diff --git a/src/lib/map.js b/src/lib/map.js
index fefc9fd..f9c918b 100644
--- a/src/lib/map.js
+++ b/src/lib/map.js
@@ -8,6 +8,7 @@ import utils from "./utils.js"
  *
  * Each option can be declared as a function. The function is passed the
  * original datum and indices that correspond to how deeply the datum is nested.
+ * For example, bar chart data may be nested up to three levels
  *
  * However, it's often useful to use a shorthand syntax instead. If the
  * property is an array, the array item at the index corresponding to the
@@ -102,26 +103,31 @@ const recur = (map, data, depth, indices = []) => {
 /**
  * @private
  * @param {MapOptions} options
- * @param {any[]} data
+ * @param {any[]} data - Flattened data
  * @param {Object} [overrides]
- * @param {number} [overrides.minValue]
- * @param {boolean} [overrides.sum]
- * @param {number} [overrides.maxDepth]
+ * @param {number} [overrides.minValue] - Minimum value required in order to
+ * render a label, as a percentage of the whole between zero and one.
+ * @param {number} [overrides.maxDepth] - Stop recurring through values early
+ * when, for example, the deepest array represents different data, like the
+ * scatter plot.
+ * @param {number} [overrides.colors] - The total number of colors from which to
+ * generate a new mapped color.
  * @returns {Function} converter
  */
 const Map = function (
   options,
   data = [],
-  { minValue = 0, sum = false, maxDepth } = {}
+  { minValue = 0, maxDepth, colors = data.length } = {}
 ) {
   const map = Object.assign({}, defaults, options)
 
-  const values = data.map((v) => (Array.isArray(v) ? v : [v]).map(map.value))
-  const places = Math.min(
-    Math.max(...values.flat().map(utils.decimalPlaces)),
-    2
-  )
+  // Unless the data makes sense to be multi-dimensional, issue a warning
+  if (data.length > 0 && Array.isArray(map.y ? map.y(data[0]) : data[0])) {
+    console.warn("Data should be flattened when constructing a Map")
+  }
 
+  const values = data.map(map.y || map.value)
+  const places = Math.min(Math.max(...values.map(utils.decimalPlaces)), 2)
 
   // By default, a label will only show when it exceeds the minimum value
   // specified by a chart. It uses the largest number of decimal places found
@@ -164,7 +170,7 @@ const Map = function (
   // A color function can return a background color, or an array of background
   // and foreground colors. This wrapper ensures an array is always returned by
   // the color function.
-  const base = map.color || ((v, i) => getColor(i / (data.length - 1)))
+  const base = map.color || ((v, i) => getColor(i / (colors - 1)))
   map.color = wrapColor(base)
 
   // The return function contains references to each mapping function in cases
diff --git a/src/templates/bar.js b/src/templates/bar.js
index 3db901c..8c90480 100644
--- a/src/templates/bar.js
+++ b/src/templates/bar.js
@@ -60,9 +60,9 @@ import wrap from "./wrap.js"
  *      [34.44, 14.79, 30.64, 18.31, 1.82],
  *   ],
  *   map: {
- *     width: (v, i) => v === 30.64 ? 0.8 : 0.6,
- *     label: (v, i) => v === 30.64 ? v.toFixed(1) : false,
- *     key: (v, i) => ["A", "B", "C", "D", "E"][i],
+ *     width: (v) => v === 30.64 ? 0.8 : 0.6,
+ *     label: (v) => v === 30.64 ? v.toFixed(1) : false,
+ *     key: ["A", "B", "C", "D", "E"],
  *   },
  *   stack: true,
  *   xAxis: { label: ["I", "II", "III"] }
@@ -85,8 +85,9 @@ import wrap from "./wrap.js"
  *   map: {
  *     key: ["In", "Out"],
  *     series: ["A", "B", "C"],
- *     tally: Math.round,
- *     label: Math.round,
+ *     value: Math.round,
+ *     tally: true,
+ *     label: true,
  *     attrs: (d) => ({ "data-value": d })
  *   },
  *   xAxis: { label: ["I", "II"] }
@@ -102,8 +103,10 @@ export default ({
   xAxis,
   yAxis,
 }) => {
+  // If the data is only one-level deep, it needs an initial wrapper
   data = data.map((v) => (Array.isArray(v) ? v : [v]))
 
