add darkmode

pages/techniques.html

@@ -19,9 +19,33 @@
       <a href="prompts.html">Prompt Guide</a>
       <a href="math.html">Math & Concepts</a>
     </div>
+    <button class="dark-toggle" id="darkToggle" aria-label="Toggle dark mode">🌙</button>
   </div>
 </nav>
 
+<script>
+(function(){
+  var btn = document.getElementById('darkToggle');
+  var saved = localStorage.getItem('theme');
+  if(saved === 'dark' || (!saved && window.matchMedia('(prefers-color-scheme: dark)').matches)){
+    document.documentElement.setAttribute('data-theme','dark');
+    btn.textContent = '☀️';
+  }
+  btn.addEventListener('click', function(){
+    var isDark = document.documentElement.getAttribute('data-theme') === 'dark';
+    if(isDark){
+      document.documentElement.removeAttribute('data-theme');
+      btn.textContent = '🌙';
+      localStorage.setItem('theme','light');
+    } else {
+      document.documentElement.setAttribute('data-theme','dark');
+      btn.textContent = '☀️';
+      localStorage.setItem('theme','dark');
+    }
+  });
+})();
+</script>
+
 <div class="hero">
   <h1>AI Techniques</h1>
   <p>How AI models are built, trained, and optimized.</p>