diff --git a/theme/blog_share_theme_coffee.css b/theme/blog_share_theme_coffee.css
index 268b61f..3bc56ca 100644
--- a/theme/blog_share_theme_coffee.css
+++ b/theme/blog_share_theme_coffee.css
@@ -1885,4 +1885,15 @@ html.theme-light .mermaid svg .cluster-label text {
 .hljs-name { color: #ffda92; }
 .hljs-attr { color: #cf90a2; }
 html.theme-light .hljs-name { color: #8e2d53; }
-html.theme-light .hljs-attr { color: #4f6b00; }
\ No newline at end of file
+html.theme-light .hljs-attr { color: #4f6b00; }
+/* ---------- Mobile: Menu always on top (above 3D viewer overlays) ---------- */
+@media (max-width: 48em) {
+    #left-pane,
+    #toc-pane {
+        z-index: 1000;
+    }
+    #header {
+        position: relative;
+        z-index: 1000;
+    }
+}
diff --git a/theme/blog_share_theme_gruvbox.css b/theme/blog_share_theme_gruvbox.css
index fa11f63..802c41d 100644
--- a/theme/blog_share_theme_gruvbox.css
+++ b/theme/blog_share_theme_gruvbox.css
@@ -1885,4 +1885,15 @@ html.theme-light .mermaid svg .cluster-label text {
 .hljs-name { color: #fabd2f; }
 .hljs-attr { color: #83a598; }
 html.theme-light .hljs-name { color: #076678; }
-html.theme-light .hljs-attr { color: #427b58; }
\ No newline at end of file
+html.theme-light .hljs-attr { color: #427b58; }
+/* ---------- Mobile: Menu always on top (above 3D viewer overlays) ---------- */
+@media (max-width: 48em) {
+    #left-pane,
+    #toc-pane {
+        z-index: 1000;
+    }
+    #header {
+        position: relative;
+        z-index: 1000;
+    }
+}
diff --git a/theme/blog_share_theme_harbor.css b/theme/blog_share_theme_harbor.css
index 48eed42..9b59347 100644
--- a/theme/blog_share_theme_harbor.css
+++ b/theme/blog_share_theme_harbor.css
@@ -1885,4 +1885,15 @@ html.theme-light .mermaid svg .cluster-label text {
 .hljs-name { color: #E1CE98; }
 .hljs-attr { color: #77838a; }
 html.theme-light .hljs-name { color: #4c6c94; }
-html.theme-light .hljs-attr { color: #556753; }
\ No newline at end of file
+html.theme-light .hljs-attr { color: #556753; }
+/* ---------- Mobile: Menu always on top (above 3D viewer overlays) ---------- */
+@media (max-width: 48em) {
+    #left-pane,
+    #toc-pane {
+        z-index: 1000;
+    }
+    #header {
+        position: relative;
+        z-index: 1000;
+    }
+}
diff --git a/theme/blog_share_theme_solarized.css b/theme/blog_share_theme_solarized.css
index 2e74049..b673f32 100644
--- a/theme/blog_share_theme_solarized.css
+++ b/theme/blog_share_theme_solarized.css
@@ -1890,4 +1890,15 @@ html.theme-light .mermaid svg .cluster-label text {
 .hljs-name { color: #b58900; }
 .hljs-attr { color: #839496; }
 html.theme-light .hljs-name { color: #268bd2; }
-html.theme-light .hljs-attr { color: #586e75; }
\ No newline at end of file
+html.theme-light .hljs-attr { color: #586e75; }
+/* ---------- Mobile: Menu always on top (above 3D viewer overlays) ---------- */
+@media (max-width: 48em) {
+    #left-pane,
+    #toc-pane {
+        z-index: 1000;
+    }
+    #header {
+        position: relative;
+        z-index: 1000;
+    }
+}
diff --git a/theme/blog_share_theme_tokyonight.css b/theme/blog_share_theme_tokyonight.css
index 8581ccd..e755d8a 100644
--- a/theme/blog_share_theme_tokyonight.css
+++ b/theme/blog_share_theme_tokyonight.css
@@ -1890,4 +1890,15 @@ html.theme-light .mermaid svg .cluster-label text {
 .hljs-name { color: #e0af68; }
 .hljs-attr { color: #a9b1d6; }
 html.theme-light .hljs-name { color: #2e7de9; }
-html.theme-light .hljs-attr { color: #a0a6c2; }
\ No newline at end of file
+html.theme-light .hljs-attr { color: #a0a6c2; }
+/* ---------- Mobile: Menu always on top (above 3D viewer overlays) ---------- */
+@media (max-width: 48em) {
+    #left-pane,
+    #toc-pane {
+        z-index: 1000;
+    }
+    #header {
+        position: relative;
+        z-index: 1000;
+    }
+}