+  // If the data is only two-levels deep, wrap based on the `stack` option
   if (data.length && !Array.isArray(data[0][0])) {
     data = stack ? data.map((d) => [d]) : data.map((d) => d.map((d) => [d]))
   } else {
@@ -122,27 +125,43 @@ export default ({
     }
   }
 
-  if (map && map.series && Array.isArray(map.key)) {
+  // Being triple-nested, bar charts need help to make an intuitive choice about
+  // which index to use when picking an item from an array.
+  if (Array.isArray(map?.key)) {
     const arr = map.key
-    map.key = (v, i, j) => arr[j]
+    map.key = (v, k, j, i) => arr[maxStack > 1 ? i : j]
+  }
+
+  if (Array.isArray(map?.series)) {
+    const arr = map.series
+    map.series = (v, k, j) => arr[j]
+  }
+
+  if (Array.isArray(map?.color)) {
+    const arr = map.color
+    map.color = (v, k, j, i) => arr[maxStack > 1 ? i : j]
   }
 
   map = new Map(
     {
-      color: (v, i, j) =>
-        getColor(maxStack === 1 ? i / (maxSeries - 1) : j / (maxStack - 1)),
+      // Other charts use the shallow index, but bar charts select a color
+      // from the deepest index, or second deepest if unstacked.
+      color: (v, k, j, i) => {
+        return getColor(
+          maxStack === 1 ? j / (maxSeries - 1) : i / (maxStack - 1)
+        )
+      },
       width: 0.6,
       ...map,
     },
-    data.flat(),
-    { sum: stack, minValue: 0.05 }
+    stack ? data.flat().map((d) => utils.sum(d)) : data.flat(2),
+    { minValue: 0.05 }
   )
 
-  data = data.map(map)
+  data = map(data)
 
   const maxWidth = Math.max(...data.flat(2).map((d) => d.width))
-
-  const values = data.flat().map(utils.sum)
+  const values = data.flat().map((d) => utils.sum(d))
 
   xAxis = {
     ticks: data.length,
diff --git a/src/templates/line.js b/src/templates/line.js
index aa0210e..e5eb3dd 100644
--- a/src/templates/line.js
+++ b/src/templates/line.js
@@ -165,8 +165,8 @@ export default ({
       y: (d) => d,
       ...map,
     },
-    data,
-    { minValue: -Infinity }
+    data.flat(),
+    { minValue: -Infinity, colors: data.length }
   )
 
   data = map(data)
diff --git a/src/templates/scatter.js b/src/templates/scatter.js
index d9b182b..2bfe02c 100644
--- a/src/templates/scatter.js
+++ b/src/templates/scatter.js
@@ -70,8 +70,8 @@ export default ({ data, title, description, map, xAxis, yAxis }) => {
       r: 1,
       ...map,
     },
-    data,
-    { minValue: -Infinity, maxDepth: 2 }
+    data.flat(),
+    { minValue: -Infinity, maxDepth: 2, colors: data.length }
   )
 
   data = map(data)
diff --git a/test/lib/map.test.js b/test/lib/map.test.js
index 5056640..220e20d 100644
--- a/test/lib/map.test.js
+++ b/test/lib/map.test.js
@@ -1,4 +1,7 @@
+import { jest } from "@jest/globals"
+
 import map from "../../src/lib/map.js"
+import utils from "../../src/lib/utils.js"
 
 describe("map", () => {
   test("to return a converter function", () => {
@@ -9,13 +12,15 @@ describe("map", () => {
     const m = { label: (v) => v + "" }
     const d = [[[1]]]
     const o = { minValue: 0 }
-    expect(map(m, d, o)(d)).toStrictEqual([
+
+    expect(map(m, d.flat(2), o)(d)).toStrictEqual([
       [[{ color: ["#0036b0", "#fff"], label: "1", tally: false, value: 1 }]],
     ])
   })
 
