diff --git a/assets/site.css b/assets/site.css
index fc60032..3a5fb19 100644
--- a/assets/site.css
+++ b/assets/site.css
@@ -65,6 +65,42 @@ main {
   padding: 1.5rem;
 }
 
+section {
+  margin-bottom: 1.5rem;
+}
+
+.category-toggle {
+  background: none;
+  border: none;
+  color: var(--primary-color);
+  font-size: 1rem;
+  cursor: pointer;
+  padding: 0;
+  margin-right: 0.5rem;
+  vertical-align: middle;
+  transition: transform 0.2s ease;
+}
+
+.category-toggle:hover {
+  opacity: 0.7;
+}
+
+.category-toggle[aria-expanded="false"] {
+  transform: rotate(-90deg);
+}
+
+.category-content {
+  overflow: hidden;
+  transition: max-height 0.3s ease, opacity 0.3s ease;
+  opacity: 1;
+  max-height: 1000px;
+}
+
+.category-content.collapsed {
+  max-height: 0;
+  opacity: 0;
+}
+
 #posts-status {
   font-style: italic;
 }
diff --git a/index.html b/index.html
index 9749e1e..be38bbd 100644
--- a/index.html
+++ b/index.html
@@ -26,163 +26,196 @@
     <h1>Learn sleep repeat</h1>
 
     <section>
+      <button class="category-toggle" aria-expanded="true">▼</button>
       <h2>Creative Arts & Culture</h2>
-
-      <h3>Music</h3>
-      <ul>
-        <li><a href="/2024/11/05/music-theory.html">Music Theory</a></li>
-        <li><a href="/2024/07/12/ukulele.html">Ukulele</a></li>
-        <li><a href="/2024/07/12/ukulele-2.html">Ukulele 2 - Roy Smeck Method</a></li>
-        <li><a href="/2024/07/02/music.html">Musicians & Artists</a></li>
-        <li><a href="/2024/11/04/zemfira.html">Zemfira</a></li>
-      </ul>
-
-      <h3>Visual Arts</h3>
-      <ul>
-        <li><a href="/2024/07/03/art.html">Art</a></li>
-        <li><a href="/2024/07/04/anime.html">Anime</a></li>
-        <li><a href="/2024/07/01/origami.html">Origami</a></li>
-      </ul>
-
-      <h3>Literature & Film</h3>
-      <ul>
-        <li><a href="/2024/06/30/literature.html">Literature</a></li>
-        <li><a href="/2024/01/05/cinema.html">Cinema</a></li>
-      </ul>
+      <div class="category-content">
+        <h3>Music</h3>
+        <ul>
+          <li><a href="/2024/11/05/music-theory.html">Music Theory</a></li>
+          <li><a href="/2024/07/12/ukulele.html">Ukulele</a></li>
+          <li><a href="/2024/07/12/ukulele-2.html">Ukulele 2 - Roy Smeck Method</a></li>
+          <li><a href="/2024/07/02/music.html">Musicians & Artists</a></li>
+          <li><a href="/2024/11/04/zemfira.html">Zemfira</a></li>
+        </ul>
+
+        <h3>Visual Arts</h3>
+        <ul>
+          <li><a href="/2024/07/03/art.html">Art</a></li>
+          <li><a href="/2024/07/04/anime.html">Anime</a></li>
+          <li><a href="/2024/07/01/origami.html">Origami</a></li>
+        </ul>
+
+        <h3>Literature & Film</h3>
+        <ul>
+          <li><a href="/2024/06/30/literature.html">Literature</a></li>
+          <li><a href="/2024/01/05/cinema.html">Cinema</a></li>
+        </ul>
+      </div>
     </section>
 
     <section>
+      <button class="category-toggle" aria-expanded="true">▼</button>
       <h2>Martial Arts & Wellness</h2>
-
-      <h3>Taijiquan</h3>
-      <ul>
-        <li><a href="/2025/01/06/taijiquan.html">Taijiquan</a></li>
-        <li><a href="/2025/01/05/taijiquan-40-levels.html">Taijiquan 40 Levels</a></li>
-        <li><a href="/2025/04/04/chen.html">Chen Style Taijiquan</a></li>
-        <li><a href="/2024/01/09/taiji-double-weight.html">Taiji Double Weight</a></li>
-      </ul>
-
-      <h3>Physical Activity & Health</h3>
-      <ul>
-        <li><a href="/2024/07/11/health.html">Health & Wellness</a></li>
-        <li><a href="/2024/07/05/bike.html">Biking</a></li>
-      </ul>
+      <div class="category-content">
+        <h3>Taijiquan</h3>
+        <ul>
+          <li><a href="/2025/01/06/taijiquan.html">Taijiquan</a></li>
+          <li><a href="/2025/01/05/taijiquan-40-levels.html">Taijiquan 40 Levels</a></li>
+          <li><a href="/2025/04/04/chen.html">Chen Style Taijiquan</a></li>
+          <li><a href="/2024/01/09/taiji-double-weight.html">Taiji Double Weight</a></li>
+        </ul>
+
+        <h3>Physical Activity & Health</h3>
+        <ul>
+          <li><a href="/2024/07/11/health.html">Health & Wellness</a></li>
+          <li><a href="/2024/07/05/bike.html">Biking</a></li>
+        </ul>
+      </div>
     </section>
 
