diff --git a/public/styles.css b/public/styles.css
index d5d66d6..d30603b 100755
--- a/public/styles.css
+++ b/public/styles.css
@@ -3,6 +3,7 @@
   --fg: #e6e3d7;
   --accent: #e0b84b;
   --topbar-h: 56px;
+  --subnav-h: 44px;
   --transition: .3s ease;
   --radius: 8px;
 }
@@ -47,8 +48,44 @@ html, body {
   text-shadow: 0 0 8px var(--accent);
 }
 
+/* HORIZON LAYER: Sub-Navigation */
+.sub-nav {
+  display: none;
+  position: fixed;
+  top: var(--topbar-h);
+  left: 0; right: 0;
+  height: var(--subnav-h);
+  background: #0e0e0e;
+  border-bottom: 1px solid #222;
+  padding: 0 1rem;
+  gap: 1rem;
+  overflow-x: auto;
+  white-space: nowrap;
+  z-index: 950;
+  align-items: center;
+  opacity: 0;
+  transition: opacity var(--transition);
+}
+
+.sub-nav.visible {
+  display: flex;
+  opacity: 1;
+}
+
+.sub-nav a {
+  color: var(--accent);
+  text-decoration: none;
+  font-weight: 500;
+  font-size: 0.95rem;
+  transition: all var(--transition);
+}
+
+.sub-nav a:hover {
+  text-shadow: 0 0 6px var(--accent);
+}
+
 #sidebar {
-  position: fixed; top: var(--topbar-h); left: 0;
+  position: fixed; top: calc(var(--topbar-h) + var(--subnav-h)); left: 0;
   width: 300px; bottom: 0; overflow: auto;
   background: #111; border-right: 1px solid #222;
   transform: translateX(-100%); transition: transform var(--transition);
@@ -124,14 +161,14 @@ body.sidebar-open #sidebar { transform: translateX(0); }
 }
 
 .content {
-  margin-top: var(--topbar-h); margin-left: 0;
-  transition: margin-left var(--transition);
-  min-height: calc(100vh - var(--topbar-h));
+  margin-top: calc(var(--topbar-h) + var(--subnav-h)); margin-left: 0;
+  transition: margin-left var(--transition), margin-top var(--transition);
+  min-height: calc(100vh - var(--topbar-h) - var(--subnav-h));
   padding: 2rem 1rem;
 }
 
 @media (min-width: 1024px) {
-  #sidebar { transform: translateX(0); }
+  #sidebar { transform: translateX(0); top: calc(var(--topbar-h) + var(--subnav-h)); }
   .content { margin-left: 300px; }
 }
 
@@ -146,7 +183,7 @@ body.sidebar-open #sidebar { transform: translateX(0); }
 }
 
 .viewer iframe {
-  width: 100%; height: calc(100vh - var(--topbar-h) - 80px);
+  width: 100%; height: calc(100vh - var(--topbar-h) - var(--subnav-h) - 80px);
   border: 0; border-radius: var(--radius); background: transparent;
   display: block;
 }
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