, { ignoreCase: true });
+console.log(natSorted(words, { ignoreCase: true }));
 // → ["apple", "Banana", "Cherry"]
 
 // reverse — descending natural order
-natSorted(["file1", "file10", "file2"], { reverse: true });
+console.log(natSorted(["file1", "file10", "file2"], { reverse: true }));
 // → ["file10", "file2", "file1"]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -224,7 +224,7 @@ <h2>3 · Sorting objects with a key function</h2>
 // key extracts the string to sort by
 import { natSorted } from "tsb";
 const sorted = natSorted(rows, { key: r =&gt; r.path });
-sorted.map(r =&gt; r.path);
+console.log(sorted.map(r =&gt; r.path));
 // → ["img/photo1.jpg", "img/photo2.jpg", "img/photo10.jpg"]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -243,13 +243,13 @@ <h2>4 · natSortKey — inspect the token representation</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">import { natSortKey } from "tsb";
 
-natSortKey("file10.txt");   // → ["file", 10, ".txt"]
-natSortKey("007bonds");     // → [7, "bonds"]  (leading zeros stripped)
-natSortKey("abc");          // → ["abc"]
-natSortKey("42");           // → [42]
+console.log(natSortKey("file10.txt"));   // → ["file", 10, ".txt"]
+console.log(natSortKey("007bonds"));     // → [7, "bonds"]  (leading zeros stripped)
+console.log(natSortKey("abc"));          // → ["abc"]
+console.log(natSortKey("42"));           // → [42]
 
 // ignoreCase folds text tokens
-natSortKey("File10.TXT", { ignoreCase: true });
+console.log(natSortKey("File10.TXT", { ignoreCase: true }));
 // → ["file", 10, ".txt"]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -272,7 +272,7 @@ <h2>5 · natArgSort — permutation indices</h2>
 const idx = natArgSort(arr);
 // → [2, 1, 0]   (indices of "file1", "file2", "file10")
 
-idx.map(i =&gt; arr[i]);
+console.log(idx.map(i =&gt; arr[i]));
 // → ["file1", "file2", "file10"]
 
 // Use with a tsb Index to sort labels naturally:
@@ -300,7 +300,7 @@ <h2>6 · Comparison with lexicographic sort</h2>
 // → ["item1", "item12", "item2", "item20", "item3"]  ← wrong
 
 // Natural sort
-natSorted(data);
+console.log(natSorted(data));
 // → ["item1", "item2", "item3", "item12", "item20"]  ← correct</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
diff --git a/playground/notna.html b/playground/notna.html
index 60910600..719d3aaf 100644
--- a/playground/notna.html
+++ b/playground/notna.html
@@ -163,18 +163,18 @@ <h2>Example 1 — scalars</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">import { isna, notna } from "tsb";
 
-isna(null);       // true
-isna(undefined);  // true
-isna(NaN);        // true
+console.log(isna(null));       // true
+console.log(isna(undefined));  // true
+console.log(isna(NaN));        // true
 
-isna(0);          // false  — zero is not missing
-isna("");         // false  — empty string is not missing
-isna(false);      // false  — false is not missing
-isna(42);         // false
-isna("hello");    // false
+console.log(isna(0));          // false  — zero is not missing
+console.log(isna(""));         // false  — empty string is not missing
+console.log(isna(false));      // false  — false is not missing
+console.log(isna(42));         // false
+console.log(isna("hello"));    // false
 
-notna(null);      // false
-notna(42);        // true</textarea>
+console.log(notna(null));      // false
+console.log(notna(42));        // true</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -193,10 +193,10 @@ <h2>Example 2 — arrays</h2>
       <textarea class="playground-editor" spellcheck="false">import { isna, notna } from "tsb";
 
 const arr = [1, null, NaN, "x", undefined, false];
-isna(arr);
+console.log(isna(arr));
 // [false, true, true, false, true, false]
 
-notna(arr);
+console.log(notna(arr));
 // [true, false, false, true, false, true]
 
 // Count missing values
@@ -220,10 +220,10 @@ <h2>Example 3 — Series</h2>
 
 const s = new Series({ data: [10, null, NaN, 40], name: "sales" });
 
-isna(s).values;
+console.log(isna(s).values);
 // [false, true, true, false]
 
-notna(s).values;
+console.log(notna(s).values);
 // [true, false, false, true]
 
 // Filter to non-missing values
@@ -251,7 +251,7 @@ <h2>Example 4 — DataFrame</h2>
   active: [true,    false,   null   ],
 });
 
-isna(df).toRecords();
+console.log(isna(df).toRecords());
 // [
 //   { name: false, score: false, active: false },
 //   { name: true,  score: true,  active: false },
@@ -284,8 +284,8 @@ <h2>Example 5 — aliases</h2>
 
 // isnull is an alias for isna
 // notnull is an alias for notna
-isnull(null);     // true
-notnull("hello"); // true</textarea>
+console.log(isnull(null));     // true
+console.log(notnull("hello")); // true</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/notna_boolean.html b/playground/notna_boolean.html
index 79141124..e7486bf4 100644
--- a/playground/notna_boolean.html
+++ b/playground/notna_boolean.html
@@ -167,10 +167,10 @@ <h2>Code Examples</h2>
 const s = new Series({ data: [10, 20, 30, 40], index: ["a", "b", "c", "d"] });
 
 // Keep elements where mask is true
-keepTrue(s, [true, false, true, false]).values;  // [10, 30]
+console.log(keepTrue(s, [true, false, true, false]).values);  // [10, 30]
 
 // Keep elements where mask is false (complement)
-keepFalse(s, [true, false, true, false]).values; // [20, 40]
+console.log(keepFalse(s, [true, false, true, false]).values); // [20, 40]
 
 // Filter DataFrame rows
 const df = DataFrame.fromColumns(
@@ -178,11 +178,11 @@ <h2>Code Examples</h2>
   { index: ["alice", "bob", "carol", "dave"] },
 );
 const highScore = df.col("score").values.map((v) =&gt; (v as number) &gt;= 80);
-filterBy(df, highScore).col("age").values; // [25, 35]
+console.log(filterBy(df, highScore).col("age").values); // [25, 35]
 
 // Use a Series as a mask
 const mask = new Series({ data: [true, null, true, false], index: ["a", "b", "c", "d"] });
-keepTrue(s, mask).values; // [10, 30]  (null treated as false)</textarea>
+console.log(keepTrue(s, mask).values); // [10, 30]  (null treated as false)</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/notna_isna.html b/playground/notna_isna.html
index 7f73051e..b58c30c8 100644
--- a/playground/notna_isna.html
+++ b/playground/notna_isna.html
@@ -166,49 +166,49 @@ <h2>📝 Code examples</h2>
 import { Series, DataFrame } from "tsb";
 
 // ── scalar ──────────────────────────────────────────────────
-isna(null);          // true
-isna(undefined);     // true
-isna(NaN);           // true
-isna(0);             // false  — zero is not missing
-isna(false);         // false  — false is not missing
-isna("");            // false  — empty string is not missing
+console.log(isna(null));          // true
+console.log(isna(undefined));     // true
+console.log(isna(NaN));           // true
+console.log(isna(0));             // false  — zero is not missing
+console.log(isna(false));         // false  — false is not missing
+console.log(isna(""));            // false  — empty string is not missing
 
 // ── array ───────────────────────────────────────────────────
-isna([1, null, NaN, 3]);     // [false, true, true, false]
-notna([1, null, NaN, 3]);    // [true, false, false, true]
+console.log(isna([1, null, NaN, 3]));     // [false, true, true, false]
+console.log(notna([1, null, NaN, 3]));    // [true, false, false, true]
 
 // ── Series ──────────────────────────────────────────────────
 const s = new Series({ data: [1, null, NaN, 4] });
-isna(s).values;   // [false, true, true, false]
-notna(s).values;  // [true, false, false, true]
+console.log(isna(s).values);   // [false, true, true, false]
+console.log(notna(s).values);  // [true, false, false, true]
 
 // ── DataFrame ───────────────────────────────────────────────
 const df = new DataFrame(new Map([
   ["a", new Series({ data: [1, null, 3] })],
   ["b", new Series({ data: [NaN, 5, 6] })],
 ]));
-isna(df).col("a").values;  // [false, true, false]
-isna(df).col("b").values;  // [true, false, false]
+console.log(isna(df).col("a").values);  // [false, true, false]
+console.log(isna(df).col("b").values);  // [true, false, false]
 
 // ── aliases ─────────────────────────────────────────────────
-isnull(null);   // true  (same as isna)
-notnull(42);    // true  (same as notna)
+console.log(isnull(null));   // true  (same as isna)
+console.log(notnull(42));    // true  (same as notna)
 
 // ── fillna ──────────────────────────────────────────────────
-fillna([1, null, NaN, 4], { value: 0 });   // [1, 0, 0, 4]
-fillna(s, { value: -1 }).values;           // [1, -1, -1, 4]
-fillna(df, { value: 0 }).col("b").values;  // [0, 5, 6]
+console.log(fillna([1, null, NaN, 4], { value: 0 }));   // [1, 0, 0, 4]
+console.log(fillna(s, { value: -1 }).values);           // [1, -1, -1, 4]
+console.log(fillna(df, { value: 0 }).col("b").values);  // [0, 5, 6]
 
 // ── dropna ──────────────────────────────────────────────────
-dropna([1, null, NaN, 3]);   // [1, 3]
-dropna(s).values;            // [1, 4]
-dropna(df).shape;            // [2, 2]  (row 0 dropped because b[0]=NaN, row 1 dropped because a[1]=null)
-dropna(df, { how: "all" }).shape;         // drops only rows where ALL values are missing
-dropna(df, { axis: 1 }).columns.values;  // drops columns that contain any missing value
+console.log(dropna([1, null, NaN, 3]));   // [1, 3]
+console.log(dropna(s).values);            // [1, 4]
+console.log(dropna(df).shape);            // [2, 2]  (row 0 dropped because b[0]=NaN, row 1 dropped because a[1]=null)
+console.log(dropna(df, { how: "all" }).shape);         // drops only rows where ALL values are missing
+console.log(dropna(df, { axis: 1 }).columns.values);  // drops columns that contain any missing value
 
 // ── countna / countValid ─────────────────────────────────────
-countna([1, null, NaN, 3]);    // 2
-countValid([1, null, NaN, 3]); // 2</textarea>
+console.log(countna([1, null, NaN, 3]));    // 2
+console.log(countValid([1, null, NaN, 3])); // 2</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/numeric_extended.html b/playground/numeric_extended.html
index a399d8ad..d92ec244 100644
--- a/playground/numeric_extended.html
+++ b/playground/numeric_extended.html
@@ -179,7 +179,7 @@ <h2>digitize — bin values</h2>
 
 // Series version — preserves index
 const s = new Series({ data: [15, 45, 70], index: ["Alice","Bob","Carol"] });
-seriesDigitize(s, [33, 66, 100]);
+console.log(seriesDigitize(s, [33, 66, 100]));
 // Series: Alice→-1, Bob→1, Carol→2</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -208,7 +208,7 @@ <h2>histogram — frequency counts</h2>
 const { counts: d, binEdges: e } = histogram(data, { bins: 5, density: true });
 
