diff --git a/hermes-custom.css b/hermes-custom.css
new file mode 100644
index 0000000..7252998
--- /dev/null
+++ b/hermes-custom.css
@@ -0,0 +1,146 @@
+/* HermesCustom CSS — Lukas' responsive-layout additions for obsidian-web-viewer.
+ *
+ * Loaded via <link rel="stylesheet"> in vault.html (one-line patch)
+ * BEFORE obv's main <style>, so that our rules apply at first paint
+ * (no FOUC, no layout shift).
+ *
+ * Layout classes (toggled by vault-custom.js):
+ *   .hermes-rc               — base marker (added once)
+ *   .hermes-mobile           — <768px viewport (tree=hamburger, graph=bottom-panel)
+ *   .hermes-tablet           — 768-1023px (tree=visible, graph=bottom-panel)
+ *   .hermes-desktop          — >=1024px (3-panel layout, no overrides)
+ *
+ * Sidebar state:
+ *   .hermes-sidebar-open     — hamburger toggled (mobile only)
+ *
+ * Strategy: every selector starts with `.vault-app.hermes-rc` to win
+ * specificity against obv's `.vault-app` only.
+ */
+
+/* === Always-on (no media query) === */
+.vault-app.hermes-rc {
+    box-sizing: border-box !important;
+    width: 100% !important;
+    max-width: 100vw !important;
+    overflow-x: hidden !important;
+}
+.vault-app.hermes-rc .vault-content {
+    overflow-x: hidden !important;
+    overflow-y: auto !important;
+    max-width: 100% !important;
+    word-wrap: break-word !important;
+    overflow-wrap: break-word !important;
+    hyphens: auto !important;
+}
+.vault-app.hermes-rc .vault-sidebar {
+    overflow-x: hidden !important;
+    overflow-y: auto !important;
+}
+.vault-app.hermes-rc .vault-graph {
+    position: relative !important;
+    overflow: hidden !important;
+}
+
+/* Hamburger button (hidden by default, shown only in mobile) */
+.hermes-mobile-toggle {
+    display: none;
+    background: var(--bg-secondary);
+    border: 1px solid var(--border);
+    color: var(--text-secondary);
+    padding: 6px 12px;
+    border-radius: 4px;
+    cursor: pointer;
+    font-size: 16px;
+    margin-right: 8px;
+    line-height: 1;
+}
+.hermes-mobile-toggle:hover {
+    color: var(--accent);
+    border-color: var(--accent);
+}
+
+/* === Mobile (<768px) — tree hamburger + graph bottom-panel === */
+@media (max-width: 767px) {
+    .vault-app.hermes-rc.hermes-mobile {
+        grid-template-columns: 1fr !important;
+        grid-template-rows: 48px 1fr 140px !important;
+        height: 100vh !important;
+    }
+    .vault-app.hermes-rc.hermes-mobile .vault-sidebar {
+        position: fixed !important;
+        top: 48px !important;
+        left: 0 !important;
+        bottom: 0 !important;
+        width: 280px !important;
+        max-width: 85vw !important;
+        transform: translateX(-100%) !important;
+        transition: transform 0.25s ease-in-out !important;
+        z-index: 1000 !important;
+        background: var(--bg-secondary) !important;
+        border-right: 1px solid var(--border) !important;
+        display: block !important;
+        height: calc(100vh - 48px) !important;
+    }
+    .vault-app.hermes-rc.hermes-mobile .vault-sidebar.hermes-sidebar-open {
+        transform: translateX(0) !important;
+    }
+    .vault-app.hermes-rc.hermes-mobile .vault-graph {
+        grid-column: 1 / -1 !important;
+        grid-row: 3 !important;
+        height: 140px !important;
+        border-left: none !important;
+        border-top: 1px solid var(--border) !important;
+        display: block !important; /* keep visible, just at bottom */
+    }
+    .vault-app.hermes-rc.hermes-mobile .vault-content {
+        grid-column: 1 !important;
+        grid-row: 2 !important;
+        padding: 16px 20px !important;
+        max-width: 100% !important;
+    }
+    .vault-app.hermes-rc.hermes-mobile .hermes-mobile-toggle {
+        display: inline-block !important;
+    }
+    /* Backdrop for open hamburger */
+    .hermes-sidebar-backdrop {
+        display: none;
+        position: fixed;
+        top: 48px;
+        left: 0;
+        right: 0;
+        bottom: 0;
+        background: rgba(0, 0, 0, 0.5);
+        z-index: 999;
+    }
+    .vault-app.hermes-rc.hermes-mobile .hermes-sidebar-backdrop.hermes-backdrop-visible {
+        display: block;
+    }
+}
+
+/* === Tablet (768px-1023px) — tree visible, graph bottom-panel === */
+@media (min-width: 768px) and (max-width: 1023px) {
+    .vault-app.hermes-rc.hermes-tablet {
+        grid-template-columns: 200px 1fr !important;
+        grid-template-rows: 48px 1fr 200px !important;
+        height: 100vh !important;
+    }
+    .vault-app.hermes-rc.hermes-tablet .vault-sidebar {
+        width: 200px !important;
+        max-width: 200px !important;
+    }
+    .vault-app.hermes-rc.hermes-tablet .vault-graph {
+        grid-column: 1 / -1 !important;
+        grid-row: 3 !important;
+        height: 200px !important;
+        border-left: none !important;
+        border-top: 1px solid var(--border) !important;
+    }
+    .vault-app.hermes-rc.hermes-tablet .vault-content {
+        grid-column: 2 !important;
+        grid-row: 2 !important;
+        padding: 20px 28px !important;
+    }
+}
+
+/* === Desktop (≥1024px) — leave obv default layout === */
+/* No overrides needed; we just mark .hermes-desktop class so JS knows */
diff --git a/vault-custom.js b/vault-custom.js
index 9874426..cfd9e7a 100644
--- a/vault-custom.js
+++ b/vault-custom.js
@@ -1,6 +1,6 @@
 /* HermesCustom — Lukas' additions to obsidian-web-viewer
  *
- * Loaded by vault.html (one-line patch) AFTER the main script. Initializes
+ * Loaded by vault.html via <script> tag (one-line patch). Initializes
  * automatically via HermesCustom.init() at the bottom of this file.
  *
  * Features:
@@ -9,12 +9,9 @@
  *   3. Responsive layout (graph collapses below 1024px, tree below 768px)
  *   4. URL-based navigation (?file=<path>)
  *
- * Design notes: see docs/ARCHITECTURE.md
+ * Companion file: hermes-custom.css (loaded externally via <link>)
  *
- * IMPORTANT: This script runs AFTER obv's main script (which sets up the
- * layout). So our responsiveLayout() needs to apply classes/styles AFTER
- * obv's setup, and our CSS must win the specificity battle against obv's
- * inline styles + media queries.
+ * Design notes: see docs/ARCHITECTURE.md
  */
 (function() {
     'use strict';
@@ -33,155 +30,39 @@
     };
 
