Update index.html

index.html

@@ -315,7 +315,16 @@ footer {
   </label>
 </div>
 
-
+<script>
+  document.getElementById('theme-switch').addEventListener('change', function() {
+    var dot = document.querySelector('.dot');
+    if (this.checked) {
+      dot.style.transform = 'translateX(24px)';
+    } else {
+      dot.style.transform = 'translateX(0)';
+    }
+  });
+</script>
 
         <div class="main">
             <h2>Introduction</h2>