 // Explicit edges
-histogram(data, { binEdges: [1, 4, 7, 10] });
+console.log(histogram(data, { binEdges: [1, 4, 7, 10] }));
 // counts: [ 3, 3, 4 ]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -229,19 +229,19 @@ <h2>linspace &amp; arange — number sequences</h2>
       <textarea class="playground-editor" spellcheck="false">import { linspace, arange } from "tsb";
 
 // 5 values from 0 to 1 (inclusive)
-linspace(0, 1, 5);
+console.log(linspace(0, 1, 5));
 // → [0, 0.25, 0.5, 0.75, 1]
 
 // 0..4
-arange(5);
+console.log(arange(5));
 // → [0, 1, 2, 3, 4]
 
 // From 2 to 10, step 2
-arange(2, 10, 2);
+console.log(arange(2, 10, 2));
 // → [2, 4, 6, 8]
 
 // Descending
-arange(5, 0, -1);
+console.log(arange(5, 0, -1));
 // → [5, 4, 3, 2, 1]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -265,9 +265,9 @@ <h2>percentileOfScore — percentile rank</h2>
 const grades = [55, 60, 70, 75, 80, 85, 90, 95];
 
 // What percentile is a score of 75?
-percentileOfScore(grades, 75);            // 50 (rank — default)
-percentileOfScore(grades, 75, "weak");    // 50 (≤ 75: 4/8 = 50%)
-percentileOfScore(grades, 75, "strict");  // 37.5 (&lt; 75: 3/8 = 37.5%)</textarea>
+console.log(percentileOfScore(grades, 75));            // 50 (rank — default)
+console.log(percentileOfScore(grades, 75, "weak"));    // 50 (≤ 75: 4/8 = 50%)
+console.log(percentileOfScore(grades, 75, "strict"));  // 37.5 (&lt; 75: 3/8 = 37.5%)</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -293,7 +293,8 @@ <h2>zscore — standardisation</h2>
 // z.values ≈ [-1.5, -0.5, -0.5, -0.5, 0, 0, 1, 2]
 
 // With population std (ddof=0)
-const zPop = zscore(s, { ddof: 0 });</textarea>
+const zPop = zscore(s, { ddof: 0 });
+console.log(zPop);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -314,11 +315,11 @@ <h2>minMaxNormalize — scale to [0, 1]</h2>
       <textarea class="playground-editor" spellcheck="false">import { minMaxNormalize, Series } from "tsb";
 
 const s = new Series({ data: [0, 25, 50, 75, 100] });
-minMaxNormalize(s).values;
+console.log(minMaxNormalize(s).values);
 // → [0, 0.25, 0.5, 0.75, 1]
 
 // Scale to [-1, 1]
-minMaxNormalize(s, { featureRangeMin: -1, featureRangeMax: 1 }).values;
+console.log(minMaxNormalize(s, { featureRangeMin: -1, featureRangeMax: 1 }).values);
 // → [-1, -0.5, 0, 0.5, 1]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -340,13 +341,13 @@ <h2>coefficientOfVariation — relative spread</h2>
       <textarea class="playground-editor" spellcheck="false">import { coefficientOfVariation, Series } from "tsb";
 
 // Dataset A: [10, 20, 30]  mean=20, std=10  → CV=0.5
-coefficientOfVariation(new Series({ data: [10, 20, 30] }));
+console.log(coefficientOfVariation(new Series({ data: [10, 20, 30] })));
 
 // Dataset B: [100, 200, 300]  same shape, higher scale  → CV=0.5
-coefficientOfVariation(new Series({ data: [100, 200, 300] }));
+console.log(coefficientOfVariation(new Series({ data: [100, 200, 300] })));
 
 // CV with population std
-coefficientOfVariation(new Series({ data: [1, 2, 3, 4, 5] }), { ddof: 0 });</textarea>
+console.log(coefficientOfVariation(new Series({ data: [1, 2, 3, 4, 5] }), { ddof: 0 }));</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/nunique.html b/playground/nunique.html
index 77c6fa17..8b7d4e8a 100644
--- a/playground/nunique.html
+++ b/playground/nunique.html
@@ -165,8 +165,8 @@ <h2>1 · nunique — count distinct values</h2>
 
 const s = new Series({ data: [1, 2, 2, 3, 3, 3, null] });
 
-nuniqueSeries(s);                 // 3 (null excluded by default)
-nuniqueSeries(s, { dropna: false }); // 4 (null counted as a distinct value)</textarea>
+console.log(nuniqueSeries(s));                 // 3 (null excluded by default)
+console.log(nuniqueSeries(s, { dropna: false })); // 4 (null counted as a distinct value)</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -187,12 +187,12 @@ <h2>2 · any — is any element truthy?</h2>
 const allZero = new Series({ data: [0, 0, 0] });
 const hasOne  = new Series({ data: [0, 0, 1] });
 
-anySeries(allZero); // false
-anySeries(hasOne);  // true
+console.log(anySeries(allZero)); // false
+console.log(anySeries(hasOne));  // true
 
 // With nulls (skipna=true by default)
 const withNull = new Series({ data: [null, 0, null] });
-anySeries(withNull); // false — null skipped, 0 is falsy</textarea>
+console.log(anySeries(withNull)); // false — null skipped, 0 is falsy</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -213,12 +213,12 @@ <h2>3 · all — are all elements truthy?</h2>
 const allTrue = new Series({ data: [1, 2, 3] });
 const hasFalsy = new Series({ data: [1, 0, 3] });
 
-allSeries(allTrue);  // true
-allSeries(hasFalsy); // false
+console.log(allSeries(allTrue));  // true
+console.log(allSeries(hasFalsy)); // false
 
 // Empty or all-null series vacuously returns true
-allSeries(new Series({ data: [] }));              // true
-allSeries(new Series({ data: [null, null] }));    // true</textarea>
+console.log(allSeries(new Series({ data: [] })));              // true
+console.log(allSeries(new Series({ data: [null, null] })));    // true</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -241,8 +241,8 @@ <h2>4 · DataFrame nunique</h2>
   value:    [1,   2,   1,   3  ],
 });
 
-nuniqueDataFrame(df);          // per-column: category→3, value→3
-nuniqueDataFrame(df, { axis: 1 }); // per-row: how many distinct values in each row</textarea>
+console.log(nuniqueDataFrame(df));          // per-column: category→3, value→3
+console.log(nuniqueDataFrame(df, { axis: 1 })); // per-row: how many distinct values in each row</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -265,12 +265,12 @@ <h2>5 · DataFrame any / all</h2>
   b: [1, 1, 1],
 });
 
-anyDataFrame(df2); // a: true, b: true  (each col has at least one truthy)
-allDataFrame(df2); // a: false, b: true (col a has a 0)
+console.log(anyDataFrame(df2)); // a: true, b: true  (each col has at least one truthy)
+console.log(allDataFrame(df2)); // a: false, b: true (col a has a 0)
 
 // axis=1: reduce across columns per row
-anyDataFrame(df2, { axis: 1 }); // row0: true, row1: true, row2: true
-allDataFrame(df2, { axis: 1 }); // row0: false, row1: false, row2: true</textarea>
+console.log(anyDataFrame(df2, { axis: 1 })); // row0: true, row1: true, row2: true
+console.log(allDataFrame(df2, { axis: 1 })); // row0: false, row1: false, row2: true</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/pipe_apply.html b/playground/pipe_apply.html
index 4a26f5bc..d6d2fa50 100644
--- a/playground/pipe_apply.html
+++ b/playground/pipe_apply.html
@@ -180,7 +180,8 @@ <h2>pipe — functional pipeline</h2>
   (x) =&gt; x * x,   // 16
   (x) =&gt; x - 1,   // 15
 );
-// n === 15</textarea>
+// n === 15
+console.log(n);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -214,7 +215,8 @@ <h2>seriesApply — element-wise apply</h2>
   new Series({ data: [10, 20, 30] }),
   (v, _label, pos) =&gt; (v as number) + pos * 100,
 );
-// [10, 120, 230]</textarea>
+// [10, 120, 230]
+console.log(withPos);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -249,7 +251,8 @@ <h2>dataFrameApply — column/row aggregation</h2>
   (row) =&gt; (row.at("score") as number) * (row.at("weight") as number),
   1,
 );
-// [85, 110.4, 62.4, 142.5]</textarea>
+// [85, 110.4, 62.4, 142.5]
+console.log(weightedScore);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -283,7 +286,8 @@ <h2>dataFrameApplyMap — element-wise cell transform</h2>
 // fn receives full context: (value, rowLabel, colName)
 const tagged = dataFrameApplyMap(df, (v, row, col) =&gt; `${col}[${row}]=${v}`);
 // a: ["a[0]=1", "a[1]=-2", "a[2]=3"]
-// b: ["b[0]=-4", "b[1]=5", "b[2]=-6"]</textarea>
+// b: ["b[0]=-4", "b[1]=5", "b[2]=-6"]
+console.log(tagged);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -328,7 +332,8 @@ <h2>dataFrameTransform — column-wise transform</h2>
     if (n &lt;= q3) return "Q3";
     return "Q4";
   });
-});</textarea>
+});
+console.log(binned);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -367,7 +372,8 @@ <h2>dataFrameTransformRows — row-wise transform</h2>
   last:  row["last"],
   score: row["score"],
   full:  `${row["first"]} ${row["last"]}`,
-}));</textarea>
+}));
+console.log(withFull);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -408,7 +414,8 @@ <h2>Combining pipe + apply</h2>
       typeof v === "number" ? Math.round(v * 100) / 100 : v
     )
   ),
-);</textarea>
+);
+console.log(clean);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/pivot_table.html b/playground/pivot_table.html
index 74be448f..66ec2b94 100644
--- a/playground/pivot_table.html
+++ b/playground/pivot_table.html
@@ -181,7 +181,8 @@ <h2>Example 1 — sales by region and product (sum + margins)</h2>
 //          A    B    All
 // North   220  200  420
 // South   150  430  580
-// All     370  630 1000</textarea>
+// All     370  630 1000
+console.log(result);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -216,7 +217,8 @@ <h2>Example 2 — mean aggregation with custom margins_name</h2>
 //       Jr   Sr   Total
 // Eng   70   90   80
 // Mkt   60   80   70
-// Total 65   85   75</textarea>
+// Total 65   85   75
+console.log(result);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -247,7 +249,8 @@ <h2>Example 3 — sort=false preserves insertion order</h2>
 });
 