     // ============================================================
-    // 1. CSS injection — high specificity to win against obv
+    // 1. CSS injection — now no-op since CSS is loaded externally
     // ============================================================
 
     /**
-     * Inject responsive CSS into <head> as a stylesheet (not <style>), so
-     * the cascade is well-defined. We use:
-     *   - High specificity selectors (extra class chains)
-     *   - !important on critical layout properties
-     *   - CSS variables that we toggle via JS
-     *
-     * Strategy: we add a class `hermes-rc` (hermes responsive container) to
-     * the .vault-app element. All our CSS rules start with `.vault-app.hermes-rc`
-     * to beat obv's `.vault-app` selectors.
+     * CSS lives in hermes-custom.css (loaded via <link> in vault.html).
+     * This method remains as a no-op for backward-compat / fallback.
      */
     HermesCustom.injectResponsiveCSS = function() {
-        if (document.getElementById('hermes-custom-css')) return;
-
-        // Wait until <head> exists
-        const head = document.head || document.getElementsByTagName('head')[0];
-        if (!head) {
-            setTimeout(HermesCustom.injectResponsiveCSS, 10);
-            return;
-        }
-
-        const style = document.createElement('style');
-        style.id = 'hermes-custom-css';
-        style.textContent = `
-/* === Hermes Custom: always-applied base (no media query) === */
-.vault-app.hermes-rc {
-    box-sizing: border-box !important;
-    width: 100% !important;
-    max-width: 100vw !important;
-    overflow-x: hidden !important;   /* prevent horizontal scroll on mobile */
-}
-.vault-app.hermes-rc .vault-content {
-    overflow-x: hidden !important;   /* content scrolls vertically only */
-    overflow-y: auto !important;
-    max-width: 100% !important;
-    word-wrap: break-word !important; /* long URLs/codes don't overflow */
-    overflow-wrap: break-word !important;
-}
-.vault-app.hermes-rc .vault-sidebar {
-    overflow-x: hidden !important;
-    overflow-y: auto !important;
-    max-width: 280px !important;
-}
-.vault-app.hermes-rc .vault-graph {
-    overflow: hidden !important;
-    position: relative !important;
-}
-
-/* === Mobile (<768px) === */
-.vault-app.hermes-rc.hermes-mobile {
-    grid-template-columns: 1fr !important;
-    grid-template-rows: 48px 1fr !important;
-}
-.vault-app.hermes-rc.hermes-mobile .vault-sidebar {
-    position: fixed !important;
-    top: 48px !important;
-    left: 0 !important;
-    bottom: 0 !important;
-    width: 280px !important;
-    max-width: 85vw !important;
-    transform: translateX(-100%) !important;
-    transition: transform 0.2s ease !important;
-    z-index: 1000 !important;
-    background: var(--bg-secondary) !important;
-    border-right: 1px solid var(--border) !important;
-    display: block !important;
-}
-.vault-app.hermes-rc.hermes-mobile .vault-sidebar.hermes-sidebar-open {
-    transform: translateX(0) !important;
-}
-.vault-app.hermes-rc.hermes-mobile .vault-graph {
-    display: none !important;
-}
-.vault-app.hermes-rc.hermes-mobile .vault-content {
-    grid-column: 1 !important;
-    padding: 16px 20px !important;
-    max-width: 100% !important;
-}
-.hermes-mobile-toggle {
-    display: none;
-    background: var(--bg-secondary);
-    border: 1px solid var(--border);
-    color: var(--text-secondary);
-    padding: 6px 12px;
-    border-radius: 4px;
-    cursor: pointer;
-    font-size: 14px;
-    margin-right: 8px;
-}
-.vault-app.hermes-rc.hermes-mobile .hermes-mobile-toggle { display: inline-block !important; }
-
-/* === Tablet (768px-1023px) === */
-.vault-app.hermes-rc.hermes-tablet {
-    grid-template-columns: 200px 1fr !important;
-    grid-template-rows: 48px 1fr 220px !important;
-    height: 100vh !important;
-}
-.vault-app.hermes-rc.hermes-tablet .vault-sidebar {