     <section>
+      <button class="category-toggle" aria-expanded="true">▼</button>
       <h2>Games & Entertainment</h2>
-
-      <h3>Video Games</h3>
-      <ul>
-        <li><a href="/2024/01/01/games.html">Games</a></li>
-        <li><a href="/2025/12/26/nes.html">NES Emulators</a></li>
-      </ul>
-
-      <h3>Card Games</h3>
-      <ul>
-        <li><a href="/2025/04/05/mtg-pauper.html">MTG Pauper</a></li>
-      </ul>
+      <div class="category-content">
+        <h3>Video Games</h3>
+        <ul>
+          <li><a href="/2024/01/01/games.html">Games</a></li>
+          <li><a href="/2025/12/26/nes.html">NES Emulators</a></li>
+        </ul>
+
+        <h3>Card Games</h3>
+        <ul>
+          <li><a href="/2025/04/05/mtg-pauper.html">MTG Pauper</a></li>
+        </ul>
+      </div>
     </section>
 
     <section>
+      <button class="category-toggle" aria-expanded="true">▼</button>
       <h2>Academics & Intellectual Pursuits</h2>
-
-      <h3>Science & Mathematics</h3>
-      <ul>
-        <li><a href="/2024/01/02/science.html">Science</a></li>
-        <li><a href="/2025/04/05/mltt-72.html">Martin-Löf Type Theory (1972)</a></li>
-        <li><a href="/2025/08/28/math-countries.html">Mathematics by Country</a></li>
-      </ul>
-
-      <h3>History & Philosophy</h3>
-      <ul>
-        <li><a href="/2024/01/04/philosophy.html">Philosophy</a></li>
-        <li><a href="/2024/01/06/Karl-Marx.html">Karl Marx</a></li>
-        <li><a href="/2024/01/07/Ivan-Pavlov.html">Ivan Pavlov</a></li>
-      </ul>
+      <div class="category-content">
+        <h3>Science & Mathematics</h3>
+        <ul>
+          <li><a href="/2024/01/02/science.html">Science</a></li>
+          <li><a href="/2025/04/05/mltt-72.html">Martin-Löf Type Theory (1972)</a></li>
+          <li><a href="/2025/08/28/math-countries.html">Mathematics by Country</a></li>
+        </ul>
+
+        <h3>History & Philosophy</h3>
+        <ul>
+          <li><a href="/2024/01/04/philosophy.html">Philosophy</a></li>
+          <li><a href="/2024/01/06/Karl-Marx.html">Karl Marx</a></li>
+          <li><a href="/2024/01/07/Ivan-Pavlov.html">Ivan Pavlov</a></li>
+        </ul>
+      </div>
     </section>
 
     <section>
+      <button class="category-toggle" aria-expanded="true">▼</button>
       <h2>Knowledge & Self-Development</h2>
-
-      <h3>Learning & Organization</h3>
-      <ul>
-        <li><a href="/2025/04/05/organizing-knowledge.html">Organizing Knowledge</a></li>
-        <li><a href="/2024/01/08/epub-fb2.html">EPUB and FB2 Formats</a></li>
-      </ul>
-
-      <h3>Professional Development</h3>
-      <ul>
-        <li><a href="https://github.com/streamcode9/software-design/blob/master/README.md">Principles</a></li>
-      </ul>
+      <div class="category-content">
+        <h3>Learning & Organization</h3>
+        <ul>
+          <li><a href="/2025/04/05/organizing-knowledge.html">Organizing Knowledge</a></li>
+          <li><a href="/2024/01/08/epub-fb2.html">EPUB and FB2 Formats</a></li>
+        </ul>
+
+        <h3>Professional Development</h3>
+        <ul>
+          <li><a href="https://github.com/streamcode9/software-design/blob/master/README.md">Principles</a></li>
+        </ul>
+      </div>
     </section>
 