 // Rows in order: Z, A, M  (insertion order)
-// Cols in order: b, a, c  (insertion order)</textarea>
+// Cols in order: b, a, c  (insertion order)
+console.log(df);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -280,7 +283,8 @@ <h2>Example 4 — count with margins</h2>
 //       Jr   Sr   All
 // Eng    1    2    3
 // Mkt    1    1    2
-// All    2    3    5</textarea>
+// All    2    3    5
+console.log(df);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/quantile.html b/playground/quantile.html
index 49c30941..849f0030 100644
--- a/playground/quantile.html
+++ b/playground/quantile.html
@@ -162,9 +162,9 @@ <h2>1 · Scalar quantile (median)</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">const s = new Series({ data: [1, 2, 3, 4, 5] });
-quantileSeries(s);          // default q=0.5 → 3
-quantileSeries(s, { q: 0.25 }); // → 2
-quantileSeries(s, { q: 0.75 }); // → 4</textarea>
+console.log(quantileSeries(s));          // default q=0.5 → 3
+console.log(quantileSeries(s, { q: 0.25 })); // → 2
+console.log(quantileSeries(s, { q: 0.75 })); // → 4</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -182,7 +182,8 @@ <h2>2 · Multiple quantile levels</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">const s = new Series({ data: [1, 2, 3, 4, 5] });
 const q = quantileSeries(s, { q: [0.25, 0.5, 0.75] });
-// Series indexed by q-values: { 0.25: 2, 0.5: 3, 0.75: 4 }</textarea>
+// Series indexed by q-values: { 0.25: 2, 0.5: 3, 0.75: 4 }
+console.log(q);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -200,11 +201,11 @@ <h2>3 · Interpolation methods</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">const s = new Series({ data: [0, 10] });
 // q=0.5 → position 0.5 between indices 0 and 1
-quantileSeries(s, { q: 0.5, interpolation: "linear" });   // 5
-quantileSeries(s, { q: 0.5, interpolation: "lower" });    // 0
-quantileSeries(s, { q: 0.5, interpolation: "higher" });   // 10
-quantileSeries(s, { q: 0.5, interpolation: "midpoint" }); // 5
-quantileSeries(s, { q: 0.5, interpolation: "nearest" });  // 0</textarea>
+console.log(quantileSeries(s, { q: 0.5, interpolation: "linear" }));   // 5
+console.log(quantileSeries(s, { q: 0.5, interpolation: "lower" }));    // 0
+console.log(quantileSeries(s, { q: 0.5, interpolation: "higher" }));   // 10
+console.log(quantileSeries(s, { q: 0.5, interpolation: "midpoint" })); // 5
+console.log(quantileSeries(s, { q: 0.5, interpolation: "nearest" }));  // 0</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -221,8 +222,8 @@ <h2>4 · NaN handling (skipna=true by default)</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">const s = new Series({ data: [1, null, 3, NaN, 5] });
-quantileSeries(s, { q: 0.5 });             // ignores null/NaN → 3
-quantileSeries(s, { q: 0.5, skipna: false }); // NaN propagates → NaN</textarea>
+console.log(quantileSeries(s, { q: 0.5 }));             // ignores null/NaN → 3
+console.log(quantileSeries(s, { q: 0.5, skipna: false })); // NaN propagates → NaN</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -239,10 +240,10 @@ <h2>5 · DataFrame — axis=0 (per-column quantiles)</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">const df = DataFrame.fromColumns({ a: [1, 2, 3, 4], b: [10, 20, 30, 40] });
-quantileDataFrame(df, { q: 0.5 });
+console.log(quantileDataFrame(df, { q: 0.5 }));
 // Series { a: 2.5, b: 25 }
 
-quantileDataFrame(df, { q: [0.25, 0.5, 0.75] });
+console.log(quantileDataFrame(df, { q: [0.25, 0.5, 0.75] }));
 // DataFrame 3×2: rows=[0.25, 0.5, 0.75], cols=[a, b]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -260,7 +261,7 @@ <h2>6 · DataFrame — axis=1 (per-row quantiles)</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">const df = DataFrame.fromColumns({ a: [1, 2, 3], b: [3, 4, 5], c: [5, 6, 7] });
-quantileDataFrame(df, { axis: 1, q: 0.5 });
+console.log(quantileDataFrame(df, { axis: 1, q: 0.5 }));
 // Series — median of each row: [3, 4, 5]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -278,7 +279,7 @@ <h2>7 · Q=[0, 0.25, 0.5, 0.75, 1] summary table</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">const df = DataFrame.fromColumns({ score: [55, 70, 80, 88, 92, 95, 99] });
-quantileDataFrame(df, { q: [0, 0.25, 0.5, 0.75, 1] });
+console.log(quantileDataFrame(df, { q: [0, 0.25, 0.5, 0.75, 1] }));
 // → summary statistics table</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
diff --git a/playground/reduce_ops.html b/playground/reduce_ops.html
index 993ae52c..8f481400 100644
--- a/playground/reduce_ops.html
+++ b/playground/reduce_ops.html
@@ -169,8 +169,8 @@ <h2>nuniqueSeries — count distinct values</h2>
       <textarea class="playground-editor" spellcheck="false">import { Series, nuniqueSeries } from "tsb";
 
 const s = new Series([1, 2, 2, null, 3]);
-nuniqueSeries(s);                    // 3   (null excluded by default)
-nuniqueSeries(s, { dropna: false }); // 4   (null counted as a distinct value)</textarea>
+console.log(nuniqueSeries(s));                    // 3   (null excluded by default)
+console.log(nuniqueSeries(s, { dropna: false })); // 4   (null counted as a distinct value)</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -193,7 +193,7 @@ <h2>nunique — count distinct per column (axis=0, default)</h2>
   rating: [5, 3, 5, 4],
   flag:   [true, false, true, null],
 });
-nunique(df);
+console.log(nunique(df));
 // Series { brand: 3, rating: 3, flag: 2 }</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -210,7 +210,7 @@ <h2>nunique — count distinct per row (axis=1)</h2>
           <button class="playground-reset">↺ Reset</button>
         </div>
       </div>
-      <textarea class="playground-editor" spellcheck="false">nunique(df, { axis: 1 });
+      <textarea class="playground-editor" spellcheck="false">console.log(nunique(df, { axis: 1 }));
 // Series [3, 3, 3, 3]  — each row has 3 distinct values</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -230,16 +230,16 @@ <h2>anySeries / allSeries</h2>
       <textarea class="playground-editor" spellcheck="false">import { Series, anySeries, allSeries } from "tsb";
 
 const flags = new Series([false, false, true]);
-anySeries(flags);  // true  — at least one truthy
-allSeries(flags);  // false — not all truthy
+console.log(anySeries(flags));  // true  — at least one truthy
+console.log(allSeries(flags));  // false — not all truthy
 
 const ones = new Series([1, 2, 3]);
-allSeries(ones);   // true  — all truthy
+console.log(allSeries(ones));   // true  — all truthy
 
 // skipna option
 const withNull = new Series([1, null, 2]);
-allSeries(withNull);                   // true  (null skipped)
-allSeries(withNull, { skipna: false }); // false (null is falsy)</textarea>
+console.log(allSeries(withNull));                   // true  (null skipped)
+console.log(allSeries(withNull, { skipna: false })); // false (null is falsy)</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -263,14 +263,14 @@ <h2>anyDataFrame / allDataFrame</h2>
   c: [0, 0, 0],
 });
 
-anyDataFrame(df2);
+console.log(anyDataFrame(df2));
 // Series { a: true, b: true, c: false }
 
-allDataFrame(df2);
+console.log(allDataFrame(df2));
 // Series { a: false, b: true, c: false }
 
 // axis=1: reduce across columns → one boolean per row
-anyDataFrame(df2, { axis: 1 });
+console.log(anyDataFrame(df2, { axis: 1 }));
 // Series [true, true, true]  (row 0: 0,1,0 → any=true via b)</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -293,7 +293,7 @@ <h2>boolOnly option</h2>
 });
 
 // Only consider boolean columns
-anyDataFrame(mixed, { boolOnly: true });
+console.log(anyDataFrame(mixed, { boolOnly: true }));
 // Series { flag: true }   — 'nums' column excluded</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
diff --git a/playground/reindex.html b/playground/reindex.html
index ac05172c..6e4860aa 100644
--- a/playground/reindex.html
+++ b/playground/reindex.html
@@ -166,19 +166,19 @@ <h2>1 · reindexSeries — basics</h2>
 const s = new Series({ data: [10, 20, 30], index: new Index(["a", "b", "c"]) });
 
 // Reorder labels
-reindexSeries(s, ["c", "a", "b"]).toArray();
+console.log(reindexSeries(s, ["c", "a", "b"]).toArray());
 // → [30, 10, 20]
 
 // Extend with new labels → null by default
-reindexSeries(s, ["a", "b", "c", "d"]).toArray();
+console.log(reindexSeries(s, ["a", "b", "c", "d"]).toArray());
 // → [10, 20, 30, null]
 
 // Extend with custom fill value
-reindexSeries(s, ["a", "b", "c", "d"], { fillValue: 0 }).toArray();
+console.log(reindexSeries(s, ["a", "b", "c", "d"], { fillValue: 0 }).toArray());
 // → [10, 20, 30, 0]
 
 // Drop labels
-reindexSeries(s, ["a", "c"]).toArray();
+console.log(reindexSeries(s, ["a", "c"]).toArray());
 // → [10, 30]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -203,21 +203,21 @@ <h2>2 · Fill methods</h2>
 });
 
 // Forward fill — carry last known value forward
-reindexSeries(temps, [0, 1, 2, 3, 4, 5], { method: "ffill" }).toArray();
+console.log(reindexSeries(temps, [0, 1, 2, 3, 4, 5], { method: "ffill" }).toArray());
 // → [15, 15, 18, 18, 18, 22]
 //       ^^       ^^ ^^      ← filled from left
 
 // Backward fill — carry next known value backward
-reindexSeries(temps, [0, 1, 2, 3, 4, 5], { method: "bfill" }).toArray();
+console.log(reindexSeries(temps, [0, 1, 2, 3, 4, 5], { method: "bfill" }).toArray());
 // → [15, 18, 18, 22, 22, 22]
 //       ^^       ^^  ^^  ← filled from right
 
 // Nearest — use closest value (prefer right on tie)
-reindexSeries(temps, [0, 1, 2, 3, 4, 5], { method: "nearest" }).toArray();
+console.log(reindexSeries(temps, [0, 1, 2, 3, 4, 5], { method: "nearest" }).toArray());
 // → [15, 15, 18, 18, 22, 22]
 
 // Limit — cap consecutive fills
-reindexSeries(temps, [0, 1, 2, 3, 4, 5], { method: "ffill", limit: 1 }).toArray();
+console.log(reindexSeries(temps, [0, 1, 2, 3, 4, 5], { method: "ffill", limit: 1 }).toArray());
 // → [15, 15, 18, null, null, 22]
 //       ^^       ^^ only 1 consecutive fill</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
@@ -244,11 +244,11 @@ <h2>3 · reindexDataFrame — rows</h2>
 // shape [3, 2], RangeIndex [0, 1, 2]
 
 // Extend to 5 rows — new rows filled with null
-reindexDataFrame(df, { index: [0, 1, 2, 3, 4] }).col("open").toArray();
+console.log(reindexDataFrame(df, { index: [0, 1, 2, 3, 4] }).col("open").toArray());
 // → [100, 102, 105, null, null]
 
 // Forward-fill new rows
-reindexDataFrame(df, { index: [0, 1, 2, 3, 4], method: "ffill" }).col("open").toArray();
+console.log(reindexDataFrame(df, { index: [0, 1, 2, 3, 4], method: "ffill" }).col("open").toArray());
 // → [100, 102, 105, 105, 105]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -270,12 +270,12 @@ <h2>4 · reindexDataFrame — columns</h2>
 const df = DataFrame.fromColumns({ a: [1, 2, 3], b: [4, 5, 6] });
 
 // Reorder columns
-reindexDataFrame(df, { columns: ["b", "a"] }).columns.toArray();
+console.log(reindexDataFrame(df, { columns: ["b", "a"] }).columns.toArray());
 // → ["b", "a"]
 