-    width: 200px !important;
-    max-width: 200px !important;
-}
-.vault-app.hermes-rc.hermes-tablet .vault-graph {
-    grid-column: 1 / -1 !important;
-    grid-row: 3 !important;
-    height: 220px !important;
-    border-left: none !important;
-    border-top: 1px solid var(--border) !important;
-}
-.vault-app.hermes-rc.hermes-tablet .vault-content {
-    grid-column: 2 !important;
-    grid-row: 2 !important;
-    padding: 20px 28px !important;
-}
-
-/* === Desktop (≥1024px): leave obv's default layout alone === */
-.vault-app.hermes-rc.hermes-desktop {
-    /* inherit obv's grid */
-}
-        `;
-        head.appendChild(style);
-        console.log('[HermesCustom] CSS injected');
+        // No-op: CSS loaded externally via <link rel="stylesheet"> in vault.html
     };
 
     // ============================================================
-    // 2. Layout application — called on init and on resize
+    // 2. Layout application
     // ============================================================
 
     HermesCustom.applyLayout = function() {
         const app = document.querySelector('.vault-app');
         if (!app) {
-            // obv not loaded yet, retry
             setTimeout(HermesCustom.applyLayout, 100);
             return;
         }
 
-        // Add our marker class (specificity booster)
+        // Add marker class (specificity booster)
         if (!app.classList.contains('hermes-rc')) {
             app.classList.add('hermes-rc');
         }
 
         const width = window.innerWidth;
-        // Remove all mode classes
         app.classList.remove('hermes-mobile', 'hermes-tablet', 'hermes-desktop');
-        // Sidebar state reset
         const sidebar = document.querySelector('.vault-sidebar');
         if (sidebar) sidebar.classList.remove('hermes-sidebar-open');
+        const backdrop = document.querySelector('.hermes-sidebar-backdrop');
+        if (backdrop) backdrop.classList.remove('hermes-backdrop-visible');
 
         if (width < BREAKPOINTS.mobile) {
             app.classList.add('hermes-mobile');
@@ -191,7 +72,6 @@
             app.classList.add('hermes-desktop');
         }
 
-        // Add hamburger toggle in mobile mode
         if (width < BREAKPOINTS.mobile) {
             HermesCustom.ensureHamburgerButton();
         }
@@ -201,6 +81,19 @@
         if (document.querySelector('.hermes-mobile-toggle')) return;
         const header = document.querySelector('.vault-header');
         if (!header) return;
+
+        // Backdrop (click-outside-to-close)
+        if (!document.querySelector('.hermes-sidebar-backdrop')) {
+            const backdrop = document.createElement('div');
+            backdrop.className = 'hermes-sidebar-backdrop';
+            backdrop.onclick = () => {
+                const sidebar = document.querySelector('.vault-sidebar');
+                if (sidebar) sidebar.classList.remove('hermes-sidebar-open');
+                backdrop.classList.remove('hermes-backdrop-visible');
+            };
+            document.body.appendChild(backdrop);
+        }
+
         const btn = document.createElement('button');
         btn.className = 'hermes-mobile-toggle';
         btn.textContent = '☰';
@@ -208,12 +101,16 @@
         btn.onclick = (e) => {
             e.stopPropagation();
             const sidebar = document.querySelector('.vault-sidebar');
-            if (sidebar) sidebar.classList.toggle('hermes-sidebar-open');
+            const backdrop = document.querySelector('.hermes-sidebar-backdrop');
+            if (sidebar) {
+                sidebar.classList.toggle('hermes-sidebar-open');
+                if (backdrop) backdrop.classList.toggle('hermes-backdrop-visible',
+                    sidebar.classList.contains('hermes-sidebar-open'));
+            }
         };
         header.insertBefore(btn, header.firstChild);
     };
 
