diff --git a/docs/static/style.css b/docs/static/style.css
index de6535b..b98670d 100644
--- a/docs/static/style.css
+++ b/docs/static/style.css
@@ -136,6 +136,20 @@ body {
   color: var(--accent);
 }
 
+/* CSS-only scrollspy (progressive enhancement)
+ * Uses CSS Overflow Level 5: scroll-target-group + :target-current
+ * Browser support: Chrome 140+, Edge 140+, Opera 124+
+ * Graceful degradation: unsupported browsers ignore these properties
+ */
+.sidebar .nav-anchors {
+  scroll-target-group: auto;
+}
+
+.sidebar .nav-anchors .anchor-link:target-current {
+  color: var(--accent);
+  font-weight: 600;
+}
+
 /* Indent anchors by heading level */
 .sidebar .nav-anchors .level-3 {
   margin-left: 0.5rem;