 // Add a new column filled with 0
 const r = reindexDataFrame(df, { columns: ["a", "b", "c"], fillValue: 0 });
-r.col("c").toArray();
+console.log(r.col("c").toArray());
 // → [0, 0, 0]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -305,8 +305,8 @@ <h2>5 · Reindex rows and columns simultaneously</h2>
   fillValue: -1,
 });
 // shape [4, 3]
-r.col("z").toArray();  // → [-1, -1, -1, -1]
-r.col("x").toArray();  // → [1, 2, 3, -1]</textarea>
+console.log(r.col("z").toArray());  // → [-1, -1, -1, -1]
+console.log(r.col("x").toArray());  // → [1, 2, 3, -1]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/rename_ops.html b/playground/rename_ops.html
index 8dbf1ad5..2317026b 100644
--- a/playground/rename_ops.html
+++ b/playground/rename_ops.html
@@ -177,37 +177,37 @@ <h2>Code Examples</h2>
 const s = new Series({ data: [1, 2, 3], index: ["a", "b", "c"] });
 
 // Record mapping — only matched labels are changed
-renameSeriesIndex(s, { a: "x", c: "z" }).index.values;  // ["x", "b", "z"]
+console.log(renameSeriesIndex(s, { a: "x", c: "z" }).index.values);  // ["x", "b", "z"]
 
 // Function mapper — called for every index label
-renameSeriesIndex(s, l =&gt; l.toUpperCase()).index.values; // ["A", "B", "C"]
+console.log(renameSeriesIndex(s, l =&gt; l.toUpperCase()).index.values); // ["A", "B", "C"]
 
 // ── renameDataFrame ──────────────────────────────────────────────────────────
 const df = DataFrame.fromColumns({ a: [1, 2], b: [3, 4] },
                                   { index: ["r0", "r1"] });
 
 // Rename columns
-renameDataFrame(df, { columns: { a: "x", b: "y" } }).columns.values; // ["x","y"]
+console.log(renameDataFrame(df, { columns: { a: "x", b: "y" } }).columns.values); // ["x","y"]
 
 // Rename row index
-renameDataFrame(df, { index: { r0: "row0", r1: "row1" } }).index.values;
+console.log(renameDataFrame(df, { index: { r0: "row0", r1: "row1" } }).index.values);
 
 // ── add_prefix / add_suffix ──────────────────────────────────────────────────
-addPrefixDataFrame(df, "col_").columns.values;         // ["col_a","col_b"]
-addSuffixDataFrame(df, "_v1").columns.values;          // ["a_v1","b_v1"]
+console.log(addPrefixDataFrame(df, "col_").columns.values);         // ["col_a","col_b"]
+console.log(addSuffixDataFrame(df, "_v1").columns.values);          // ["a_v1","b_v1"]
 
-addPrefixSeries(s, "idx_").index.values;               // ["idx_a","idx_b","idx_c"]
-addSuffixSeries(s, "_end").index.values;               // ["a_end","b_end","c_end"]
+console.log(addPrefixSeries(s, "idx_").index.values);               // ["idx_a","idx_b","idx_c"]
+console.log(addSuffixSeries(s, "_end").index.values);               // ["a_end","b_end","c_end"]
 
 // ── set_axis ─────────────────────────────────────────────────────────────────
-setAxisSeries(s, ["x", "y", "z"]).index.values;         // ["x","y","z"]
-setAxisDataFrame(df, ["col1","col2"], 1).columns.values; // ["col1","col2"]
-setAxisDataFrame(df, ["rowA","rowB"], 0).index.values;   // ["rowA","rowB"]
+console.log(setAxisSeries(s, ["x", "y", "z"]).index.values);         // ["x","y","z"]
+console.log(setAxisDataFrame(df, ["col1","col2"], 1).columns.values); // ["col1","col2"]
+console.log(setAxisDataFrame(df, ["rowA","rowB"], 0).index.values);   // ["rowA","rowB"]
 
 // ── to_frame ─────────────────────────────────────────────────────────────────
 const score = new Series({ data: [90, 80, 70], name: "score" });
-seriesToFrame(score).columns.values;          // ["score"]
-seriesToFrame(score, "points").columns.values; // ["points"]</textarea>
+console.log(seriesToFrame(score).columns.values);          // ["score"]
+console.log(seriesToFrame(score, "points").columns.values); // ["points"]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/rolling_apply.html b/playground/rolling_apply.html
index ecfcac0a..ff99fed7 100644
--- a/playground/rolling_apply.html
+++ b/playground/rolling_apply.html
@@ -179,7 +179,7 @@ <h2>1. rollingApply — Custom Function Per Window</h2>
 // Custom: range (max - min) over each 3-day window
 const range = (w) =&gt; Math.max(...w) - Math.min(...w);
 
-rollingApply(prices, 3, range).toArray();
+console.log(rollingApply(prices, 3, range).toArray());
 // [null, null, 2, 4, 4, 5]
 //  ↑↑ insufficient data (need 3 observations)</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
@@ -198,11 +198,11 @@ <h2>Options</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">// minPeriods=1 → start computing from the very first position
-rollingApply(prices, 3, range, { minPeriods: 1 }).toArray();
+console.log(rollingApply(prices, 3, range, { minPeriods: 1 }).toArray());
 // [0, 2, 2, 4, 4, 5]
 
 // center=true → symmetric window around each point
-rollingApply(prices, 3, range, { center: true }).toArray();
+console.log(rollingApply(prices, 3, range, { center: true }).toArray());
 // [null, 2, 4, 4, 5, null]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -235,7 +235,8 @@ <h2>2. rollingAgg — Multiple Aggregations at Once</h2>
 
 // result is a DataFrame with columns: "mean", "max", "min", "range"
 // result.col("mean").toArray() → [null, null, 2, 3, 4, 5, 6, 7]
-// result.col("range").toArray() → [null, null, 2, 2, 2, 2, 2, 2]</textarea>
+// result.col("range").toArray() → [null, null, 2, 2, 2, 2, 2, 2]
+console.log(result);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -263,7 +264,7 @@ <h2>3. dataFrameRollingApply — Apply Per Column</h2>
 // Pairwise range within each 2-step window per column
 const range = (w) =&gt; Math.max(...w) - Math.min(...w);
 
-dataFrameRollingApply(df, 2, range);
+console.log(dataFrameRollingApply(df, 2, range));
 //   open  close
 // 0 null  null
 // 1    2     2
@@ -304,7 +305,8 @@ <h2>4. dataFrameRollingAgg — Multi-Agg Per Column</h2>
 // A_sum:  [null, null, 6, 9, 12]
 // A_mean: [null, null, 2, 3,  4]
 // B_sum:  [null, null, 60, 90, 120]
-// B_mean: [null, null, 20, 30,  40]</textarea>
+// B_mean: [null, null, 20, 30,  40]
+console.log(out);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -342,7 +344,8 @@ <h2>Use case: Bollinger Band width</h2>
   const mean = stats.col("mean").toArray()[i];
   if (std === null || mean === null || mean === 0) return null;
   return (4 * (std as number)) / (mean as number);
-});</textarea>
+});
+console.log(bw);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/scalar_extract.html b/playground/scalar_extract.html
index 3f1554ca..bf8bbc13 100644
--- a/playground/scalar_extract.html
+++ b/playground/scalar_extract.html
@@ -190,8 +190,8 @@ <h2>squeezeSeries — extract scalar from a single-element Series</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">import { Series, squeezeSeries } from "tsb";
 
-squeezeSeries(new Series({ data: [42] }));     // 42
-squeezeSeries(new Series({ data: [1, 2, 3] })); // Series([1, 2, 3])</textarea>
+console.log(squeezeSeries(new Series({ data: [42] })));     // 42
+console.log(squeezeSeries(new Series({ data: [1, 2, 3] }))); // Series([1, 2, 3])</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -238,16 +238,16 @@ <h2>squeezeDataFrame — squeeze 1-D axis objects</h2>
       <textarea class="playground-editor" spellcheck="false">import { DataFrame, squeezeDataFrame } from "tsb";
 
 // 1×1 → scalar
-squeezeDataFrame(DataFrame.fromColumns({ A: [10] }));          // 10
+console.log(squeezeDataFrame(DataFrame.fromColumns({ A: [10] })));          // 10
 
 // 1 row, N cols → Series over columns
-squeezeDataFrame(DataFrame.fromColumns({ A: [1], B: [2] }));   // Series([1, 2])
+console.log(squeezeDataFrame(DataFrame.fromColumns({ A: [1], B: [2] })));   // Series([1, 2])
 
 // N rows, 1 col → Series over rows
-squeezeDataFrame(DataFrame.fromColumns({ A: [1, 2, 3] }));     // Series([1, 2, 3])
+console.log(squeezeDataFrame(DataFrame.fromColumns({ A: [1, 2, 3] })));     // Series([1, 2, 3])
 
 // axis=1: force squeeze along columns axis
-squeezeDataFrame(DataFrame.fromColumns({ A: [1, 2, 3] }), 1);  // Series([1, 2, 3])</textarea>
+console.log(squeezeDataFrame(DataFrame.fromColumns({ A: [1, 2, 3] }), 1));  // Series([1, 2, 3])</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -289,8 +289,8 @@ <h2>itemSeries — return the single element of a Series</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">import { Series, itemSeries } from "tsb";
 
-itemSeries(new Series({ data: [7] }));       // 7
-itemSeries(new Series({ data: [1, 2] }));    // throws RangeError</textarea>
+console.log(itemSeries(new Series({ data: [7] })));       // 7
+console.log(itemSeries(new Series({ data: [1, 2] })));    // throws RangeError</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -330,10 +330,10 @@ <h2>boolSeries / boolDataFrame — convert to boolean</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">import { Series, DataFrame, boolSeries, boolDataFrame } from "tsb";
 
-boolSeries(new Series({ data: [1] }));               // true
-boolSeries(new Series({ data: [0] }));               // false
-boolDataFrame(DataFrame.fromColumns({ A: [1] }));    // true
-boolDataFrame(DataFrame.fromColumns({ A: [false] })); // false</textarea>
+console.log(boolSeries(new Series({ data: [1] })));               // true
+console.log(boolSeries(new Series({ data: [0] })));               // false
+console.log(boolDataFrame(DataFrame.fromColumns({ A: [1] })));    // true
+console.log(boolDataFrame(DataFrame.fromColumns({ A: [false] }))); // false</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -378,11 +378,11 @@ <h2>firstValidIndex / lastValidIndex — find first/last non-NA label</h2>
       <textarea class="playground-editor" spellcheck="false">import { Series, firstValidIndex, lastValidIndex } from "tsb";
 
 const s = new Series({ data: [null, NaN, 3, 4], index: ["a", "b", "c", "d"] });
-firstValidIndex(s);   // "c"
-lastValidIndex(s);    // "d"
+console.log(firstValidIndex(s));   // "c"
+console.log(lastValidIndex(s));    // "d"
 
 const allNA = new Series({ data: [null, null] });
-firstValidIndex(allNA);  // null</textarea>
+console.log(firstValidIndex(allNA));  // null</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -427,8 +427,8 @@ <h2>dataFrameFirstValidIndex / dataFrameLastValidIndex</h2>
   A: [null, null, 1],
   B: [null, 2, 3],
 });
-dataFrameFirstValidIndex(df);  // 1
-dataFrameLastValidIndex(df);   // 2</textarea>
+console.log(dataFrameFirstValidIndex(df));  // 1
+console.log(dataFrameLastValidIndex(df));   // 2</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/select_dtypes.html b/playground/select_dtypes.html
index 1aebc52c..8c172170 100644
--- a/playground/select_dtypes.html
+++ b/playground/select_dtypes.html
@@ -253,7 +253,8 @@ <h2>6 · Interactive: try your own</h2>
   z: ["a", "b", "c"],
 });
 const result = selectDtypes(df, { include: "number" });
-return result.columns.toArray().join(", ");</textarea>
+return result.columns.toArray().join(", ");
+console.log(result);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/sem_var.html b/playground/sem_var.html
index 521c67b8..7dfbd2d4 100644
--- a/playground/sem_var.html
+++ b/playground/sem_var.html
@@ -165,7 +165,8 @@ <h2>1 · Sample variance (ddof=1)</h2>
 
 const s = new Series({ data: [2, 4, 4, 4, 5, 5, 7, 9] });
 varSeries(s);           // 4.0  (sample variance, ddof=1)
-varSeries(s, { ddof: 0 }); // 3.5  (population variance, ddof=0)</textarea>
+varSeries(s, { ddof: 0 }); // 3.5  (population variance, ddof=0)
+console.log(s);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -184,7 +185,7 @@ <h2>2 · Standard error of the mean</h2>
       <textarea class="playground-editor" spellcheck="false">import { semSeries } from "tsb";
 
