diff --git a/public/js/core/engine.js b/public/js/core/engine.js
new file mode 100644
index 0000000..ebb9916
--- /dev/null
+++ b/public/js/core/engine.js
@@ -0,0 +1,253 @@
+/* ============================================================
+   DSP ARCADE — shared core: engine, input, particles, highscores
+   ============================================================ */
+(function () {
+  'use strict';
+
+  // ---------- Canvas helpers ----------
+  function fitCanvas(canvas, w, h) {
+    canvas.width = w;
+    canvas.height = h;
+    const ctx = canvas.getContext('2d');
+    ctx.imageSmoothingEnabled = false;
+    return ctx;
+  }
+
+  // ---------- Input ----------
+  class Input {
+    constructor() {
+      this.keys = {};
+      this.pressed = {};
+      this.mouse = { x: 0, y: 0, down: false, clicked: false };
+      window.addEventListener('keydown', (e) => {
+        if (['ArrowUp','ArrowDown','ArrowLeft','ArrowRight','Space'].includes(e.code)) e.preventDefault();
+        if (!this.keys[e.code]) this.pressed[e.code] = true;
+        this.keys[e.code] = true;
+      });
+      window.addEventListener('keyup', (e) => { this.keys[e.code] = false; });
+      window.addEventListener('blur', () => { this.keys = {}; });
+      window.addEventListener('mousemove', (e) => {
+        this.mouse.x = e.clientX;
+        this.mouse.y = e.clientY;
+      });
+      window.addEventListener('mousedown', (e) => {
+        if (!this.mouse.down) this.mouse.clicked = true;
+        this.mouse.down = true;
+      });
+      window.addEventListener('mouseup', () => { this.mouse.down = false; });
+    }
+    canvasPos(canvas) {
+      const r = canvas.getBoundingClientRect();
+      return {
+        x: (this.mouse.x - r.left) * (canvas.width / r.width),
+        y: (this.mouse.y - r.top) * (canvas.height / r.height),
+      };
+    }
+    down(...codes) { return codes.some(c => this.keys[c]); }
+    wasPressed(...codes) { return codes.some(c => this.pressed[c]); }
+    mouseClicked() { return this.mouse.clicked; }
+    endFrame() { this.pressed = {}; this.mouse.clicked = false; }
+  }
+
+  // ---------- Particles ----------
+  class Particles {
+    constructor() { this.list = []; }
+    burst(x, y, color, n = 12, speed = 2.5, life = 30) {
+      for (let i = 0; i < n; i++) {
+        const a = Math.random() * Math.PI * 2;
+        const s = speed * (0.4 + Math.random() * 0.8);
+        this.list.push({ x, y, vx: Math.cos(a) * s, vy: Math.sin(a) * s, life, maxLife: life, color, size: 2 + Math.random() * 2 });
+      }
+    }
+    update() {
+      for (let i = this.list.length - 1; i >= 0; i--) {
+        const p = this.list[i];
+        p.x += p.vx; p.y += p.vy; p.vx *= 0.96; p.vy *= 0.96;
+        if (--p.life <= 0) this.list.splice(i, 1);
+      }
+    }
+    draw(ctx) {
+      for (const p of this.list) {
+        ctx.globalAlpha = p.life / p.maxLife;
+        ctx.fillStyle = p.color;
+        ctx.fillRect(p.x - p.size / 2, p.y - p.size / 2, p.size, p.size);
+      }
+      ctx.globalAlpha = 1;
+    }
+    clear() { this.list = []; }
+  }
+
+  // ---------- Screen shake ----------
+  class Shake {
+    constructor() { this.t = 0; this.mag = 0; }
+    trigger(mag, t) { this.mag = Math.max(this.mag, mag); this.t = Math.max(this.t, t); }
+    offset() {
+      if (this.t <= 0) return [0, 0];
+      this.t--;
+      const m = this.mag * (this.t / 20);
+      return [(Math.random() - 0.5) * 2 * m, (Math.random() - 0.5) * 2 * m];
+    }
+  }
+
+  // ---------- High scores ----------
+  const HighScores = {
+    key(game) { return 'dsp_hs_' + game; },
+    load(game) {
+      try { return JSON.parse(localStorage.getItem(this.key(game))) || []; }
+      catch { return []; }
+    },
+    save(game, list) {
+      localStorage.setItem(this.key(game), JSON.stringify(list.slice(0, 10)));
+    },
+    submit(game, score, name) {
+      const list = this.load(game);
+      list.push({ score, name: (name || '???').toUpperCase().slice(0, 8), date: Date.now() });
+      list.sort((a, b) => b.score - a.score);
+      const trimmed = list.slice(0, 10);
+      this.save(game, trimmed);
+      const rank = trimmed.findIndex(e => e.date === list.find(e => e.score === score && e.name === (name || '???').toUpperCase().slice(0, 8)).date);
+      return rank >= 0 ? rank + 1 : null;
+    },
+    best(game) { const l = this.load(game); return l.length ? l[0].score : 0; }
+  };
+
+  // ---------- Game state machine ----------
+  const STATE = { LOADING: 0, TITLE: 1, PLAYING: 2, PAUSED: 3, GAMEOVER: 4, HIGHSCORE: 5 };
+
+  // ---------- Base game ----------
+  class Game {
