OC nav: adaptive — nav + mobile menu flip to dark frosted with light text over dark sections

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

index.html

@@ -252,6 +252,20 @@
     });
     for (var a of menu.querySelectorAll('a')) { a.addEventListener('click', closeMenu); }
   }
+  var nav = document.getElementById('nav');
+  var sections = Array.prototype.slice.call(document.querySelectorAll('[data-bg]'));
+  function updateNavTheme() {
+    var dark = false;
+    for (var s of sections) {
+      var r = s.getBoundingClientRect();
+      if (r.top <= 30 && r.bottom > 30) { dark = (s.dataset.bg === 'dark'); break; }
+    }
+    nav.classList.toggle('on-dark', dark);
+    if (menu) menu.classList.toggle('on-dark', dark);
+  }
+  updateNavTheme();
+  window.addEventListener('scroll', function () { window.requestAnimationFrame(updateNavTheme); }, { passive: true });
+  window.addEventListener('resize', updateNavTheme);
 })();
 </script>