 // SEM = sqrt(var / n)
-semSeries(s); // sqrt(4 / 8) ≈ 0.7071</textarea>
+console.log(semSeries(s)); // sqrt(4 / 8) ≈ 0.7071</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -204,7 +205,8 @@ <h2>3 · Handling missing values</h2>
 
 varSeries(s2);                 // skipna=true (default): ignores null
 varSeries(s2, { skipna: false }); // propagates NaN when null present
-varSeries(s2, { minCount: 5 });   // NaN: need 5 valid values but only 4</textarea>
+varSeries(s2, { minCount: 5 });   // NaN: need 5 valid values but only 4
+console.log(s2);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -228,7 +230,7 @@ <h2>4 · DataFrame column-wise variance</h2>
 });
 
 varDataFrame(df);          // Series { a: 1, b: 100 }
-semDataFrame(df);          // Series { a: sqrt(1/3), b: sqrt(100/3) }
+console.log(semDataFrame(df));          // Series { a: sqrt(1/3), b: sqrt(100/3) }
 varDataFrame(df, { axis: 1 }); // row-wise variance</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -251,7 +253,8 @@ <h2>5 · numericOnly — skip non-numeric columns</h2>
 });
 
 varDataFrame(df2, { numericOnly: true });
-// Only includes "score", excludes "label"</textarea>
+// Only includes "score", excludes "label"
+console.log(df2);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/skew_kurt.html b/playground/skew_kurt.html
index 3157da85..d326c945 100644
--- a/playground/skew_kurt.html
+++ b/playground/skew_kurt.html
@@ -162,7 +162,7 @@ <h2>1 · Symmetric distribution — skew ≈ 0</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">const s = new Series({ data: [1, 2, 3, 4, 5] });
-skewSeries(s);
+console.log(skewSeries(s));
 // → 0</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -180,7 +180,7 @@ <h2>2 · Right-skewed distribution — positive skew</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">const s = new Series({ data: [1, 2, 3, 4, 100] });
-skewSeries(s);
+console.log(skewSeries(s));
 // → large positive value</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -198,7 +198,7 @@ <h2>3 · Kurtosis — uniform-like (platykurtic, negative excess)</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">const s = new Series({ data: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] });
-kurtSeries(s);
+console.log(kurtSeries(s));
 // → negative (flatter than normal)</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -215,8 +215,8 @@ <h2>4 · NaN propagation — too few values</h2>
           <button class="playground-reset">↺ Reset</button>
         </div>
       </div>
-      <textarea class="playground-editor" spellcheck="false">skewSeries(new Series({ data: [1, 2] }));  // NaN — need ≥ 3
-kurtSeries(new Series({ data: [1, 2, 3] })); // NaN — need ≥ 4</textarea>
+      <textarea class="playground-editor" spellcheck="false">console.log(skewSeries(new Series({ data: [1, 2] })));  // NaN — need ≥ 3
+console.log(kurtSeries(new Series({ data: [1, 2, 3] }))); // NaN — need ≥ 4</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -236,7 +236,7 @@ <h2>5 · DataFrame column-wise skewness</h2>
   symmetric: [1, 2, 3, 4, 5],
   right_skew: [1, 2, 3, 4, 100],
 });
-skewDataFrame(df).values;</textarea>
+console.log(skewDataFrame(df).values);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -255,7 +255,7 @@ <h2>6 · DataFrame row-wise kurtosis</h2>
       <textarea class="playground-editor" spellcheck="false">const df = DataFrame.fromColumns({
   a: [1, 10], b: [2, 10], c: [3, 10], d: [4, 10], e: [100, 10], f: [5, 10],
 });
-kurtDataFrame(df, { axis: 1 }).values;</textarea>
+console.log(kurtDataFrame(df, { axis: 1 }).values);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/sort_ops.html b/playground/sort_ops.html
index 9c9ba9f4..1d5ed930 100644
--- a/playground/sort_ops.html
+++ b/playground/sort_ops.html
@@ -194,9 +194,9 @@ <h2>sortValuesSeries — sort a Series by its values</h2>
 
 const s = new Series({ data: [3, 1, 2], index: ["b", "a", "c"] });
 
-sortValuesSeries(s);                      // [1, 2, 3] index: ["a","c","b"]
-sortValuesSeries(s, { ascending: false }); // [3, 2, 1] index: ["b","c","a"]
-sortValuesSeries(s, { ignoreIndex: true }); // resets index to [0, 1, 2]</textarea>
+console.log(sortValuesSeries(s));                      // [1, 2, 3] index: ["a","c","b"]
+console.log(sortValuesSeries(s, { ascending: false })); // [3, 2, 1] index: ["b","c","a"]
+console.log(sortValuesSeries(s, { ignoreIndex: true })); // resets index to [0, 1, 2]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -233,8 +233,8 @@ <h2>NaN / null handling</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">const s2 = new Series({ data: [3, null, 1] });
-sortValuesSeries(s2);                           // [1, 3, null]
-sortValuesSeries(s2, { naPosition: "first" }); // [null, 1, 3]</textarea>
+console.log(sortValuesSeries(s2));                           // [1, 3, null]
+console.log(sortValuesSeries(s2, { naPosition: "first" })); // [null, 1, 3]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -271,7 +271,7 @@ <h2>sortIndexSeries — sort a Series by its index labels</h2>
       <textarea class="playground-editor" spellcheck="false">import { sortIndexSeries } from "tsb";
 
 const s = new Series({ data: [3, 1, 2], index: ["b", "a", "c"] });
-sortIndexSeries(s);
+console.log(sortIndexSeries(s));
 // values: [1, 3, 2], index: ["a", "b", "c"]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -317,10 +317,10 @@ <h2>sortValuesDataFrame — sort DataFrame rows by column values</h2>
 
 const df = DataFrame.fromColumns({ a: [3, 1, 2], b: [10, 30, 20] });
 
-sortValuesDataFrame(df, "a");
+console.log(sortValuesDataFrame(df, "a"));
 // col a: [1, 2, 3]  col b: [30, 20, 10]
 
-sortValuesDataFrame(df, ["a", "b"], { ascending: [true, false] });
+console.log(sortValuesDataFrame(df, ["a", "b"], { ascending: [true, false] }));
 // compound sort: by a ascending, then b descending</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -359,11 +359,11 @@ <h2>sortIndexDataFrame — sort DataFrame rows (or columns) by index</h2>
       <textarea class="playground-editor" spellcheck="false">import { sortIndexDataFrame } from "tsb";
 
 const df2 = DataFrame.fromColumns({ z: [1], a: [2], m: [3] });
-sortIndexDataFrame(df2, { axis: 1 });
+console.log(sortIndexDataFrame(df2, { axis: 1 }));
 // columns in alphabetical order: "a", "m", "z"
 
 const df3 = DataFrame.fromColumns({ v: [1, 2, 3] }, { index: ["c", "a", "b"] });
-sortIndexDataFrame(df3);
+console.log(sortIndexDataFrame(df3));
 // rows in index order: "a" (2), "b" (3), "c" (1)</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
diff --git a/playground/str_findall_and_json_denormalize.html b/playground/str_findall_and_json_denormalize.html
index a8a9e94e..a8a2e70c 100644
--- a/playground/str_findall_and_json_denormalize.html
+++ b/playground/str_findall_and_json_denormalize.html
@@ -183,8 +183,8 @@ <h2>1. strFindall — all regex matches per element</h2>
 // ]
 
 // Parse the JSON to get actual arrays:
-JSON.parse(allPrices.values[0]); // ["$10.99", "$5.00"]
-JSON.parse(allPrices.values[1]); // []</textarea>
+console.log(JSON.parse(allPrices.values[0])); // ["$10.99", "$5.00"]
+console.log(JSON.parse(allPrices.values[1])); // []</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -205,7 +205,8 @@ <h2>With capture groups</h2>
 const names = strFindall(s, /name: (\w+)/);
 // Series ['["Alice"]', '["Bob"]', '[]']
 
-// First capture group is extracted (pandas behaviour)</textarea>
+// First capture group is extracted (pandas behaviour)
+console.log(names);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -224,7 +225,8 @@ <h2>Null / NaN handling</h2>
       <textarea class="playground-editor" spellcheck="false">const s = new Series({ data: ['hello', null, NaN, 'world'] });
 const result = strFindall(s, /\w+/);
 // Series ['["hello"]', null, null, '["world"]']
-// Null/NaN elements return null (not []) — matches pandas</textarea>
+// Null/NaN elements return null (not []) — matches pandas
+console.log(result);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -248,7 +250,7 @@ <h2>2. strFindallCount — count matches per element</h2>
 
 // Count vowels per word
 const vowels = new Series({ data: ['beautiful', 'rhythm', 'aeiou'] });
-strFindallCount(vowels, /[aeiou]/i);
+console.log(strFindallCount(vowels, /[aeiou]/i));
 // Series [5, 0, 5]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -278,7 +280,8 @@ <h2>3. strFindFirst — first match per element</h2>
 