+    constructor(opts) {
+      this.name = opts.name;
+      this.title = opts.title;
+      this.W = opts.width; this.H = opts.height;
+      this.canvas = opts.canvas;
+      this.ctx = fitCanvas(this.canvas, this.W, this.H);
+      this.input = new Input();
+      this.particles = new Particles();
+      this.shake = new Shake();
+      this.state = STATE.LOADING;
+      this.score = 0;
+      this.lives = 3;
+      this.level = 1;
+      this.best = HighScores.best(this.name);
+      this.loadProgress = 0;
+      this.loadStep = 0;
+      this.loadSteps = opts.loadSteps || ['LOADING SPRITES', 'COMPILING WAVEFORMS', 'CHARGING REACTOR', 'SYNCING GRID'];
+      this.time = 0;
+      this.gameOverRank = null;
+      this.onGameOver = opts.onGameOver || null;
+      this._loop = this._loop.bind(this);
+      this._last = 0;
+      this._acc = 0;
+      this.step = 1000 / 60;
+      requestAnimationFrame(this._loop);
+    }
+    start() {
+      this.score = 0; this.lives = 3; this.level = 1;
+      this.particles.clear();
+      this.state = STATE.PLAYING;
+      this.reset();
+    }
+    reset() {}
+    update() {}
+    render() {}
+    _loop(ts) {
+      requestAnimationFrame(this._loop);
+      if (!this._last) this._last = ts;
+      let dt = ts - this._last;
+      this._last = ts;
+      if (dt > 100) dt = 100;
+      this._acc += dt;
+      while (this._acc >= this.step) {
+        this.tick();
+        this._acc -= this.step;
+      }
+      this.draw();
+      this.input.endFrame();
+    }
+    tick() {
+      this.time++;
+      switch (this.state) {
+        case STATE.LOADING:
+          this.loadProgress += 0.012 + Math.random() * 0.01;
+          const stepIdx = Math.floor(this.loadProgress * this.loadSteps.length);
+          if (stepIdx !== this.loadStep) this.loadStep = stepIdx;
+          if (this.loadProgress >= 1) { this.loadProgress = 1; this.state = STATE.TITLE; }
+          break;
+        case STATE.TITLE:
+          if (this.input.wasPressed('Space', 'Enter')) {
+            if (window.DSP_AUDIO) window.DSP_AUDIO.sfx('start');
+            this.start();
+          }
+          break;
+        case STATE.PLAYING:
+          if (this.input.wasPressed('KeyP')) { this.state = STATE.PAUSED; }
+          else if (this.input.wasPressed('Escape')) { this.onMouseCaptureRelease(); }
+          this.update();
+          this.particles.update();
+          break;
+        case STATE.PAUSED:
+          if (this.input.wasPressed('KeyP', 'Escape', 'Space')) this.state = STATE.PLAYING;
+          break;
+        case STATE.GAMEOVER:
+          this.particles.update();
+          if (this.input.wasPressed('Space', 'Enter')) {
+            if (this.gameOverRank === null) {
+              this.state = STATE.HIGHSCORE;
+            } else {
+              this.state = STATE.TITLE;
+            }
+          }
+          break;
+        case STATE.HIGHSCORE:
+          if (this.input.wasPressed('Enter')) {
+            const name = (this._hsName || 'AAA');
+            this.gameOverRank = HighScores.submit(this.name, this.score, name);
+            this.best = HighScores.best(this.name);
+            this.state = STATE.GAMEOVER;
+          }
+          break;
+      }
+    }
+    draw() {
+      const ctx = this.ctx;
+      const [sx, sy] = this.shake.offset();
+      ctx.save();
+      ctx.translate(sx, sy);
+      this.render();
+      ctx.restore();
+      this.particles.draw(ctx);
+      this.drawCRT(ctx);
+      this.drawOverlay(ctx);
+    }
+    drawCRT(ctx) {
+      ctx.globalAlpha = 0.08;
+      ctx.fillStyle = '#000';
+      for (let y = 0; y < this.H; y += 3) ctx.fillRect(0, y, this.W, 1);
+      ctx.globalAlpha = 1;
+      const g = ctx.createRadialGradient(this.W/2, this.H/2, this.H*0.45, this.W/2, this.H/2, this.H*0.85);
+      g.addColorStop(0, 'rgba(0,0,0,0)');
+      g.addColorStop(1, 'rgba(0,0,0,0.35)');
+      ctx.fillStyle = g;
+      ctx.fillRect(0, 0, this.W, this.H);
+    }
+    drawOverlay(ctx) {
+      if (window.DSP_UI) window.DSP_UI.draw(this);
+    }
+    gameOver() {
+      this.state = STATE.GAMEOVER;
+      this.shake.trigger(8, 30);
+      if (window.DSP_AUDIO) window.DSP_AUDIO.sfx('gameover');
+      if (this.score > 0 && this.score >= this.best) {
+        this.gameOverRank = null;
+      } else {
+        this.gameOverRank = -1;
+      }
+      if (this.onGameOver) this.onGameOver(this.score);
+    }
+    addScore(n) { this.score += n; }
+    onMouseCaptureRelease() {}
+  }
+
+  window.DSP = { Game, STATE, Input, Particles, Shake, HighScores, fitCanvas };
+})();
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