6 changed files with 188 additions and 0 deletions
--- a/icons/icon-192.png
+++ b/icons/icon-192.png
--- a/icons/icon-512.png
+++ b/icons/icon-512.png
--- a/index.html
+++ b/index.html
@@ -19,6 +19,13 @@
 <meta charset="UTF-8">
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
 <title>The Nexus — Timmy's Sovereign Home</title>
+<link rel="manifest" href="./manifest.json">
+<meta name="theme-color" content="#4af0c0">
+<meta name="mobile-web-app-capable" content="yes">
+<meta name="apple-mobile-web-app-capable" content="yes">
+<meta name="apple-mobile-web-app-status-bar-style" content="black-translucent">
+<meta name="apple-mobile-web-app-title" content="The Nexus">
+<link rel="apple-touch-icon" href="./icons/icon-192.png">
 <link rel="preconnect" href="https://fonts.googleapis.com">
 <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
 <link href="https://fonts.googleapis.com/css2?family=JetBrains+Mono:wght@300;400;500;600;700&family=Orbitron:wght@400;500;600;700;800;900&display=swap" rel="stylesheet">
@@ -33,6 +40,11 @@
 </script>
 </head>
 <body>
+<!-- Offline Banner -->
+<div id="offline-banner" role="status" aria-live="polite">
+  ◈ NEXUS OFFLINE MODE — Running on cached assets
+</div>
+
 <!-- Loading Screen -->
 <div id="loading-screen">
  <div class="loader-content">
@@ -118,5 +130,23 @@
 </footer>

 <script type="module" src="./app.js"></script>
+<script>
+  // Offline/online detection
+  const offlineBanner = document.getElementById('offline-banner');
+  function updateOnlineStatus() {
+    offlineBanner.classList.toggle('visible', !navigator.onLine);
+  }
+  window.addEventListener('online', updateOnlineStatus);
+  window.addEventListener('offline', updateOnlineStatus);
+  updateOnlineStatus();
+
+  if ('serviceWorker' in navigator) {
+    window.addEventListener('load', () => {
+      navigator.serviceWorker.register('./sw.js')
+        .then(reg => console.log('[Nexus SW] Registered:', reg.scope))
+        .catch(err => console.warn('[Nexus SW] Registration failed:', err));
+    });
+  }
+</script>
 </body>
 </html>
--- a/manifest.json
+++ b/manifest.json
@@ -0,0 +1,25 @@
+{
+  "name": "The Nexus — Timmy's Sovereign Home",
+  "short_name": "The Nexus",
+  "description": "Timmy's sovereign 3D space. A crystalline hub outside time.",
+  "start_url": "/",
+  "display": "standalone",
+  "orientation": "landscape",
+  "background_color": "#050510",
+  "theme_color": "#4af0c0",
+  "categories": ["games", "entertainment"],
+  "icons": [
+    {
+      "src": "icons/icon-192.png",
+      "sizes": "192x192",
+      "type": "image/png",
+      "purpose": "any maskable"
+    },
+    {
+      "src": "icons/icon-512.png",
+      "sizes": "512x512",
+      "type": "image/png",
+      "purpose": "any maskable"
+    }
+  ]
+}
--- a/style.css
+++ b/style.css
@@ -359,3 +359,24 @@ canvas#nexus-canvas {
    display: none;
  }
 }
+
+/* === OFFLINE INDICATOR === */
+#offline-banner {
+  display: none;
+  position: fixed;
+  top: 0;
+  left: 0;
+  right: 0;
+  z-index: 1000;
+  padding: 6px 16px;
+  background: rgba(255, 170, 34, 0.15);
+  border-bottom: 1px solid var(--color-warning);
+  color: var(--color-warning);
+  font-family: var(--font-body);
+  font-size: var(--text-xs);
+  text-align: center;
+  letter-spacing: 0.08em;
+}
+#offline-banner.visible {
+  display: block;
+}
--- a/sw.js
+++ b/sw.js
@@ -0,0 +1,112 @@
+// ◈ The Nexus — Service Worker
+// Offline-first caching for sovereign space
+
+const CACHE_VERSION = 'nexus-v1';
+const STATIC_CACHE = `${CACHE_VERSION}-static`;
+const CDN_CACHE = `${CACHE_VERSION}-cdn`;
+
+// Core local assets — always cache
+const STATIC_ASSETS = [
+  '/',
+  '/index.html',
+  '/style.css',
+  '/app.js',
+  '/manifest.json',
+  '/icons/icon-192.png',
+  '/icons/icon-512.png',
+];
+
+// CDN assets for Three.js — cache on first fetch
+const CDN_ORIGINS = [
+  'https://cdn.jsdelivr.net',
+  'https://fonts.googleapis.com',
+  'https://fonts.gstatic.com',
+];
+
+// ═══ INSTALL — pre-cache static assets ═══
+self.addEventListener('install', event => {
+  event.waitUntil(
+    caches.open(STATIC_CACHE)
+      .then(cache => cache.addAll(STATIC_ASSETS))
+      .then(() => self.skipWaiting())
+  );
+});
+
+// ═══ ACTIVATE — clean up old caches ═══
+self.addEventListener('activate', event => {
+  event.waitUntil(
+    caches.keys()
+      .then(keys => Promise.all(
+        keys
+          .filter(key => key.startsWith('nexus-') && key !== STATIC_CACHE && key !== CDN_CACHE)
+          .map(key => caches.delete(key))
+      ))
+      .then(() => self.clients.claim())
+  );
+});
+
+// ═══ FETCH — serve from cache, fall back to network ═══
+self.addEventListener('fetch', event => {
+  const { request } = event;
+  const url = new URL(request.url);
+
+  // Skip non-GET requests
+  if (request.method !== 'GET') return;
+
+  // CDN resources: cache-first with network fallback
+  if (CDN_ORIGINS.some(origin => request.url.startsWith(origin))) {
+    event.respondWith(cdnFirst(request));
+    return;
+  }
+
+  // Same-origin static assets: cache-first
+  if (url.origin === self.location.origin) {
+    event.respondWith(staticFirst(request));
+    return;
+  }
+});
+
+// Cache-first for CDN (Three.js modules, fonts)
+async function cdnFirst(request) {
+  const cached = await caches.match(request);
+  if (cached) return cached;
+
+  try {
+    const response = await fetch(request);
+    if (response.ok) {
+      const cache = await caches.open(CDN_CACHE);
+      cache.put(request, response.clone());
+    }
+    return response;
+  } catch {
+    // Offline and not cached — return a minimal error response
+    return new Response('/* offline */', {
+      headers: { 'Content-Type': 'text/plain' },
+    });
+  }
+}
+
+// Cache-first for local static assets
+async function staticFirst(request) {
+  const cached = await caches.match(request);
+  if (cached) return cached;
+
+  try {
+    const response = await fetch(request);
+    if (response.ok) {
+      const cache = await caches.open(STATIC_CACHE);
+      cache.put(request, response.clone());
+    }
+    return response;
+  } catch {
+    // Offline fallback: serve index.html for navigation requests
+    if (request.mode === 'navigate') {
+      const fallback = await caches.match('/index.html');
+      if (fallback) return fallback;
+    }
+    return new Response('Nexus offline — cached assets not found.', {
+      status: 503,
+      headers: { 'Content-Type': 'text/plain' },
+    });
+  }
+}