   test("to wrap non-functions", () => {
     const d = [1]
+
     expect(map({ a: [0], b: 0, c: "0" }, d)(d)).toStrictEqual([
       {
         a: 0,
@@ -31,8 +36,15 @@ describe("map", () => {
 
   test("to sum and respect `minValue`", () => {
     const d = [[1, 2]]
-    const o = { sum: true, minValue: 0.34 }
-    expect(map({}, d, o)(d)).toStrictEqual([
+    const o = { minValue: 0.34 }
+
+    expect(
+      map(
+        {},
+        d.map((d) => utils.sum(d)),
+        o
+      )(d)
+    ).toStrictEqual([
       [
         {
           color: ["#0036b0", "#fff"],
@@ -49,4 +61,13 @@ describe("map", () => {
       ],
     ])
   })
+
+  test("warns about nested data", () => {
+    const d = [[]]
+
+    console.warn = jest.fn()
+    map({}, d)(d)
+
+    expect(console.warn).toHaveBeenCalled()
+  })
 })
diff --git a/test/templates/bar.test.js b/test/templates/bar.test.js
index 295b34c..652e622 100644
--- a/test/templates/bar.test.js
+++ b/test/templates/bar.test.js
@@ -1,24 +1,39 @@
 import bar from "../../src/templates/bar.js"
 
+const simple = [1, 2, 3]
+const nested = [[[1, 2]], [[3, 4]], [[5, 6]], [[7, 8]]]
+
 describe("bar", () => {
   test("is a function", () => {
     expect(typeof bar).toBe("function")
   })
 
   test("renders basic chart", () => {
-    expect(bar({ data: [1, 2, 3] })).toMatch(
+    expect(bar({ data: simple })).toMatch(
       '<div class="shown"><div class="chart chart-bar'
     )
   })
 
   test("renders a single datum", () => {
-    expect(bar({ data: [1] })).not.toMatch('width="0"')
+    expect(bar({ data: simple.slice(0, 1) })).not.toMatch('width="0"')
+  })
+
+  test("renders correct classes", () => {
+    const result = bar({
+      data: nested,
+      map: { series: [1, 2] },
+      xAxis: { label: (d, j, i) => j },
+    })
+
+    expect(result).toMatch("has-series")
+    expect(result).toMatch("has-xaxis")
+    expect(result).toMatch("has-yaxis")
   })
 
   test("renders custom keys", () => {
     expect(
       bar({
-        data: [[[1, 2]], [[3, 4]]],
+        data: nested,
         map: {
           series: ["s1", "s2"],
           key: ["custom1", "custom2"],
diff --git a/types/types.d.ts b/types/types.d.ts
index c2d8caf..3de9783 100644
--- a/types/types.d.ts
+++ b/types/types.d.ts
@@ -31,9 +31,9 @@ declare module "shown" {
      *      [34.44, 14.79, 30.64, 18.31, 1.82],
      *   ],
      *   map: {
-     *     width: (v, i) => v === 30.64 ? 0.8 : 0.6,
-     *     label: (v, i) => v === 30.64 ? v.toFixed(1) : false,
-     *     key: (v, i) => ["A", "B", "C", "D", "E"][i],
+     *     width: (v) => v === 30.64 ? 0.8 : 0.6,
+     *     label: (v) => v === 30.64 ? v.toFixed(1) : false,
+     *     key: ["A", "B", "C", "D", "E"],
      *   },
      *   stack: true,
      *   xAxis: { label: ["I", "II", "III"] }
@@ -55,8 +55,9 @@ declare module "shown" {
      *   map: {
      *     key: ["In", "Out"],
      *     series: ["A", "B", "C"],
-     *     tally: Math.round,
-     *     label: Math.round,
+     *     value: Math.round,
+     *     tally: true,
+     *     label: true,
      *     attrs: (d) => ({ "data-value": d })
      *   },
      *   xAxis: { label: ["I", "II"] }
@@ -292,6 +293,7 @@ declare module "shown" {
  *
  * Each option can be declared as a function. The function is passed the
  * original datum and indices that correspond to how deeply the datum is nested.
+ * For example, bar chart data may be nested up to three levels
  *
  * However, it's often useful to use a shorthand syntax instead. If the
  * property is an array, the array item at the index corresponding to the