diff --git a/requirements.txt b/requirements.txt
index 97dc7cd..f4ca909 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,2 +1,5 @@
 fastapi
 uvicorn
+pytest
+requests
+httpx
diff --git a/src/app.py b/src/app.py
index 4ebb1d9..5bd14ce 100644
--- a/src/app.py
+++ b/src/app.py
@@ -38,6 +38,42 @@
         "schedule": "Mondays, Wednesdays, Fridays, 2:00 PM - 3:00 PM",
         "max_participants": 30,
         "participants": ["john@mergington.edu", "olivia@mergington.edu"]
+    },
+    "Basketball Team": {
+        "description": "Competitive basketball team for intramural and regional tournaments",
+        "schedule": "Mondays and Thursdays, 4:00 PM - 5:30 PM",
+        "max_participants": 15,
+        "participants": ["james@mergington.edu"]
+    },
+    "Tennis Club": {
+        "description": "Learn tennis skills and participate in friendly matches",
+        "schedule": "Wednesdays and Saturdays, 3:00 PM - 4:30 PM",
+        "max_participants": 16,
+        "participants": ["alex@mergington.edu", "sarah@mergington.edu"]
+    },
+    "Art Studio": {
+        "description": "Explore painting, drawing, and other visual arts",
+        "schedule": "Tuesdays and Fridays, 3:30 PM - 5:00 PM",
+        "max_participants": 18,
+        "participants": ["grace@mergington.edu"]
+    },
+    "Music Band": {
+        "description": "Join our school band and perform at events",
+        "schedule": "Mondays, Wednesdays, Fridays, 3:30 PM - 4:30 PM",
+        "max_participants": 25,
+        "participants": ["lucas@mergington.edu", "sophia@mergington.edu"]
+    },
+    "Debate Society": {
+        "description": "Develop public speaking and critical thinking skills",
+        "schedule": "Thursdays, 3:30 PM - 5:00 PM",
+        "max_participants": 20,
+        "participants": ["charlotte@mergington.edu", "henry@mergington.edu"]
+    },
+    "Science Club": {
+        "description": "Conduct experiments and explore STEM concepts",
+        "schedule": "Wednesdays, 3:30 PM - 4:30 PM",
+        "max_participants": 22,
+        "participants": ["noah@mergington.edu"]
     }
 }
 
@@ -62,6 +98,32 @@ def signup_for_activity(activity_name: str, email: str):
     # Get the specific activity
     activity = activities[activity_name]
 
+    # Validate student is not already signed up
+    if email in activity["participants"]:
+        raise HTTPException(status_code=400, detail="Student already signed up for this activity")
+
     # Add student
     activity["participants"].append(email)
-    return {"message": f"Signed up {email} for {activity_name}"}
+    return {"message": f"Signed up {email} for {activity_name}", "participants": activity["participants"]}
+
+
+@app.delete("/activities/{activity_name}/participants")
+def unregister_participant(activity_name: str, email: str):
+    """Unregister a student from an activity
+
+    Calls should pass the student email as a query parameter, e.g.
+    DELETE /activities/Chess%20Club/participants?email=student@example.com
+    """
+    # Validate activity exists
+    if activity_name not in activities:
+        raise HTTPException(status_code=404, detail="Activity not found")
+
+    activity = activities[activity_name]
+
+    # Validate student is currently signed up
+    if email not in activity.get("participants", []):
+        raise HTTPException(status_code=404, detail="Student not signed up for this activity")
+
+    # Remove the student
+    activity["participants"].remove(email)
+    return {"message": f"Unregistered {email} from {activity_name}", "participants": activity["participants"]}
diff --git a/src/static/app.js b/src/static/app.js
index dcc1e38..0378ed1 100644
--- a/src/static/app.js
+++ b/src/static/app.js
@@ -4,29 +4,117 @@ document.addEventListener("DOMContentLoaded", () => {
   const signupForm = document.getElementById("signup-form");
   const messageDiv = document.getElementById("message");
 
+  // Function to safely set text
+  function setText(node, text) { node.textContent = text || ""; }
+
   // Function to fetch activities from API
   async function fetchActivities() {
     try {
-      const response = await fetch("/activities");
+      const response = await fetch("/activities", { cache: "no-store" });
       const activities = await response.json();
 
-      // Clear loading message
+      // Clear loading message / list
       activitiesList.innerHTML = "";
 
+      // Reset dropdown (keep placeholder)
+      while (activitySelect.options.length > 1) activitySelect.remove(1);
+
       // Populate activities list
       Object.entries(activities).forEach(([name, details]) => {
         const activityCard = document.createElement("div");
         activityCard.className = "activity-card";
 
