Models 44

GPT-5 Nano

by OpenAIReasoningClean
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Running live in a sandboxed frame. Click inside it before using the keyboard.

How it went

Total time
1 min 44 s
Cost
$0.0054
Output tokens
13,446
Spent thinking
7,744 tokens
Speed
132.7 tok/s
Console errors
0
First token after
3.0 s
First visible text after
1 min 21 s
Prompt tokens
493
Code size
18.5 KB
Finish reason
stop
Served by
OpenAI
Model id
openai/gpt-5-nano
Reasoning sent
model default
Max output
128,000 tokens
Generated
Nov 12, 2026

What it was asked

The prompt
Build a polished Snake game in a single HTML file using vanilla JavaScript and a <canvas>. Requirements: - A grid of at least 20×20 cells, centered on the page. - Arrow keys and WASD control the snake. Quick successive key presses must both be honored, but the snake can never reverse onto itself. - Eating food adds 10 points and grows the snake by one cell; new food never spawns on the snake. - Game over when the snake hits a wall or itself, with an overlay showing the score; Space or Enter restarts, P pauses. - Visual polish: smooth movement, a snake with a distinct head and eyes facing its direction, and a small particle burst when eating. - Display the current score and the best score of the session.
System prompt, sent with every prompt
You are generating a self-contained web demo. It will be rendered automatically in a sandboxed iframe and compared side by side with the output of other AI models given the exact same task.

Output rules:
- Reply with exactly ONE fenced code block containing the complete file: ```html (or ```svg when the task asks for an SVG). No text before or after the code block.
- Everything must be inline: CSS in <style>, JavaScript in <script>. No external files, images, fonts or network requests, except the CDN URLs explicitly allowed by the task.
- Do not use localStorage, sessionStorage, cookies, IndexedDB, alert(), confirm(), prompt() or window.open(): they are blocked in the sandbox and will throw.
- The page must look right in a 1280×800 viewport and adapt gracefully down to 375px wide. No horizontal scrollbar.
- Something meaningful must be visible on first paint: a screenshot is taken automatically about 3 seconds after load, without any interaction.
- Everything that makes the demo interesting must be visible within the first seconds: nothing hidden behind a high score, a later level or a long play session.
- Games must start in a self-playing demo mode (a simple AI plays) behind a "Click or press a key to start" message, so the game can be judged in action without playing.
- The iframe only receives keyboard events after the user clicks it: if the demo uses the keyboard, display a clear "Click or press a key to start" message.
- The code must run with zero errors in the console of the latest Chrome.

Code run-1.html · 666 lines

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <title>Snake — Self-Playing Demo (Vanilla JS, Canvas)</title>
  <meta name="viewport" content="width=device-width, initial-scale=1" />
  <style>
    :root {
      --bg: #0e111a;
      --panel: #171c26;
      --snake: #43d76b;
      --snakeHead: #2a9d42;
      --food: #e74c3c;
      --grid: rgba(255,255,255,0.08);
      --text: #eaeef6;
      --textDim: rgba(234,238,246,0.6);
      --overlay: rgba(0,0,0,0.6);
      --shadow: 0 6px 20px rgba(0,0,0,.25);
    }

    * { box-sizing: border-box; }
    html, body { height: 100%; margin: 0; background: radial-gradient( circle at 50% 20%, rgba(60,60,120,.25), rgba(0,0,0,0) 40%), var(--bg); color: white; font-family: Inter, system-ui, -apple-system, "Segoe UI", Roboto, Arial; }

    /* Center the demo on the page, responsive from 1280x800 down to 375px */
    .stage {
      height: 100vh;
      display: grid;
      place-items: center;
      padding: 20px;
    }

    .panel {
      width: min(92vmin, 980px);
      aspect-ratio: 1.33; /* roughly 4:3 to keep grid pleasant on 1280x800 */
      min-width: 320px;
      display: grid;
      grid-template-rows: auto 1fr auto;
      gap: 10px;
      align-items: center;
      justify-items: center;
      padding: 14px;
      border-radius: 16px;
      background: linear-gradient(180deg, rgba(20,26,32,.95), rgba(14,18,26,.92));
      box-shadow: var(--shadow);
      border: 1px solid rgba(255,255,255,.08);
    }

    #hud {
      width: 100%;
      display: flex;
      justify-content: space-between;
      align-items: center;
      padding: 6px 12px;
      font-size: 14px;
      color: var(--textDim);
      user-select: none;
    }

    #hud .badge {
      padding: 6px 10px;
      border-radius: 999px;
      background: rgba(0,0,0,.25);
      border: 1px solid rgba(255,255,255,.08);
      color: #e9f7ff;
    }

    canvas {
      width: 100%;
      height: 100%;
      display: block;
      image-rendering: crisp-edges;
      background: #0b1020;
      border-radius: 12px;
      outline: none;
    }