 // Extract just the year (first capture group)
 const years = strFindFirst(logs, /(\d{4})-\d{2}-\d{2}/);
-// Series ['2024', '2024', null]</textarea>
+// Series ['2024', '2024', null]
+console.log(years);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -311,7 +314,8 @@ <h2>4. strFindallExpand — expand capture groups into a DataFrame</h2>
 //    0     1
 // 0  John  30
 // 1  Jane  25
-// 2  null  null</textarea>
+// 2  null  null
+console.log(df2);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -354,7 +358,8 @@ <h2>5. toJsonDenormalize — flat DataFrame → nested JSON</h2>
 ];
 const df = jsonNormalize(original);
 const recovered = toJsonDenormalize(df);
-// recovered ≈ original (with the same structure)</textarea>
+// recovered ≈ original (with the same structure)
+console.log(recovered);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -375,7 +380,7 @@ <h2>Custom separator</h2>
   'user__name': ['Alice'],
   'user__city': ['NYC'],
 });
-toJsonDenormalize(df2, { sep: '__' });
+console.log(toJsonDenormalize(df2, { sep: '__' }));
 // [{ user: { name: 'Alice', city: 'NYC' } }]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -393,7 +398,7 @@ <h2>Drop null values</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">const df3 = DataFrame.fromColumns({ a: [1, null], b: [null, 2] });
-toJsonDenormalize(df3, { dropNull: true });
+console.log(toJsonDenormalize(df3, { dropNull: true }));
 // [{ a: 1 }, { b: 2 }]  ← null fields are omitted</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -412,7 +417,7 @@ <h2>toJsonRecords — orient="records"</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">import { toJsonRecords } from 'tsb';
 const df = DataFrame.fromColumns({ a: [1, 2], b: ['x', 'y'] });
-toJsonRecords(df);
+console.log(toJsonRecords(df));
 // [{ a: 1, b: 'x' }, { a: 2, b: 'y' }]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -430,10 +435,10 @@ <h2>toJsonSplit — orient="split"</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">import { toJsonSplit } from 'tsb';
-toJsonSplit(df);
+console.log(toJsonSplit(df));
 // { columns: ['a', 'b'], index: [0, 1], data: [[1, 'x'], [2, 'y']] }
 
-toJsonSplit(df, { includeIndex: false });
+console.log(toJsonSplit(df, { includeIndex: false }));
 // { columns: ['a', 'b'], data: [[1, 'x'], [2, 'y']] }</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -451,7 +456,7 @@ <h2>toJsonIndex — orient="index"</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">import { toJsonIndex } from 'tsb';
-toJsonIndex(df);
+console.log(toJsonIndex(df));
 // { '0': { a: 1, b: 'x' }, '1': { a: 2, b: 'y' } }
 
 // With custom string index
@@ -459,7 +464,7 @@ <h2>toJsonIndex — orient="index"</h2>
   { v: [10, 20] },
   { index: ['alice', 'bob'] }
 );
-toJsonIndex(df2);
+console.log(toJsonIndex(df2));
 // { alice: { v: 10 }, bob: { v: 20 } }</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
diff --git a/playground/style.html b/playground/style.html
index c7ff9071..5afd7a6c 100644
--- a/playground/style.html
+++ b/playground/style.html
@@ -183,7 +183,8 @@ <h2>Overview</h2>
   .setTableStyles([
     { selector: "th", props: { "background-color": "#343a40", color: "#fff" } },
   ])
-  .toHtml();</textarea>
+  .toHtml();
+console.log(html);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -235,7 +236,8 @@ <h2>Factory function</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">const styler = dataFrameStyle(df);
 // Equivalent to: new Styler(df)
-// Equivalent to: df.style  (in pandas)</textarea>
+// Equivalent to: df.style  (in pandas)
+console.log(styler);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -252,10 +254,10 @@ <h2>.format(formatter, subset?, naRep?)</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">// Function formatter
-dataFrameStyle(df).format((v) =&gt; typeof v === "number" ? `$${v.toFixed(2)}` : String(v));
+console.log(dataFrameStyle(df).format((v) =&gt; typeof v === "number" ? `$${v.toFixed(2)}` : String(v)));
 
 // Template string (replaces {v} with the cell value)
-dataFrameStyle(df).format("{v}%", ["pct_col"]);
+console.log(dataFrameStyle(df).format("{v}%", ["pct_col"]));
 
 // Only format specific columns
 dataFrameStyle(df).format(
@@ -264,7 +266,7 @@ <h2>.format(formatter, subset?, naRep?)</h2>
 );
 
 // null formatter resets to default
-dataFrameStyle(df).format(null);</textarea>
+console.log(dataFrameStyle(df).format(null));</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -281,7 +283,7 @@ <h2>.formatIndex(formatter)</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">// Format the row index labels
-dataFrameStyle(df).formatIndex((v) =&gt; `[${String(v)}]`);</textarea>
+console.log(dataFrameStyle(df).formatIndex((v) =&gt; `[${String(v)}]`));</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -298,7 +300,7 @@ <h2>.setPrecision(n)</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">// Show 2 decimal places by default
-dataFrameStyle(df).setPrecision(2);</textarea>
+console.log(dataFrameStyle(df).setPrecision(2));</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -315,7 +317,7 @@ <h2>.setNaRep(str)</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">// Show "N/A" for missing values
-dataFrameStyle(df).setNaRep("N/A");</textarea>
+console.log(dataFrameStyle(df).setNaRep("N/A"));</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -342,8 +344,8 @@ <h2>.apply(fn, axis?, subset?)</h2>
 );
 
 // String axis aliases
-dataFrameStyle(df).apply(fn, "index");   // same as axis=0
-dataFrameStyle(df).apply(fn, "columns"); // same as axis=1</textarea>
+console.log(dataFrameStyle(df).apply(fn, "index"));   // same as axis=0
+console.log(dataFrameStyle(df).apply(fn, "columns")); // same as axis=1</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -365,7 +367,7 @@ <h2>.applymap(fn, subset?) / .map(fn, subset?)</h2>
 );
 
 // .map() is an alias
-dataFrameStyle(df).map((v) =&gt; v === null ? "background-color: #ffeeee;" : "");</textarea>
+console.log(dataFrameStyle(df).map((v) =&gt; v === null ? "background-color: #ffeeee;" : ""));</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -382,7 +384,7 @@ <h2>.setProperties(props, subset?)</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">// Apply CSS to all cells (or a subset)
-dataFrameStyle(df).setProperties({ "font-weight": "bold", color: "navy" }, ["important"]);</textarea>
+console.log(dataFrameStyle(df).setProperties({ "font-weight": "bold", color: "navy" }, ["important"]));</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -437,7 +439,7 @@ <h2>.highlightNull(color?, subset?)</h2>
           <button class="playground-reset">↺ Reset</button>
         </div>
       </div>
-      <textarea class="playground-editor" spellcheck="false">dataFrameStyle(df).highlightNull("orange");    // default color: "red"</textarea>
+      <textarea class="playground-editor" spellcheck="false">console.log(dataFrameStyle(df).highlightNull("orange"));    // default color: "red"</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -501,7 +503,7 @@ <h2>.textGradient(options?)</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">// Same as backgroundGradient but applies to text color instead
-dataFrameStyle(df).textGradient({ cmap: "RdYlGn" });</textarea>
+console.log(dataFrameStyle(df).textGradient({ cmap: "RdYlGn" }));</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -540,7 +542,7 @@ <h2>.setCaption(text)</h2>
           <button class="playground-reset">↺ Reset</button>
         </div>
       </div>
-      <textarea class="playground-editor" spellcheck="false">dataFrameStyle(df).setCaption("Q3 Sales Report");</textarea>
+      <textarea class="playground-editor" spellcheck="false">console.log(dataFrameStyle(df).setCaption("Q3 Sales Report"));</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -578,7 +580,7 @@ <h2>.setTableAttributes(attrs)</h2>
           <button class="playground-reset">↺ Reset</button>
         </div>
       </div>
-      <textarea class="playground-editor" spellcheck="false">dataFrameStyle(df).setTableAttributes('class="report-table" id="q3-report"');</textarea>
+      <textarea class="playground-editor" spellcheck="false">console.log(dataFrameStyle(df).setTableAttributes('class="report-table" id="q3-report"'));</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -594,10 +596,10 @@ <h2>.hide(axis?, subset?)</h2>
           <button class="playground-reset">↺ Reset</button>
         </div>
       </div>
-      <textarea class="playground-editor" spellcheck="false">dataFrameStyle(df).hide(0);                // hide row index
-dataFrameStyle(df).hide("index");           // same
-dataFrameStyle(df).hide(1, ["col_a"]);      // hide specific columns
-dataFrameStyle(df).hide("columns", ["b"]); // same</textarea>
+      <textarea class="playground-editor" spellcheck="false">console.log(dataFrameStyle(df).hide(0));                // hide row index
+console.log(dataFrameStyle(df).hide("index"));           // same
+console.log(dataFrameStyle(df).hide(1, ["col_a"]));      // hide specific columns
+console.log(dataFrameStyle(df).hide("columns", ["b"])); // same</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -618,7 +620,8 @@ <h2>.toHtml(uuid?) / .render(uuid?)</h2>
   .toHtml();         // .render() is an alias
 
 // Inject into a page
-document.getElementById("output").innerHTML = html;</textarea>
+document.getElementById("output").innerHTML = html;
+console.log(html);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -636,7 +639,8 @@ <h2>.toLatex(environment?, hrules?)</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">const latex: string = dataFrameStyle(df)
   .setCaption("Results")
-  .toLatex("tabular", true);  // environment, hrules</textarea>
+  .toLatex("tabular", true);  // environment, hrules
+console.log(latex);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -655,7 +659,8 @@ <h2>.exportStyles()</h2>
       <textarea class="playground-editor" spellcheck="false">const records: StyleRecord[] = dataFrameStyle(df)
   .highlightMax()
   .exportStyles();
-// [{ row: 0, col: 1, css: "background-color: yellow;" }, ...]</textarea>
+// [{ row: 0, col: 1, css: "background-color: yellow;" }, ...]
+console.log(records);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -672,7 +677,7 @@ <h2>.clearStyles()</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">// Remove all accumulated styles (keeps caption, hide state, precision)
-styler.clearStyles();</textarea>
+console.log(styler.clearStyles());</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/swaplevel.html b/playground/swaplevel.html
index 54fdad58..c4363906 100644
--- a/playground/swaplevel.html
+++ b/playground/swaplevel.html
@@ -198,7 +198,8 @@ <h2>swapLevelSeries — swap two levels</h2>
 
 const swapped = swapLevelSeries(s, 0, 1);
 // index tuples: [(1,"a"), (2,"a"), (1,"b")]
-// values: [10, 20, 30]</textarea>
+// values: [10, 20, 30]
+console.log(swapped);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -249,7 +250,8 @@ <h2>swapLevelDataFrame — swap row-index levels</h2>
 );
 
 const swapped = swapLevelDataFrame(df, "letter", "number");
-// row index tuples: [(1,"a"), (2,"b")]</textarea>
+// row index tuples: [(1,"a"), (2,"b")]
+console.log(swapped);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -297,7 +299,8 @@ <h2>reorderLevelsSeries — arbitrary level reordering</h2>
 const s = new Series({ data: [10, 20], index: mi as unknown as Index&lt;Label&gt; });
 
 const reordered = reorderLevelsSeries(s, [2, 0, 1]);
-// index tuples: [("x","a",1), ("y","b",2)]</textarea>
+// index tuples: [("x","a",1), ("y","b",2)]
+console.log(reordered);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -348,7 +351,8 @@ <h2>reorderLevelsDataFrame</h2>
 );
 
 const reordered = reorderLevelsDataFrame(df, [1, 0]);
-// row index tuples: [(1,"a"), (2,"b")]</textarea>
+// row index tuples: [(1,"a"), (2,"b")]
+console.log(reordered);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/testing.html b/playground/testing.html
index 49e13fcb..b6a80b37 100644
--- a/playground/testing.html
+++ b/playground/testing.html
@@ -186,7 +186,7 @@ <h2>Passing example</h2>
 
 const a = new Series({ data: [1, 2, 3], name: "x" });
 const b = new Series({ data: [1, 2, 3], name: "x" });
-assertSeriesEqual(a, b);
+console.log(assertSeriesEqual(a, b));
 // ✅ no exception thrown</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -204,7 +204,7 @@ <h2>Failing example</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">const c = new Series({ data: [1, 2, 99], name: "x" });
-assertSeriesEqual(a, c);
+console.log(assertSeriesEqual(a, c));
 // ❌ AssertionError: Series: values differ at index 2 (position 2).
 //    left=3, right=99</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
@@ -224,9 +224,9 @@ <h2>Float tolerance</h2>
       </div>
       <textarea class="playground-editor" spellcheck="false">const p = new Series({ data: [1.0, 2.0] });
 const q = new Series({ data: [1.0 + 1e-9, 2.0] });  // tiny rounding error
-assertSeriesEqual(p, q);                              // ✅ passes (within default atol=1e-8)
+console.log(assertSeriesEqual(p, q));                              // ✅ passes (within default atol=1e-8)
 
