404 page

src/App.tsx

@@ -11,6 +11,7 @@ import TracyPage from './pages/TracyPage'
 import SystemsPage from './pages/SystemsPage'
 import ResilienceGamePage from './pages/ResilienceGamePage'
 import MetricsPage from './pages/MetricsPage'
+import NotFoundPage from './pages/NotFoundPage'
 
 function App() {
   return (
@@ -29,6 +30,7 @@ function App() {
       <Route path="/resilience/phase1/level1" element={<ResilienceGamePage />} />
       <Route path="/top" element={<Navigate to="/top/sets" replace />} />
       <Route path="/top/:module" element={<LearningPage />} />
+      <Route path="*" element={<NotFoundPage />} />
     </Routes>
   )
 }

src/pages/NotFoundPage.module.css

@@ -0,0 +1,92 @@
+.notFoundPage {
+  position: relative;
+  min-height: 100vh;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  overflow: hidden;
+}
+
+.content {
+  position: relative;
+  z-index: 2;
+  text-align: center;
+  padding: 2rem;
+}
+
+.errorContainer {
+  background: rgba(0, 0, 0, 0.8);
+  backdrop-filter: blur(10px);
+  border-radius: 16px;
+  padding: 3rem 2rem;
+  border: 1px solid rgba(255, 255, 255, 0.1);
+  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
+  max-width: 500px;
+  margin: 0 auto;
+}
+
+.errorCode {
+  font-size: 6rem;
+  font-weight: bold;
+  margin: 0;
+  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
+  -webkit-background-clip: text;
+  background-clip: text;
+  -webkit-text-fill-color: transparent;
+  line-height: 1;
+  margin-bottom: 1rem;
+}
+
+.errorMessage {
+  font-size: 2rem;
+  margin: 0 0 1rem 0;
+  color: #ffffff;
+  font-weight: 600;
+}
+
+.errorDescription {
+  font-size: 1.1rem;
+  color: #cccccc;
+  margin-bottom: 2.5rem;
+  line-height: 1.5;
+}
+
+.homeButton {
+  display: inline-block;
+  padding: 12px 32px;
+  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
+  color: white;
+  text-decoration: none;
+  border-radius: 25px;
+  font-weight: 600;
+  font-size: 1rem;
+  transition: all 0.3s ease;
+  border: none;
+  cursor: pointer;
+  box-shadow: 0 4px 15px rgba(102, 126, 234, 0.4);
+}
+
+.homeButton:hover {
+  transform: translateY(-2px);
+  box-shadow: 0 6px 20px rgba(102, 126, 234, 0.6);
+  filter: brightness(1.1);
+}
+
+.homeButton:active {
+  transform: translateY(0);
+}
+
+@media (max-width: 768px) {
+  .errorCode {
+    font-size: 4rem;
+  }
+
+  .errorMessage {
+    font-size: 1.5rem;
+  }
+
+  .errorContainer {
+    padding: 2rem 1.5rem;
+    margin: 1rem;
+  }
+}

src/pages/NotFoundPage.tsx

@@ -0,0 +1,25 @@
+import { Link } from 'react-router-dom'
+import JuliaSetBackground from '@/components/JuliaSetBackground'
+import styles from './NotFoundPage.module.css'
+
+const NotFoundPage = () => {
+  return (
+    <div className={styles.notFoundPage}>
+      <JuliaSetBackground />
+      <main className={styles.content}>
+        <div className={styles.errorContainer}>
+          <h1 className={styles.errorCode}>404</h1>
+          <h2 className={styles.errorMessage}>Page Not Found</h2>
+          <p className={styles.errorDescription}>
+            The page you're looking for doesn't exist or has been moved.
+          </p>
+          <Link to="/" className={styles.homeButton}>
+            Return Home
+          </Link>
+        </div>
+      </main>
+    </div>
+  )
+}
+
+export default NotFoundPage