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)

js/save.js

@@ -0,0 +1,100 @@
+'use strict';
+/* ============================================================
+   NEON SURVIVORS — save.js : localStorage persistence
+   Meta progression (gold, permanent upgrades, unlocks) + settings.
+   ============================================================ */
+
+const SAVE_KEY = 'neon_survivors_v1';
+
+const DEFAULT_SAVE = {
+  gold: 0,
+  meta: {},                 // metaId -> rank purchased
+  chars: ['kaito'],         // unlocked character ids
+  flags: { boss1: false, time10: false, time15: false },
+  totals: { kills: 0, gold: 0, best: 0, wins: 0, runs: 0, evos: 0, props: 0 },
+  progress: { stages: ['graveyard'], bestPerStage: {}, endlessBest: 0, stageWins: {}, gradeWins: {} },
+  skinOwned: {},            // 'charId:skinKey' -> 1
+  skinSel: {},              // charId -> skinKey
+  lbName: '',               // leaderboard display name
+  daily: { date: '', best: 0 },
+  ach: {},
+  history: [],
+  settings: {
+    lang: 'vi',
+    volMaster: 0.9,
+    volMusic: 0.6,
+    volSfx: 0.85,
+    shake: true,
+    dmgNum: true,
+    particles: 'high',      // low | med | high
+    fps: false,
+    autoPause: true,
+    dev: false,             // developer mode tools
+    keybinds: { up: 'KeyW', down: 'KeyS', left: 'KeyA', right: 'KeyD' }
+  }
+};
+
+const Store = {
+  data: null,
+
+  load() {
+    this.data = JSON.parse(JSON.stringify(DEFAULT_SAVE));
+    try {
+      const raw = localStorage.getItem(SAVE_KEY);
+      if (raw) {
+        const parsed = JSON.parse(raw);
+        // Deep-merge known sections so old saves survive schema additions.
+        for (const sec of ['flags', 'totals', 'settings', 'progress', 'daily', 'ach']) {
+          if (parsed[sec]) Object.assign(this.data[sec], parsed[sec]);
+        }
+        if (parsed.skinOwned) Object.assign(this.data.skinOwned, parsed.skinOwned);
+        if (parsed.skinSel) Object.assign(this.data.skinSel, parsed.skinSel);
+        if (!this.data.lbName && typeof parsed.lbName === 'string') this.data.lbName = parsed.lbName;
+        if (Array.isArray(parsed.history)) this.data.history = parsed.history.slice(0, 20);
+        if (typeof parsed.gold === 'number') this.data.gold = parsed.gold;
+        if (parsed.meta && typeof parsed.meta === 'object') this.data.meta = parsed.meta;
+        if (Array.isArray(parsed.chars)) this.data.chars = parsed.chars;
+      }
+    } catch (e) { console.warn('Save load failed', e); }
+    return this.data;
+  },
+
+  save() {
+    try { localStorage.setItem(SAVE_KEY, JSON.stringify(this.data)); }
+    catch (e) { console.warn('Save write failed', e); }
+  },
+
+  reset() {
+    this.data = JSON.parse(JSON.stringify(DEFAULT_SAVE));
+    this.save();
+  },
+
+  s() { return this.data.settings; },
+
+  addGold(n) {
+    this.data.gold += n;
+    this.data.totals.gold += Math.max(0, n);
+    // lazy-save; frequent small writes are cheap enough here
+    this.save();
+  },
+
+  spendGold(n) {
+    if (this.data.gold < n) return false;
+    this.data.gold -= n;
+    this.save();
+    return true;
+  },
+
+  rank(metaId) { return this.data.meta[metaId] || 0; },
+
+  unlockChar(id) {
+    if (!this.data.chars.includes(id)) {
+      this.data.chars.push(id);
+      this.save();
+      return true;
+    }
+    return false;
+  },
+
+  charUnlocked(id) { return this.data.chars.includes(id); }
+};