-        const spotsLeft = details.max_participants - details.participants.length;
+        // Header
+        const title = document.createElement("h4");
+        setText(title, name);
+        activityCard.appendChild(title);
+
+        // Description
+        const desc = document.createElement("p");
+        setText(desc, details.description);
+        activityCard.appendChild(desc);
+
+        // Schedule
+        const sched = document.createElement("p");
+        sched.innerHTML = `<strong>Schedule:</strong> ${details.schedule || ""}`;
+        activityCard.appendChild(sched);
+
+        // Availability
+        const spotsLeft = Math.max(0, (details.max_participants || 0) - (details.participants?.length || 0));
+        const avail = document.createElement("p");
+        avail.innerHTML = `<strong>Availability:</strong> ${spotsLeft} spots left`;
+        activityCard.appendChild(avail);
+
+        // Participants section
+        const participantsSection = document.createElement("div");
+        participantsSection.className = "participants-section";
+
+        const participantsHeader = document.createElement("h5");
+        participantsHeader.innerHTML = `Participants <span class="badge">${(details.participants || []).length}</span>`;
+        participantsSection.appendChild(participantsHeader);
+
+        if (details.participants && details.participants.length) {
+          const ul = document.createElement("ul");
+          ul.className = "participant-list";
+          details.participants.forEach(p => {
+            const li = document.createElement("li");
+            li.className = "participant-item";
 
-        activityCard.innerHTML = `
-          <h4>${name}</h4>
-          <p>${details.description}</p>
-          <p><strong>Schedule:</strong> ${details.schedule}</p>
-          <p><strong>Availability:</strong> ${spotsLeft} spots left</p>
-        `;
+            // name/email text
+            const span = document.createElement("span");
+            setText(span, p);
+
+            // delete / unregister button
+            const btn = document.createElement("button");
+            btn.className = "delete-btn";
+            btn.title = `Unregister ${p}`;
+            btn.setAttribute("aria-label", `Unregister ${p} from ${name}`);
+            btn.innerHTML = `<span class="delete-icon">✖</span>`;
+
+            // call API to unregister when clicked
+            btn.addEventListener("click", async () => {
+              const ok = window.confirm(`Remove ${p} from ${name}?`);
+              if (!ok) return;
+
+              try {
+                const resp = await fetch(`/activities/${encodeURIComponent(name)}/participants?email=${encodeURIComponent(p)}`, { method: "DELETE", cache: "no-store" });
+                const resBody = await resp.json();
+
+                if (resp.ok) {
+                  messageDiv.textContent = resBody.message || 'Removed participant';
+                  messageDiv.className = 'message success';
+                } else {
+                  messageDiv.textContent = resBody.detail || 'Failed to remove participant';
+                  messageDiv.className = 'message error';
+                }
+                messageDiv.classList.remove('hidden');
+
+                // Refresh activities list
+                await fetchActivities();
+
+                setTimeout(() => messageDiv.classList.add('hidden'), 4000);
+              } catch (err) {
+                console.error('Error unregistering participant:', err);
+                messageDiv.textContent = 'Failed to remove participant — please try again.';
+                messageDiv.className = 'message error';
+                messageDiv.classList.remove('hidden');
+                setTimeout(() => messageDiv.classList.add('hidden'), 4000);
+              }
+            });
+
+            li.appendChild(span);
+            li.appendChild(btn);
+            ul.appendChild(li);
+          });
+          participantsSection.appendChild(ul);
+        } else {
+          const none = document.createElement("p");
+          none.className = "no-participants";
+          setText(none, "No participants yet.");
+          participantsSection.appendChild(none);
+        }
 
+        activityCard.appendChild(participantsSection);
         activitiesList.appendChild(activityCard);
 
         // Add option to select dropdown
@@ -45,7 +133,7 @@ document.addEventListener("DOMContentLoaded", () => {
   signupForm.addEventListener("submit", async (event) => {
     event.preventDefault();
 
-    const email = document.getElementById("email").value;
+    const email = document.getElementById("email").value.trim();
     const activity = document.getElementById("activity").value;
 
     try {
@@ -53,6 +141,7 @@ document.addEventListener("DOMContentLoaded", () => {
         `/activities/${encodeURIComponent(activity)}/signup?email=${encodeURIComponent(email)}`,
         {
           method: "POST",
+          cache: "no-store",
         }
       );
 