    /* Overlays */
    .overlay {
      position: fixed;
      inset: 0;
      display: none;
      align-items: center;
      justify-content: center;
      text-align: center;
      padding: 20px;
      background: var(--overlay);
      z-index: 10;
      cursor: default;
      user-select: none;
      color: #fff;
    }
    .overlay.active { display: flex; }

    .overlay .card {
      background: rgba(20, 25, 34, 0.92);
      padding: 28px 28px;
      border-radius: 14px;
      border: 1px solid rgba(255,255,255,.08);
      max-width: 90vw;
      box-shadow: 0 8px 28px rgba(0,0,0,.4);
    }

    .overlay h1 {
      margin: 0 0 8px 0;
      font-size: 22px;
      letter-spacing: .4px;
    }

    .overlay p {
      margin: 6px 0 0;
      color: var(--textDim);
      font-size: 14px;
    }

    /* Start prompt micro-UI cue */
    #startHint {
      margin-top: 6px;
      font-size: 12px;
      color: var(--textDim);
      opacity: 0.9;
    }

    @media (max-width: 700px) {
      .panel { aspect-ratio: auto; width: 100%; }
      #hud { font-size: 13px; padding: 4px 8px; }
    }
  </style>
</head>
<body>
  <div class="stage" aria-label="Snake game stage">
    <div class="panel" id="panel">
      <div id="hud" aria-label="Score HUD">
        <div>Score: <span id="score">0</span></div>
        <div>Best: <span id="best">0</span></div>
      </div>
      <canvas id="canvas" width="640" height="520" tabindex="0" aria-label="Snake canvas"></canvas>
      <div id="startHint" style="opacity:.75; text-align:center;">Click the canvas to start • Use Arrow keys or WASD to move</div>
    </div>
  </div>

  <!-- Overlays -->
  <div id="overlayStart" class="overlay active" aria-hidden="false">
    <div class="card" role="dialog" aria-label="Start dialog">
      <h1>Snake — Demo Mode</h1>
      <p>Watch a simple AI play the game. Click or press any key to start controlling the snake yourself.</p>
      <div id="startHint" style="margin-top:6px;">Click anywhere on the canvas or press a key to begin</div>
    </div>
  </div>

  <div id="overlayPause" class="overlay" aria-hidden="true">
    <div class="card">
      <h1>Paused</h1>
      <p>Press P to resume. Score: <span id="pauseScore">0</span></p>
      <p>Best: <span id="pauseBest">0</span></p>
    </div>
  </div>

  <div id="overlayOver" class="overlay" aria-hidden="true">
    <div class="card">
      <h1>Game Over</h1>
      <p>Score: <span id="finalScore">0</span> • Best: <span id="finalBest">0</span></p>
      <p>Press Space or Enter to restart</p>
    </div>
  </div>

  <script>
  // Snake — Vanilla JS + Canvas
  // Grid dimensions (at least 20x20)
  const GRID_W = 24;
  const GRID_H = 24;

  // Canvas and rendering
  const canvas = document.getElementById('canvas');
  const ctx = canvas.getContext('2d');
  let cellSize = 20; // will be recalculated on resize
  let widthPx = GRID_W * cellSize;
  let heightPx = GRID_H * cellSize;
  canvas.width = widthPx;
  canvas.height = heightPx;

  // Game state
  let snake = [];
  let dir = { x: 1, y: 0 };
  let nextDirQueue = [];
  let food = { x: 0, y: 0 };
  let score = 0;
  let bestScore = 0;
  let started = false;
  let paused = false;
  let gameOver = false;

  // UI
  const scoreSpan = document.getElementById('score');
  const bestSpan = document.getElementById('best');
  const finalScoreSpan = document.getElementById('finalScore');
  const finalBestSpan = document.getElementById('finalBest');
  const pauseScoreSpan = document.getElementById('pauseScore');
  const pauseBestSpan = document.getElementById('pauseBest');
  const overlayStart = document.getElementById('overlayStart');
  const overlayPause = document.getElementById('overlayPause');
  const overlayOver = document.getElementById('overlayOver');
  const startHint = document.getElementById('startHint');

  // Particles for eat burst
  const particles = [];

  // Timing
  const TICK = 100; // ms per move
  let lastTime = 0;
  let acc = 0;
  let allowKeys = false; // keyboard enabled after start