-    // Throttled resize handler
     HermesCustom.setupResizeHandler = function() {
         let resizeTimer;
         let lastWidth = window.innerWidth;
@@ -247,10 +144,9 @@
         if (!currentFile) return [];
         const graphData = HermesCustom._graphData;
         if (!graphData) return [];
-        const connections = graphData.edges
+        return graphData.edges
             .filter(e => e.source === currentFile)
             .map(e => e.target);
-        return connections;
     };
 
     HermesCustom.highlightCurrentNode = function() {
@@ -272,11 +168,15 @@
                 mesh.material.color.setHex(0xFFD700);
                 mesh.material.emissive.setHex(0xFFD700);
                 mesh.material.emissiveIntensity = 0.6;
+                mesh.material.opacity = 1.0;
+                mesh.material.transparent = false;
                 mesh.scale.set(1.5, 1.5, 1.5);
             } else if (isConnected) {
                 mesh.material.color.setHex(0x89b4fa);
                 mesh.material.emissive.setHex(0x89b4fa);
                 mesh.material.emissiveIntensity = 0.3;
+                mesh.material.opacity = 1.0;
+                mesh.material.transparent = false;
                 mesh.scale.set(1.1, 1.1, 1.1);
             } else {
                 mesh.material.color.setHex(0x313244);
@@ -331,7 +231,7 @@
     };
 
     // ============================================================
-    // 6. loadFile hook — track current file
+    // 6. loadFile hook
     // ============================================================
 
     HermesCustom.hookLoadFile = function() {
@@ -346,6 +246,11 @@
             HermesCustom._lastLoadedFile = path;
             HermesCustom.updateURL(path);
             const result = originalLoadFile.apply(this, arguments);
+            // Close sidebar on mobile after file selection
+            const sidebar = document.querySelector('.vault-sidebar');
+            const backdrop = document.querySelector('.hermes-sidebar-backdrop');
+            if (sidebar) sidebar.classList.remove('hermes-sidebar-open');
+            if (backdrop) backdrop.classList.remove('hermes-backdrop-visible');
             setTimeout(HermesCustom.highlightCurrentNode, 300);
             return result;
         };
@@ -354,7 +259,7 @@
     };
 
     // ============================================================
-    // 7. Graph data fetch (for highlight logic)
+    // 7. Graph data fetch
     // ============================================================
 
     HermesCustom.loadGraphData = function() {
@@ -373,14 +278,12 @@
     // ============================================================
 
     HermesCustom.init = function() {
-        console.log('[HermesCustom] init v2 (responsive-fix)');
+        console.log('[HermesCustom] init v3 (CSS external + responsive-layout)');
         HermesCustom.injectResponsiveCSS();
         HermesCustom.hookLoadFile();
         HermesCustom.applyLayout();
         HermesCustom.setupResizeHandler();
         HermesCustom.loadGraphData();
-
-        // Graph click handler needs Three.js to be ready
         setTimeout(() => {
             HermesCustom.setupGraphClickHandler();
         }, 1500);
@@ -390,8 +293,6 @@
     if (document.readyState === 'loading') {
         document.addEventListener('DOMContentLoaded', HermesCustom.init);
     } else {
-        // DOM already ready — but obv's main script may not have run yet.
-        // Defer slightly to let obv set up the layout first.
         setTimeout(HermesCustom.init, 50);
     }
 
diff --git a/vault.html b/vault.html
index 091c626..748cb78 100644
--- a/vault.html
+++ b/vault.html
@@ -4,6 +4,7 @@
 <meta charset="UTF-8">
 <meta name="viewport" content="width=device-width, initial-scale=1">
 <title>Vault Viewer</title>
+<link rel="stylesheet" href="hermes-custom.css">
 <script src="https://cdn.jsdelivr.net/npm/marked/marked.min.js"></script>
 <script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/r128/three.min.js"></script>
 <style>