@@ -60,11 +149,12 @@ document.addEventListener("DOMContentLoaded", () => {
 
       if (response.ok) {
         messageDiv.textContent = result.message;
-        messageDiv.className = "success";
+        messageDiv.className = "message success";
         signupForm.reset();
+        await fetchActivities(); // refresh participants immediately
       } else {
         messageDiv.textContent = result.detail || "An error occurred";
-        messageDiv.className = "error";
+        messageDiv.className = "message error";
       }
 
       messageDiv.classList.remove("hidden");
@@ -75,7 +165,7 @@ document.addEventListener("DOMContentLoaded", () => {
       }, 5000);
     } catch (error) {
       messageDiv.textContent = "Failed to sign up. Please try again.";
-      messageDiv.className = "error";
+      messageDiv.className = "message error";
       messageDiv.classList.remove("hidden");
       console.error("Error signing up:", error);
     }
diff --git a/src/static/styles.css b/src/static/styles.css
index a533b32..f0fb71d 100644
--- a/src/static/styles.css
+++ b/src/static/styles.css
@@ -142,3 +142,83 @@ footer {
   padding: 20px;
   color: #666;
 }
+
+.participants-section {
+  margin-top: 12px;
+  padding-top: 10px;
+  border-top: 1px dashed rgba(26, 35, 126, 0.08);
+}
+
+.participants-section h5 {
+  margin: 0 0 8px 0;
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  font-size: 14px;
+  color: #2b2b2b;
+  font-weight: 600;
+}
+
+.participants-section .badge {
+  background: linear-gradient(180deg,#ffffff,#eef4ff);
+  border: 1px solid #dbe6ff;
+  color: #1a237e;
+  font-weight: 700;
+  padding: 2px 8px;
+  border-radius: 999px;
+  font-size: 12px;
+  box-shadow: inset 0 -1px 0 rgba(0,0,0,0.03);
+}
+
+.participant-list {
+  list-style: none; /* hide default bullets */
+  padding-left: 0;
+  margin: 6px 0 0 0;
+}
+
+.participant-item {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  padding: 8px 10px;
+  margin-bottom: 8px;
+  border-radius: 8px;
+  background: linear-gradient(180deg,#fbfbff,#ffffff);
+  border: 1px solid #f0f0f5;
+  font-size: 14px;
+  color: #333;
+  transition: transform .08s ease, box-shadow .12s ease;
+}
+
+.participant-item:hover {
+  transform: translateY(-2px);
+  box-shadow: 0 6px 12px rgba(24, 39, 128, 0.06);
+}
+
+.delete-btn {
+  background: transparent;
+  border: none;
+  color: #d32f2f;
+  font-weight: 700;
+  cursor: pointer;
+  padding: 4px 6px;
+  border-radius: 6px;
+  display: inline-flex;
+  align-items: center;
+  gap: 6px;
+}
+
+.delete-btn:hover {
+  background: rgba(211, 47, 47, 0.08);
+}
+
+.delete-icon {
+  font-size: 14px;
+  line-height: 1;
+}
+
+.no-participants {
+  font-size: 13px;
+  color: #777;
+  margin: 6px 0 0 0;
+}
diff --git a/tests/test_app.py b/tests/test_app.py
new file mode 100644
index 0000000..85e4a65
--- /dev/null
+++ b/tests/test_app.py
@@ -0,0 +1,53 @@
+from fastapi.testclient import TestClient
+from src.app import app, activities
+
+
+client = TestClient(app)
+
+
+def test_get_activities():
+    resp = client.get("/activities")
+    assert resp.status_code == 200
+    data = resp.json()
+    # Expect to get the same keys as the in-memory activities mapping
+    assert set(data.keys()) == set(activities.keys())
+
+
+def test_signup_and_unregister_flow():
+    activity_name = "Chess Club"
+    email = "test_student@example.com"
+
+    # Ensure email is not already registered (cleanup if necessary)
+    if email in activities[activity_name]["participants"]:
+        activities[activity_name]["participants"].remove(email)
+
+    # Sign up
+    resp = client.post(f"/activities/{activity_name}/signup?email={email}")
+    assert resp.status_code == 200
+    body = resp.json()
+    assert "Signed up" in body.get("message", "")
+    # participants should include newly added email
+    assert email in body.get("participants", [])
+
+    # Attempt duplicate signup should return 400
+    dup = client.post(f"/activities/{activity_name}/signup?email={email}")
+    assert dup.status_code == 400
+
+    # Now unregister
+    rem = client.delete(f"/activities/{activity_name}/participants?email={email}")
+    assert rem.status_code == 200
+    rbody = rem.json()
+    assert "Unregistered" in rbody.get("message", "")
+    assert email not in rbody.get("participants", [])
+
+
+def test_unregister_not_found():
+    activity_name = "Chess Club"
+    email = "not_registered@example.com"
+
+    # Make sure this email is not present
+    if email in activities[activity_name]["participants"]:
+        activities[activity_name]["participants"].remove(email)
+
+    resp = client.delete(f"/activities/{activity_name}/participants?email={email}")
+    assert resp.status_code == 404
\ No newline at end of file