diff --git a/docs/_includes/navbar.html b/docs/_includes/navbar.html
index b13f7e4..4d67a54 100644
--- a/docs/_includes/navbar.html
+++ b/docs/_includes/navbar.html
@@ -17,9 +17,12 @@
     </ul>
 
     <div class="navbar__actions">
-      <button class="theme-toggle" id="themeToggle" aria-label="Toggle dark mode" title="Toggle dark mode">
-        <span class="icon-sun">&#9728;&#65039;</span>
-        <span class="icon-moon">&#127769;</span>
+      <button class="theme-toggle" id="themeToggle" aria-label="Toggle dark mode" title="Toggle dark mode" role="switch" aria-checked="false">
+        <span class="theme-toggle__track">
+          <span class="theme-toggle__icon theme-toggle__icon--sun">&#9728;&#65039;</span>
+          <span class="theme-toggle__icon theme-toggle__icon--moon">&#127769;</span>
+          <span class="theme-toggle__thumb"></span>
+        </span>
       </button>
 
       <a href="https://github.com/thanglequoc/timer-ninja" target="_blank" rel="noopener" class="navbar__github" aria-label="GitHub">
diff --git a/docs/_sass/_navbar.scss b/docs/_sass/_navbar.scss
index 6944d8e..b6a6d44 100644
--- a/docs/_sass/_navbar.scss
+++ b/docs/_sass/_navbar.scss
@@ -110,38 +110,81 @@
   gap: $space-md;
 }
 
-// Theme toggle
+// Theme toggle slider
 .theme-toggle {
   background: none;
-  border: 2px solid var(--color-border);
-  border-radius: 50%;
-  width: 38px;
-  height: 38px;
+  border: none;
+  padding: 0;
+  cursor: pointer;
+  line-height: 1;
   display: flex;
   align-items: center;
-  justify-content: center;
-  cursor: pointer;
-  color: var(--color-text-muted);
-  transition: all $transition-normal;
-  font-size: 1.1rem;
+}
 
-  &:hover {
-    border-color: var(--color-primary);
-    color: var(--color-primary);
-    transform: rotate(20deg);
+.theme-toggle__track {
+  position: relative;
+  width: 56px;
+  height: 28px;
+  background: #d1e9eb;
+  border-radius: 999px;
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  padding: 0 6px;
+  transition: background-color 0.3s ease;
+  box-shadow: inset 0 1px 3px rgba(0, 0, 0, 0.1);
+}
+
+.theme-toggle__icon {
+  font-size: 0.85rem;
+  line-height: 1;
+  z-index: 1;
+  transition: opacity 0.3s ease;
+  user-select: none;
+}
+
+.theme-toggle__icon--sun {
+  opacity: 1;
+}
+
+.theme-toggle__icon--moon {
+  opacity: 0.4;
+}
+
+.theme-toggle__thumb {
+  position: absolute;
+  top: 3px;
+  left: 3px;
+  width: 22px;
+  height: 22px;
+  background: #fff;
+  border-radius: 50%;
+  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.2);
+  transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
+}
+
+.theme-toggle:hover .theme-toggle__thumb {
+  box-shadow: 0 2px 8px rgba(70, 191, 198, 0.4);
+}
+
+[data-theme="dark"] {
+  .theme-toggle__track {
+    background: #2a3a4a;
   }
 
-  .icon-sun,
-  .icon-moon {
-    transition: opacity $transition-fast, transform $transition-normal;
+  .theme-toggle__icon--sun {
+    opacity: 0.4;
   }
 
-  .icon-moon { display: none; }
-}
+  .theme-toggle__icon--moon {
+    opacity: 1;
+  }
 
-[data-theme="dark"] .theme-toggle {
-  .icon-sun { display: none; }
-  .icon-moon { display: block; }
+  .theme-toggle__thumb {
+    transform: translateX(28px);
+    background: #1a2636;
+    box-shadow: 0 1px 4px rgba(0, 0, 0, 0.4), inset 0 0 0 1px rgba(109, 213, 219, 0.3);
+  }
 }
 
 // GitHub link
diff --git a/docs/assets/js/theme-toggle.js b/docs/assets/js/theme-toggle.js
index ce67651..5f233ef 100644
--- a/docs/assets/js/theme-toggle.js
+++ b/docs/assets/js/theme-toggle.js
@@ -19,6 +19,9 @@
   function setTheme(theme) {
     html.setAttribute('data-theme', theme);
     localStorage.setItem(STORAGE_KEY, theme);
+    if (toggle) {
+      toggle.setAttribute('aria-checked', theme === 'dark' ? 'true' : 'false');
+    }
   }
 
   // Initialize