diff --git a/css/style.css b/css/style.css
index aad9283e..3ed82754 100644
--- a/css/style.css
+++ b/css/style.css
@@ -1419,26 +1419,52 @@ footer a:hover {
   left: 0;
   width: 16rem; /* Tailwind's w-64 */
   height: 100vh;
+  height: 100dvh;
   background-color: #0f172a;
   overflow-y: auto;
   -webkit-overflow-scrolling: touch;
-  transition: transform 0.3s ease;
+  transition: transform 0.3s ease, box-shadow 0.3s ease;
+  /* Keep below modal stacks (z-50+) so dialogs overlay the drawer. */
+  z-index: 40;
+  box-shadow: none;
+}
+
+#sidebar.sidebar-open {
+  box-shadow: 0 0.75rem 1.5rem rgba(15, 23, 42, 0.45);
+}
+
+#sidebarOverlay {
+  position: fixed;
+  top: 0;
+  left: 0;
+  right: 0;
+  bottom: 0;
+  background: rgba(15, 23, 42, 0.55);
+  opacity: 0;
+  pointer-events: none;
+  transition: opacity 0.3s ease;
+  /* Sits above page chrome but below modals and the sidebar itself. */
+  z-index: 30;
+}
+
+body.sidebar-open #sidebarOverlay {
+  opacity: 1;
+  pointer-events: auto;
 }
 
 /* Mobile (max-width: 767px): Hide sidebar by default */
 @media (max-width: 767px) {
   #sidebar {
-    transform: translateX(-100%);
+    transform: translate3d(-100%, 0, 0);
+    width: min(16rem, calc(100vw - 3rem));
   }
   /* When the sidebar-open class is added, slide the sidebar in */
   #sidebar.sidebar-open {
-    transform: translateX(0);
+    transform: translate3d(0, 0, 0);
   }
 
-  /* Optionally shift main content when sidebar is open */
-  #app.sidebar-open {
-    transform: translateX(16rem);
-    transition: transform 0.3s ease;
+  body.sidebar-open {
+    overflow: hidden;
   }
 }
 
@@ -1447,6 +1473,14 @@ footer a:hover {
   #sidebar {
     transform: translateX(0) !important;
   }
+
+  #sidebar.sidebar-open {
+    box-shadow: none;
+  }
+
+  #sidebarOverlay {
+    display: none;
+  }
 }
 
 /* Collapsed/expanded classes if needed on desktop */
diff --git a/index.html b/index.html
index 20d0a02f..77d2206f 100644
--- a/index.html
+++ b/index.html
@@ -51,19 +51,21 @@
     <link href="css/markdown.css" rel="stylesheet" />
   </head>
   <body class="bg-gray-100">
-    <!-- 
+    <!--
       SIDEBAR CONTAINER:
-      The <aside id="sidebar"> inside handles visibility. 
+      The <aside id="sidebar"> inside handles visibility.
       By default, no special position or z-index on #sidebarContainer.
     -->
     <div id="sidebarContainer">
       <!-- components/sidebar.html gets injected here -->
     </div>
 
-    <!-- 
+    <div id="sidebarOverlay" class="md:hidden" aria-hidden="true"></div>
+
+    <!--
       MAIN CONTENT:
       md:ml-64 ensures content is shifted on desktop so the pinned sidebar doesn't overlap.
-      On mobile, we also toggle .sidebar-open to shift the entire content.
+      On mobile we float the sidebar over the content and dim the background overlay.
     -->
     <!--
       `fade-in` is scrubbed by js/index.js after the first animation so that
@@ -84,6 +86,10 @@
         <button
           id="mobileMenuBtn"
           class="md:hidden ml-2 mr-4 flex items-center justify-center w-10 h-10 rounded-full bg-transparent hover:bg-transparent focus:outline-none focus:ring-2 focus:ring-[#0f172a] z-[60] fade-in"
+          type="button"
+          aria-expanded="false"
+          aria-controls="sidebar"
+          aria-label="Toggle navigation menu"
         >
           <img
             src="assets/svg/mobile-sidebar-menu-icon.svg"
diff --git a/js/index.js b/js/index.js
index c1224d2f..b62cb70f 100644
--- a/js/index.js
+++ b/js/index.js
@@ -170,12 +170,61 @@ async function bootstrapInterface() {
 