-assertSeriesEqual(p, q, { checkExact: true });        // ❌ exact comparison fails</textarea>
+console.log(assertSeriesEqual(p, q, { checkExact: true }));        // ❌ exact comparison fails</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -246,7 +246,7 @@ <h2>Passing example</h2>
 
 const a = DataFrame.fromColumns({ x: [1, 2], y: [3, 4] });
 const b = DataFrame.fromColumns({ x: [1, 2], y: [3, 4] });
-assertFrameEqual(a, b); // ✅</textarea>
+console.log(assertFrameEqual(a, b)); // ✅</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -263,7 +263,7 @@ <h2>Ignore column order</h2>
         </div>
       </div>
       <textarea class="playground-editor" spellcheck="false">const c = DataFrame.fromColumns({ y: [3, 4], x: [1, 2] }); // columns reversed
-assertFrameEqual(a, c, { checkLike: true }); // ✅ order ignored</textarea>
+console.log(assertFrameEqual(a, c, { checkLike: true })); // ✅ order ignored</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -284,10 +284,10 @@ <h2>assertIndexEqual(left, right, options?)</h2>
 
 const a = new Index(["a", "b", "c"]);
 const b = new Index(["a", "b", "c"]);
-assertIndexEqual(a, b); // ✅
+console.log(assertIndexEqual(a, b)); // ✅
 
 const c = new Index(["a", "b", "z"]);
-assertIndexEqual(a, c);
+console.log(assertIndexEqual(a, c));
 // ❌ AssertionError: Index: Index values differ at position 2. left=c, right=z</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
diff --git a/playground/to_datetime.html b/playground/to_datetime.html
index 59e15651..99c08a60 100644
--- a/playground/to_datetime.html
+++ b/playground/to_datetime.html
@@ -164,20 +164,20 @@ <h2>Quick examples</h2>
       <textarea class="playground-editor" spellcheck="false">import { toDatetime, Series } from "tsb";
 
 // Scalar
-toDatetime("2024-03-15");         // Date: Mar 15 2024
-toDatetime(1710460800000);        // Date from Unix ms
-toDatetime(1710460800, { unit: "s" }); // Date from Unix seconds
-toDatetime(null);                 // null
-toDatetime("nope", { errors: "coerce" }); // null
-toDatetime("nope", { errors: "ignore" }); // "nope"
+console.log(toDatetime("2024-03-15"));         // Date: Mar 15 2024
+console.log(toDatetime(1710460800000));        // Date from Unix ms
+console.log(toDatetime(1710460800, { unit: "s" })); // Date from Unix seconds
+console.log(toDatetime(null));                 // null
+console.log(toDatetime("nope", { errors: "coerce" })); // null
+console.log(toDatetime("nope", { errors: "ignore" })); // "nope"
 
 // Array
-toDatetime(["2024-01-01", null, "2024-06-15"]);
+console.log(toDatetime(["2024-01-01", null, "2024-06-15"]));
 // =&gt; [Date, null, Date]
 
 // Series
 const s = new Series({ data: ["2024-01-01", "2024-06-15", null] });
-toDatetime(s);
+console.log(toDatetime(s));
 // =&gt; Series&lt;Date | null&gt; with dtype=datetime</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
diff --git a/playground/to_from_dict.html b/playground/to_from_dict.html
index 890a77e8..c84f9e95 100644
--- a/playground/to_from_dict.html
+++ b/playground/to_from_dict.html
@@ -170,27 +170,27 @@ <h2>Example — all orientations</h2>
 );
 
 // "dict" / "columns"
-toDictOriented(df, "dict");
+console.log(toDictOriented(df, "dict"));
 // { name: { r0: "Alice", r1: "Bob" }, score: { r0: 92, r1: 85 } }
 
 // "list"
-toDictOriented(df, "list");
+console.log(toDictOriented(df, "list"));
 // { name: ["Alice", "Bob"], score: [92, 85] }
 
 // "records"
-toDictOriented(df, "records");
+console.log(toDictOriented(df, "records"));
 // [ { name: "Alice", score: 92 }, { name: "Bob", score: 85 } ]
 
 // "split"
-toDictOriented(df, "split");
+console.log(toDictOriented(df, "split"));
 // { index: ["r0", "r1"], columns: ["name", "score"], data: [["Alice", 92], ["Bob", 85]] }
 
 // "index"
-toDictOriented(df, "index");
+console.log(toDictOriented(df, "index"));
 // { r0: { name: "Alice", score: 92 }, r1: { name: "Bob", score: 85 } }
 
 // fromDictOriented — columns (default)
-fromDictOriented({ name: ["Alice", "Bob"], score: [92, 85] });
+console.log(fromDictOriented({ name: ["Alice", "Bob"], score: [92, 85] }));
 
 // fromDictOriented — index
 fromDictOriented(
diff --git a/playground/to_numeric.html b/playground/to_numeric.html
index 56911d79..cb89d3b3 100644
--- a/playground/to_numeric.html
+++ b/playground/to_numeric.html
@@ -205,7 +205,8 @@ <h2>3 · Series conversion</h2>
   index: ["a", "b", "c"]
 });
 toNumericSeries(prices, { errors: "coerce" })
-// Series [10.5, NaN, 22] name="price"</textarea>
+// Series [10.5, NaN, 22] name="price"
+console.log(prices);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -246,7 +247,8 @@ <h2>5 · Live sandbox</h2>
       <textarea class="playground-editor" spellcheck="false">// Try it yourself!
 const s = new Series(["100", "200.5", "NaN", null, "abc"]);
 const result = toNumericSeries(s, { errors: "coerce" });
-return JSON.stringify(result.values);</textarea>
+return JSON.stringify(result.values);
+console.log(result);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/to_timedelta.html b/playground/to_timedelta.html
index 584edfc5..2287c8eb 100644
--- a/playground/to_timedelta.html
+++ b/playground/to_timedelta.html
@@ -164,34 +164,34 @@ <h2>Quick examples</h2>
       <textarea class="playground-editor" spellcheck="false">import { toTimedelta, Timedelta, formatTimedelta, Series } from "tsb";
 
 // Scalar — various string formats
-toTimedelta("1 days 02:03:04");       // Timedelta(93_784_000 ms)
-toTimedelta("01:30:00");              // Timedelta(5_400_000 ms)
-toTimedelta("P1DT2H3M4S");            // ISO 8601
-toTimedelta("1h 30m 20s 500ms");      // human-readable
+console.log(toTimedelta("1 days 02:03:04"));       // Timedelta(93_784_000 ms)
+console.log(toTimedelta("01:30:00"));              // Timedelta(5_400_000 ms)
+console.log(toTimedelta("P1DT2H3M4S"));            // ISO 8601
+console.log(toTimedelta("1h 30m 20s 500ms"));      // human-readable
 
 // Scalar — numeric
-toTimedelta(1_000_000_000);           // default unit "ns" → 1000 ms
-toTimedelta(5000, { unit: "ms" });    // 5000 ms
-toTimedelta(2, { unit: "D" });        // 2 days
+console.log(toTimedelta(1_000_000_000));           // default unit "ns" → 1000 ms
+console.log(toTimedelta(5000, { unit: "ms" }));    // 5000 ms
+console.log(toTimedelta(2, { unit: "D" }));        // 2 days
 
 // Missing values
-toTimedelta(null);                    // null
-toTimedelta("nope", { errors: "coerce" }); // null
-toTimedelta("nope", { errors: "ignore" }); // "nope" (unchanged)
+console.log(toTimedelta(null));                    // null
+console.log(toTimedelta("nope", { errors: "coerce" })); // null
+console.log(toTimedelta("nope", { errors: "ignore" })); // "nope" (unchanged)
 
 // Timedelta arithmetic
 const a = toTimedelta("1h") as Timedelta;
 const b = toTimedelta("30m") as Timedelta;
-a.add(b).toString();          // "0 days 01:30:00"
-a.subtract(b).totalMs;        // 1_800_000
+console.log(a.add(b).toString());          // "0 days 01:30:00"
+console.log(a.subtract(b).totalMs);        // 1_800_000
 
 // Array
-toTimedelta(["1h", "30m", null]);
+console.log(toTimedelta(["1h", "30m", null]));
 // =&gt; [Timedelta(3_600_000), Timedelta(1_800_000), null]
 
 // Series
 const s = new Series({ data: ["1h", "30m", null] });
-toTimedelta(s);
+console.log(toTimedelta(s));
 // =&gt; Series&lt;Timedelta | null&gt; with dtype=timedelta
 
 // formatTimedelta
diff --git a/playground/transform_agg.html b/playground/transform_agg.html
index 24d1072b..12dc7045 100644
--- a/playground/transform_agg.html
+++ b/playground/transform_agg.html
@@ -167,19 +167,19 @@ <h2>API</h2>
 import { seriesTransform, dataFrameTransform } from "tsb";
 
 // single function or built-in name → Series
-seriesTransform(s, "cumsum");
-seriesTransform(s, (x) =&gt; x);
+console.log(seriesTransform(s, "cumsum"));
+console.log(seriesTransform(s, (x) =&gt; x));
 
 // array → DataFrame (one column per function)
-seriesTransform(s, ["sum", "cumsum", "mean"]);
+console.log(seriesTransform(s, ["sum", "cumsum", "mean"]));
 
 // Record → DataFrame with named columns
-seriesTransform(s, { total: "sum", running: "cumsum" });
+console.log(seriesTransform(s, { total: "sum", running: "cumsum" }));
 
 // DataFrame transform (column-wise by default)
-dataFrameTransform(df, "cumsum");
-dataFrameTransform(df, { a: "sum", b: "cummin" });  // per-column
-dataFrameTransform(df, "cumsum", { axis: 1 });       // row-wise</textarea>
+console.log(dataFrameTransform(df, "cumsum"));
+console.log(dataFrameTransform(df, { a: "sum", b: "cummin" }));  // per-column
+console.log(dataFrameTransform(df, "cumsum", { axis: 1 }));       // row-wise</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -220,20 +220,20 @@ <h2>Examples</h2>
 const s = new Series({ data: [1, 2, 3, 4] });
 
 // cumulative sum
-seriesTransform(s, "cumsum").values;       // [1, 3, 6, 10]
+console.log(seriesTransform(s, "cumsum").values);       // [1, 3, 6, 10]
 
 // broadcast aggregate
-seriesTransform(s, "sum").values;          // [10, 10, 10, 10]
+console.log(seriesTransform(s, "sum").values);          // [10, 10, 10, 10]
 