     <section>
+      <button class="category-toggle" aria-expanded="true">▼</button>
       <h2>Culture & Society</h2>
-
-      <h3>Food & Culinary</h3>
-      <ul>
-        <li><a href="/2025/08/25/sushi.html">Sushi</a></li>
-      </ul>
-
-      <h3>Geography & Travel</h3>
-      <ul>
-        <li><a href="/2024/01/03/countries.html">Countries</a></li>
-      </ul>
-
-      <h3>Home & Family</h3>
-      <ul>
-        <li><a href="/2025/01/28/hus.html">House & Home</a></li>
-        <li><a href="https://github.com/streamcode9/os/blob/main/README.md">Schedule</a></li>
-      </ul>
+      <div class="category-content">
+        <h3>Food & Culinary</h3>
+        <ul>
+          <li><a href="/2025/08/25/sushi.html">Sushi</a></li>
+        </ul>
+
+        <h3>Geography & Travel</h3>
+        <ul>
+          <li><a href="/2024/01/03/countries.html">Countries</a></li>
+        </ul>
+
+        <h3>Home & Family</h3>
+        <ul>
+          <li><a href="/2025/01/28/hus.html">House & Home</a></li>
+          <li><a href="https://github.com/streamcode9/os/blob/main/README.md">Schedule</a></li>
+        </ul>
+      </div>
     </section>
 
     <section>
+      <button class="category-toggle" aria-expanded="true">▼</button>
       <h2>Governance & Politics</h2>
-
-      <h3>Politics & Society</h3>
-      <ul>
-        <li><a href="/2024/01/03/countries.html">Countries</a></li>
-      </ul>
-
-      <h3>Urban Management</h3>
-      <ul>
-        <li>Elections: valgomat</li>
-      </ul>
+      <div class="category-content">
+        <h3>Politics & Society</h3>
+        <ul>
+          <li><a href="/2024/01/03/countries.html">Countries</a></li>
+        </ul>
+
+        <h3>Urban Management</h3>
+        <ul>
+          <li>Elections: valgomat</li>
+        </ul>
+      </div>
     </section>
 
     <section>
+      <button class="category-toggle" aria-expanded="true">▼</button>
       <h2>Ecology & Sustainability</h2>
-      <ul>
-        <li><a href="https://en.wikipedia.org/wiki/Sustainability">Sustainability</a></li>
-      </ul>
+      <div class="category-content">
+        <ul>
+          <li><a href="https://en.wikipedia.org/wiki/Sustainability">Sustainability</a></li>
+        </ul>
+      </div>
     </section>
 
     <section>
+      <button class="category-toggle" aria-expanded="true">▼</button>
       <h2>Future Topics</h2>
-
-      <h3>Available Categories</h3>
-      <ul>
-        <li>Financial Literacy</li>
-        <li>Management and Leadership</li>
-        <li>Information Security</li>
-        <li>Media and Communications</li>
-        <li>Cross-Cultural Communication</li>
-        <li>Ethics and Morality</li>
-        <li>Emotional Sphere and Psychology</li>
-        <li>Interpersonal Relationships</li>
-      </ul>
+      <div class="category-content">
+        <h3>Available Categories</h3>
+        <ul>
+          <li>Financial Literacy</li>
+          <li>Management and Leadership</li>
+          <li>Information Security</li>
+          <li>Media and Communications</li>
+          <li>Cross-Cultural Communication</li>
+          <li>Ethics and Morality</li>
+          <li>Emotional Sphere and Psychology</li>
+          <li>Interpersonal Relationships</li>
+        </ul>
+      </div>
     </section>
 
     <section>
+      <button class="category-toggle" aria-expanded="true">▼</button>
       <h2>Misc</h2>
-      <ul>
-        <li><a href="/pages/blog.html">Latest posts</a></li>
-      </ul>
+      <div class="category-content">
+        <ul>
+          <li><a href="/pages/blog.html">Latest posts</a></li>
+        </ul>
+      </div>
     </section>
   </main>
   <footer class="site-footer">
     <small>&copy; 2025 Streamcode9</small>
   </footer>
+  <script>
+    document.querySelectorAll('.category-toggle').forEach(button => {
+      button.addEventListener('click', function() {
+        const content = this.nextElementSibling.nextElementSibling;
+        const isExpanded = this.getAttribute('aria-expanded') === 'true';
+
+        this.setAttribute('aria-expanded', !isExpanded);
+        content.classList.toggle('collapsed');
+      });
+    });
+  </script>
 </body>
 </html>