   const mobileMenuBtn = document.getElementById("mobileMenuBtn");
   const sidebar = document.getElementById("sidebar");
-  const appElement = document.getElementById("app");
-  if (mobileMenuBtn && sidebar && appElement) {
-    mobileMenuBtn.addEventListener("click", () => {
-      sidebar.classList.toggle("sidebar-open");
-      appElement.classList.toggle("sidebar-open");
-    });
+  const sidebarOverlay = document.getElementById("sidebarOverlay");
+
+  const setSidebarState = (isOpen) => {
+    if (sidebar) {
+      sidebar.classList.toggle("sidebar-open", isOpen);
+    }
+    document.body.classList.toggle("sidebar-open", isOpen);
+    if (mobileMenuBtn) {
+      mobileMenuBtn.setAttribute("aria-expanded", isOpen ? "true" : "false");
+    }
+  };
+
+  const closeSidebar = () => setSidebarState(false);
+  const isMobileViewport = () => {
+    if (typeof window.matchMedia === "function") {
+      return window.matchMedia("(max-width: 767px)").matches;
+    }
+    return window.innerWidth < 768;
+  };
+
+  const toggleSidebar = () => {
+    if (!sidebar) return;
+    const isMobile = isMobileViewport();
+    if (!isMobile) return;
+    const shouldOpen = !sidebar.classList.contains("sidebar-open");
+    setSidebarState(shouldOpen);
+  };
+
+  if (mobileMenuBtn && sidebar) {
+    mobileMenuBtn.addEventListener("click", toggleSidebar);
+  }
+
+  if (sidebarOverlay) {
+    sidebarOverlay.addEventListener("click", closeSidebar);
+  }
+
+  document.addEventListener("keydown", (event) => {
+    if (event.key === "Escape" && sidebar && sidebar.classList.contains("sidebar-open")) {
+      closeSidebar();
+    }
+  });
+
+  if (typeof window.matchMedia === "function") {
+    const desktopQuery = window.matchMedia("(min-width: 768px)");
+    const onDesktopChange = (event) => {
+      if (event.matches) {
+        closeSidebar();
+      }
+    };
+
+    if (typeof desktopQuery.addEventListener === "function") {
+      desktopQuery.addEventListener("change", onDesktopChange);
+    } else if (typeof desktopQuery.addListener === "function") {
+      desktopQuery.addListener(onDesktopChange);
+    }
   }
 
   const footerDropdownButton = document.getElementById("footerDropdownButton");
@@ -195,7 +244,7 @@ async function bootstrapInterface() {
   try {
     const sidebarModule = await import("./sidebar.js");
     if (typeof sidebarModule.setupSidebarNavigation === "function") {
-      sidebarModule.setupSidebarNavigation();
+      sidebarModule.setupSidebarNavigation({ closeSidebar });
     }
   } catch (error) {
     console.error("Failed to set up sidebar navigation:", error);
diff --git a/js/sidebar.js b/js/sidebar.js
index adb6f5cd..76301a70 100644
--- a/js/sidebar.js
+++ b/js/sidebar.js
@@ -1,7 +1,7 @@
 // sidebar.js
 import { setHashView } from "./index.js";
 
-export function setupSidebarNavigation() {
+export function setupSidebarNavigation({ closeSidebar } = {}) {
   const sidebarLinks = document.querySelectorAll('#sidebar a[href^="#view="]');
   sidebarLinks.forEach((link) => {
     link.addEventListener("click", (e) => {
@@ -16,13 +16,21 @@ export function setupSidebarNavigation() {
       setHashView(viewName); // This changes the hash and loads the view.
 
       // --- NEW: if on mobile, close the sidebar automatically. ---
-      if (window.innerWidth < 768) {
-        const sidebar = document.getElementById("sidebar");
-        const app = document.getElementById("app");
-        if (sidebar && app) {
-          sidebar.classList.remove("sidebar-open");
-          app.classList.remove("sidebar-open");
+      const isMobile =
+        typeof window.matchMedia === "function"
+          ? window.matchMedia("(max-width: 767px)").matches
+          : window.innerWidth < 768;
+      if (isMobile) {
+        if (typeof closeSidebar === "function") {
+          closeSidebar();
+          return;
         }
+
+        const sidebar = document.getElementById("sidebar");
+        if (sidebar) {
+          sidebar.classList.remove("sidebar-open");
+        }
+        document.body.classList.remove("sidebar-open");
       }
     });
   });