Satellite ground and real building footprints

- The ground is Esri World Imagery: ~1 m/pixel tiles around the city
  zone, the factory and 300 m either side of the drive between them,
  coarser tiles for the whole region. Tiles are hosted with the game
  (public/imagery, scripts/fetch-imagery.mjs), stream in near the camera,
  are cached by the service worker as visited, and replace the drawn
  roads and land areas
- ~141,500 Microsoft building footprints (ODbL) join OSM's ~4,000 in a
  compact delta-encoded file (public/data/buildings.bin, built by
  scripts/build-buildings.mjs). Heights are estimated from footprint
  area and land use, with industrial halls outside the ring road.
  Buildings are built in 500 m blocks as the camera approaches
- Caddy compresses the buildings file and caches map data for a week;
  the build targets ES2022 for top-level await
- Tests for decoding, factory clearance, machine reachability and tile
  placement

Imagery attribution: Esri, Maxar, Earthstar Geographics, and the GIS
User Community. Commercial use requires a suitable Esri licence.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

vite.config.js

@@ -10,21 +10,23 @@ const listFiles = dir => readdirSync(dir).flatMap(name => {
 
 // Emits sw.js listing every built file, so the installed game works offline. The cache name is a
 // hash of that list: a new build gets a new cache and the page offers to reload into it.
+// Satellite tiles (16 MB) are not precached; they are kept as the player passes them.
 function offlineServiceWorker() {
     return {
         name: 'offline-service-worker',
         apply: 'build',
         generateBundle(_, bundle) {
             const files = [...Object.keys(bundle), ...listFiles('public').map(f => relative('public', f).replaceAll('\\', '/'))]
-                .filter(f => f !== 'sw.js' && !f.endsWith('.map'));
+                .filter(f => f !== 'sw.js' && !f.endsWith('.map') && !(f.startsWith('imagery/') && f.endsWith('.jpg')));
             const version = createHash('sha1').update(files.join('\n')).digest('hex').slice(0, 12);
             this.emitFile({
                 type: 'asset', fileName: 'sw.js', source: `// Generated by vite.config.js — do not edit.
 const CACHE = 'robot-market-${version}';
+const TILES = 'robot-market-imagery';
 const FILES = ${JSON.stringify(['./', ...files.map(f => `./${f}`)])};
 self.addEventListener('install', event => event.waitUntil(caches.open(CACHE).then(cache => cache.addAll(FILES))));
 self.addEventListener('activate', event => event.waitUntil(caches.keys().then(keys =>
-    Promise.all(keys.filter(k => k.startsWith('robot-market-') && k !== CACHE).map(k => caches.delete(k)))).then(() => self.clients.claim())));
+    Promise.all(keys.filter(k => k.startsWith('robot-market-') && k !== CACHE && k !== TILES).map(k => caches.delete(k)))).then(() => self.clients.claim())));
 self.addEventListener('message', event => event.data === 'skip-waiting' && self.skipWaiting());
 self.addEventListener('fetch', event => {
     const request = event.request;
@@ -34,6 +36,14 @@ self.addEventListener('fetch', event => {
         event.respondWith(fetch(request).catch(() => caches.match('./')));
         return;
     }
+    // Satellite tiles: cache first, and keep each one fetched so visited areas work offline.
+    if (new URL(request.url).pathname.includes('/imagery/')) {
+        event.respondWith(caches.open(TILES).then(cache => cache.match(request).then(hit => hit ?? fetch(request).then(response => {
+            if (response.ok) cache.put(request, response.clone());
+            return response;
+        }))));
+        return;
+    }
     event.respondWith(caches.match(request, {ignoreSearch: true}).then(hit => hit ?? fetch(request)));
 });
 `
@@ -46,6 +56,8 @@ export default defineConfig({
     // Relative assets also load under a GitHub Pages repository path.
     base: './',
     plugins: [offlineServiceWorker()],
+    // Top-level await loads the building and imagery files before the world is built.
+    build: {target: 'es2022'},
     server: {
         host: true,
         allowedHosts: [