diff --git a/public/js/nav.js b/public/js/nav.js
new file mode 100644
index 0000000..61df352
--- /dev/null
+++ b/public/js/nav.js
@@ -0,0 +1,13 @@
+function applyHeaderShadow() {
+  const header = document.querySelector(".web-header-emit-shadow-when-top");
+  if (!header) return;
+
+  window.addEventListener("scroll", () => {
+    if (window.scrollY > 0) {
+      header.classList.add("shadow-active");
+    } else {
+      header.classList.remove("shadow-active");
+    }
+  });
+}
+document.addEventListener("DOMContentLoaded", applyHeaderShadow);
\ No newline at end of file