 // multiple functions
 const df = seriesTransform(s, ["sum", "cumsum", "mean"]);
-df.col("sum").values;    // [10, 10, 10, 10]
-df.col("cumsum").values; // [1, 3, 6, 10]
-df.col("mean").values;   // [2.5, 2.5, 2.5, 2.5]
+console.log(df.col("sum").values);    // [10, 10, 10, 10]
+console.log(df.col("cumsum").values); // [1, 3, 6, 10]
+console.log(df.col("mean").values);   // [2.5, 2.5, 2.5, 2.5]
 
 // DataFrame transform
 const frame = DataFrame.fromColumns({ a: [1,2,3], b: [10,20,30] });
-dataFrameTransform(frame, "cumsum").col("b").values;  // [10, 30, 60]</textarea>
+console.log(dataFrameTransform(frame, "cumsum").col("b").values);  // [10, 30, 60]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/truncate.html b/playground/truncate.html
index 2287cdd8..ca3530d8 100644
--- a/playground/truncate.html
+++ b/playground/truncate.html
@@ -203,9 +203,9 @@ <h2>truncateSeries — keep rows within [before, after]</h2>
 
 const s = new Series({ data: [10, 20, 30, 40, 50], index: [0, 1, 2, 3, 4] });
 
-truncateSeries(s, 1, 3).values;    // [20, 30, 40]
-truncateSeries(s, 2).values;       // [30, 40, 50]
-truncateSeries(s, undefined, 2).values; // [10, 20, 30]</textarea>
+console.log(truncateSeries(s, 1, 3).values);    // [20, 30, 40]
+console.log(truncateSeries(s, 2).values);       // [30, 40, 50]
+console.log(truncateSeries(s, undefined, 2).values); // [10, 20, 30]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -258,8 +258,8 @@ <h2>truncateDataFrame — truncate rows</h2>
 );
 
 const result = truncateDataFrame(df, 1, 3);
-result.col("a").values; // [20, 30, 40]
-result.index.values;    // [1, 2, 3]</textarea>
+console.log(result.col("a").values); // [20, 30, 40]
+console.log(result.index.values);    // [1, 2, 3]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -305,7 +305,7 @@ <h2>truncateDataFrame — truncate columns (axis=1)</h2>
 const df = DataFrame.fromColumns({ a: [1, 2], b: [3, 4], c: [5, 6] });
 
 const result = truncateDataFrame(df, "a", "b", { axis: 1 });
-result.columns.values; // ["a", "b"]</textarea>
+console.log(result.columns.values); // ["a", "b"]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -356,7 +356,7 @@ <h2>String index truncation</h2>
   index: ["apple", "banana", "cherry", "date", "elderberry"],
 });
 
-truncateSeries(s, "banana", "date").values; // [2, 3, 4]</textarea>
+console.log(truncateSeries(s, "banana", "date").values); // [2, 3, 4]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/update.html b/playground/update.html
index 8874d754..ccfa6937 100644
--- a/playground/update.html
+++ b/playground/update.html
@@ -191,7 +191,7 @@ <h2>seriesUpdate — basic overwrite</h2>
 
 const s = new Series({ data: [1, null, 3], index: [0, 1, 2] });
 const other = new Series({ data: [null, 20, null], index: [0, 1, 2] });
-seriesUpdate(s, other).values;
+console.log(seriesUpdate(s, other).values);
 // [1, 20, 3]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -237,7 +237,7 @@ <h2>overwrite=false — only fill NA</h2>
 
 const s = new Series({ data: [1, null, 3] });
 const other = new Series({ data: [10, 20, 30] });
-seriesUpdate(s, other, { overwrite: false }).values;
+console.log(seriesUpdate(s, other, { overwrite: false }).values);
 // [1, 20, 3]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -287,8 +287,8 @@ <h2>dataFrameUpdate — update from another DataFrame</h2>
 const df = DataFrame.fromColumns({ a: [1, null, 3], b: [10, 20, 30] });
 const other = DataFrame.fromColumns({ a: [null, 99, null] });
 const result = dataFrameUpdate(df, other);
-result.col("a").values; // [1, 99, 3]
-result.col("b").values; // [10, 20, 30]</textarea>
+console.log(result.col("a").values); // [1, 99, 3]
+console.log(result.col("b").values); // [10, 20, 30]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -310,7 +310,7 @@ <h2>Label alignment</h2>
 const s = new Series({ data: [1, 2, 3], index: [0, 1, 2] });
 // other only has label 1 — other labels unchanged
 const other = new Series({ data: [99], index: [1] });
-seriesUpdate(s, other).values;
+console.log(seriesUpdate(s, other).values);
 // [1, 99, 3]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
diff --git a/playground/value_counts_full.html b/playground/value_counts_full.html
index 3f285240..11f53c8f 100644
--- a/playground/value_counts_full.html
+++ b/playground/value_counts_full.html
@@ -193,7 +193,8 @@ <h2>Basic binning</h2>
 const s = new Series({ data: [1, 2, 3, 4, 5] });
 const vc = valueCountsBinned(s, 2);
 // Index: ["(0.995, 3.0]", "(3.0, 5.005]"]
-// Values: [3, 2]  ← sorted by count (default)</textarea>
+// Values: [3, 2]  ← sorted by count (default)
+console.log(vc);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -212,7 +213,8 @@ <h2>Interval order (sort=false)</h2>
       <textarea class="playground-editor" spellcheck="false">
 const vc2 = valueCountsBinned(s, 2, { sort: false });
 // Index: ["(0.995, 3.0]", "(3.0, 5.005]"]
-// Values: [3, 2]  ← in interval order</textarea>
+// Values: [3, 2]  ← in interval order
+console.log(vc2);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -231,7 +233,8 @@ <h2>Proportions (normalize=true)</h2>
       <textarea class="playground-editor" spellcheck="false">
 const vc3 = valueCountsBinned(s, 2, { normalize: true });
 // Index: ["(0.995, 3.0]", "(3.0, 5.005]"]
-// Values: [0.6, 0.4]</textarea>
+// Values: [0.6, 0.4]
+console.log(vc3);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -250,7 +253,8 @@ <h2>Handling NaN / null</h2>
       <textarea class="playground-editor" spellcheck="false">
 const s2 = new Series({ data: [1, null, 2, NaN, 3, 4, 5] });
 const vc4 = valueCountsBinned(s2, 2);
-// NaN and null values are excluded.  Total = 5.</textarea>
+// NaN and null values are excluded.  Total = 5.
+console.log(vc4);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/wide_to_long.html b/playground/wide_to_long.html
index 75482237..0f894a49 100644
--- a/playground/wide_to_long.html
+++ b/playground/wide_to_long.html
@@ -192,7 +192,7 @@ <h2>1 · Numeric suffix (default)</h2>
   A1: [1, 2],  A2: [3, 4],
   B1: [5, 6],  B2: [7, 8],
 });
-wideToLong(df, ["A", "B"], "id", "year");
+console.log(wideToLong(df, ["A", "B"], "id", "year"));
 // id  year  A  B
 // x   1     1  5
 // y   1     2  6
@@ -227,7 +227,8 @@ <h2>2 · Underscore separator</h2>
 // 1        pre    80
 // 2        pre    90
 // 1        post   85
-// 2        post   95</textarea>
+// 2        post   95
+console.log(df);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -250,7 +251,7 @@ <h2>3 · Multiple id columns</h2>
   gdp2020: [21, 2.7, 3.8],
   gdp2021: [23, 3.1, 4.2],
 });
-wideToLong(df, "gdp", ["country","region"], "year", { sep: "" });
+console.log(wideToLong(df, "gdp", ["country","region"], "year", { sep: "" }));
 // country  region  year  gdp
 // US       East    2020  21
 // UK       South   2020  2.7
diff --git a/playground/window_extended.html b/playground/window_extended.html
index 0b368ebd..328f97a1 100644
--- a/playground/window_extended.html
+++ b/playground/window_extended.html
@@ -191,7 +191,8 @@ <h2>1. rollingSem — Standard Error of the Mean</h2>
 
 const s = new Series({ data: [2, 4, 4, 4, 5, 5, 7, 9], name: "x" });
 const sem3 = rollingSem(s, 3);
-// [null, null, 0.667, 0, 0.577, 0.577, 1.155, 2.082]</textarea>
+// [null, null, 0.667, 0, 0.577, 0.577, 1.155, 2.082]
+console.log(sem3);</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -232,7 +233,7 @@ <h2>2. rollingSkew — Fisher-Pearson Skewness</h2>
       <textarea class="playground-editor" spellcheck="false">import { rollingSkew, Series } from "tsb";
 
 const s = new Series({ data: [1, 2, 3, 4, 5] });
-rollingSkew(s, 3);
+console.log(rollingSkew(s, 3));
 // [null, null, 0, 0, 0]   ← symmetric windows → zero skew</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -274,7 +275,7 @@ <h2>3. rollingKurt — Excess Kurtosis</h2>
       <textarea class="playground-editor" spellcheck="false">import { rollingKurt, Series } from "tsb";
 
 const s = new Series({ data: [1, 2, 3, 4] });
-rollingKurt(s, 4);
+console.log(rollingKurt(s, 4));
 // [null, null, null, -1.2]   ← uniform distribution has kurt = -1.2</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
@@ -298,9 +299,9 @@ <h2>4. rollingQuantile — Rolling Quantile</h2>
 
 const s = new Series({ data: [1, 2, 3, 4, 5] });
 
-rollingQuantile(s, 0.5, 3);  // rolling median: [null, null, 2, 3, 4]
-rollingQuantile(s, 0.25, 3); // [null, null, 1.5, 2.5, 3.5]
-rollingQuantile(s, 0.75, 3); // [null, null, 2.5, 3.5, 4.5]</textarea>
+console.log(rollingQuantile(s, 0.5, 3));  // rolling median: [null, null, 2, 3, 4]
+console.log(rollingQuantile(s, 0.25, 3)); // [null, null, 1.5, 2.5, 3.5]
+console.log(rollingQuantile(s, 0.75, 3)); // [null, null, 2.5, 3.5, 4.5]</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
diff --git a/playground/xs.html b/playground/xs.html
index 7272d74b..3e838963 100644
--- a/playground/xs.html
+++ b/playground/xs.html
@@ -172,10 +172,10 @@ <h2>Code Examples</h2>
 );
 
 // Select row "y" → Series { a: 2, b: 5 }
-xsDataFrame(df, "y");
+console.log(xsDataFrame(df, "y"));
 
 // Select column "b" → Series { x: 4, y: 5, z: 6 }
-xsDataFrame(df, "b", { axis: 1 });
+console.log(xsDataFrame(df, "b", { axis: 1 }));
 
 // ── MultiIndex ─────────────────────────────────────────────────────────────
 const mi = MultiIndex.fromTuples([
@@ -185,11 +185,11 @@ <h2>Code Examples</h2>
 const miDf = new DataFrame( ... , mi);
 
 // All "A" rows → DataFrame with 2 rows
-xsDataFrame(miDf, "A");
+console.log(xsDataFrame(miDf, "A"));
 
 // ── Series ─────────────────────────────────────────────────────────────────
 const s = new Series({ data: [10, 20, 30], index: ["a", "b", "c"] });
-xsSeries(s, "b"); // → 20</textarea>
+console.log(xsSeries(s, "b")); // → 20</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>