NEON SURVIVORS v1.1 — full-featured bullet-heaven survivor game

Vanilla JS + Canvas, zero dependencies, offline-first PWA.

Gameplay:
- 11 weapons x8 levels + 11 evolutions (chest-based), incl. timed mines
- 13 passives, crit system with directional hit-sparks & hit-stop
- 10 characters w/ unique mods + unlock conditions, gold cosmetic skins
- 3 biomes (Neon Graveyard / Frozen Hollow / Magma Rift) each with own
  spawn tables, boss plans and music flavor; Endless mode + surges;
  4 difficulty grades; breakable crystal-lamp props
- Elite random affixes (Swift/Sturdy/Volatile), 4 bosses, win flow
- Achievements (23) w/ gold rewards, run history, daily seeded challenge

Tech:
- Cinematic canvas main-menu scene, game-feel FX suite (trails, muzzle,
  status tints, low-HP pulse), viewport culling + particle pooling
- WebAudio synth SFX + generative per-biome soundtrack
- Gamepad support, remappable keys, touch joystick, fullscreen
- i18n VI/EN, localStorage saves w/ export-import codes
- Cloudflare Workers leaderboard scaffold (KV) w/ signed submits
- Headless integrity test-suite (node test/integrity.js)

manifest.webmanifest

@@ -0,0 +1,15 @@
+{
+  "name": "Neon Survivors — Bullet Heaven",
+  "short_name": "NeonSurv",
+  "description": "Sống sót giữa biển quái vật. Nâng cấp vũ khí. Tiến hóa. Hạ Tử Thần.",
+  "start_url": "./index.html",
+  "scope": "./",
+  "display": "fullscreen",
+  "orientation": "any",
+  "background_color": "#05050c",
+  "theme_color": "#7c5cff",
+  "icons": [
+    { "src": "icons/icon-192.png", "sizes": "192x192", "type": "image/png", "purpose": "any" },
+    { "src": "icons/icon-512.png", "sizes": "512x512", "type": "image/png", "purpose": "any maskable" }
+  ]
+}