Add responsive hamburger menu for mobile

html/index.html

@@ -12,7 +12,12 @@
     <header>
         <nav class="container">
             <a href="#" class="logo">Ground Zero Lab</a>
-            <ul class="nav-links">
+            <div class="hamburger" onclick="toggleHamburger()">
+                <span></span>
+                <span></span>
+                <span></span>
+            </div>
+            <ul class="nav-links" id="navLinks">
                 <li><a href="#about">Über Uns</a></li>
                 <li><a href="#projects">Projekte</a></li>
                 <li><a href="#tech">Technologie</a></li>
@@ -147,5 +152,28 @@
             <p>&copy; 2026 Ground Zero Lab</p>
         </div>
     </footer>
+
+    <script>
+        function toggleHamburger() {
+            const navLinks = document.getElementById('navLinks');
+            navLinks.classList.toggle('mobile-open');
+            
+            const hamburger = document.querySelector('.hamburger');
+            hamburger.classList.toggle('active');
+        }
+
+        // Close mobile menu when clicking on a link
+        document.addEventListener('DOMContentLoaded', function() {
+            const navLinks = document.getElementById('navLinks');
+            const links = navLinks.querySelectorAll('a');
+            
+            links.forEach(link => {
+                link.addEventListener('click', function() {
+                    navLinks.classList.remove('mobile-open');
+                    document.querySelector('.hamburger').classList.remove('active');
+                });
+            });
+        });
+    </script>
 </body>
 </html>