  // Init
  function randInt(n) { return Math.floor(Math.random() * n); }

  function spawnFood() {
    // pick a random cell not occupied by the snake
    let tries = 0;
    const maxTries = GRID_W * GRID_H * 2;
    while (tries < maxTries) {
      const x = randInt(GRID_W);
      const y = randInt(GRID_H);
      if (!snake.some(s => s.x === x && s.y === y)) {
        food.x = x;
        food.y = y;
        return;
      }
      tries++;
    }
    // fallback (shouldn't happen)
    for (let x = 0; x < GRID_W; x++) {
      for (let y = 0; y < GRID_H; y++) {
        if (!snake.some(s => s.x === x && s.y === y)) {
          food.x = x; food.y = y;
          return;
        }
      }
    }
  }

  function resetGame() {
    snake = [];
    const midX = Math.floor(GRID_W / 2);
    const midY = Math.floor(GRID_H / 2);
    snake.push({ x: midX, y: midY });
    snake.push({ x: midX - 1, y: midY });
    snake.push({ x: midX - 2, y: midY });
    dir = { x: 1, y: 0 };
    nextDirQueue = [];
    score = 0;
    started = false;
    paused = false;
    gameOver = false;
    spawnFood();
    updateHUD();
  }

  function updateHUD() {
    scoreSpan.textContent = score.toString();
    bestSpan.textContent = bestScore.toString();
  }

  function overlayToggle(overlay, show) {
    if (show) {
      overlay.classList.add('active');
      overlay.setAttribute('aria-hidden', 'false');
    } else {
      overlay.classList.remove('active');
      overlay.setAttribute('aria-hidden', 'true');
    }
  }

  function startGame() {
    if (gameOver) {
      restartGame();
      return;
    }
    started = true;
    paused = false;
    allowKeys = true;
    overlayToggle(overlayStart, false);
  }

  function restartGame() {
    resetGame();
    overlayToggle(overlayOver, false);
    overlayToggle(overlayPause, false);
    // Start fresh with AI demo for initial steps, keyboard will take over on first input
  }

  // Simple collision check: is (x,y) inside grid
  function inBounds(x, y) {
    return x >= 0 && x < GRID_W && y >= 0 && y < GRID_H;
  }

  // Is position safe from collision with body, considering tail may move
  function isSafePosition(x, y) {
    if (!inBounds(x, y)) return false;
    // If the position equals any body segment, treat as unsafe
    for (let i = 0; i < snake.length; i++) {
      if (snake[i].x === x && snake[i].y === y) {
        // allow stepping into current tail (will move away unless we just ate)
        // It's safe to allow at tail index if it's about to vacate
        return i === snake.length - 1;
      }
    }
    return true;
  }

  // AI decision for demo mode (not controlling after start)
  function aiDecision() {
    if (started) return;
    // If queue already has a candidate, do not override
    if (nextDirQueue.length > 0) return;
    const head = snake[0];
    const candidates = [
      { x: 1, y: 0 }, // right
      { x: -1, y: 0 }, // left
      { x: 0, y: 1 }, // down
      { x: 0, y: -1 } // up
    ];
    // Prefer direction that reduces manhattan distance to food
    const dists = candidates.map(c => {
      const nx = head.x + c.x;
      const ny = head.y + c.y;
      const dist = Math.abs(food.x - nx) + Math.abs(food.y - ny);
      return { c, dist, nx, ny };
    });
    // Filter safe moves
    const safe = dists.filter(d => isSafePosition(d.nx, d.ny));
    if (safe.length > 0) {
      safe.sort((a, b) => a.dist - b.dist);
      nextDirQueue.push({ x: safe[0].c.x, y: safe[0].c.y });
      return;
    }
    // If no safe move according to food distance, pick any non-opposite safe move
    for (let c of candidates) {
      if (c.x === -dir.x && c.y === -dir.y) continue; // don't reverse
      if (isSafePosition(head.x + c.x, head.y + c.y)) {
        nextDirQueue.push({ x: c.x, y: c.y });
        return;
      }
    }
  }

  // Resize / adapt canvas to fit viewport while preserving grid
  function resize() {
    const panel = document.getElementById('panel');
    // Desired cell size based on available space
    const padding = 40;
    const maxW = panel.clientWidth - padding * 0.5;
    const maxH = panel.clientHeight - 80;
    const best = Math.min(
      Math.floor(maxW / GRID_W),
      Math.floor(maxH / GRID_H),
      32 // cap for readability
    );
    cellSize = Math.max(12, best);
    widthPx = GRID_W * cellSize;
    heightPx = GRID_H * cellSize;
    canvas.style.width = widthPx + 'px';
    canvas.style.height = heightPx + 'px';
    canvas.width = GRID_W * cellSize;
    canvas.height = GRID_H * cellSize;
  }

  // Rendering
  function renderGridBackground() {
    // subtle checker/grid background
    ctx.fillStyle = '#0b1020';
    ctx.fillRect(0, 0, canvas.width, canvas.height);
    // optional grid lines
    ctx.strokeStyle = 'rgba(255,255,255,0.05)';
    ctx.lineWidth = 1;
    for (let x = 0; x <= GRID_W; x++) {
      const X = x * cellSize;
      ctx.beginPath();
      ctx.moveTo(X + 0.5, 0);
      ctx.lineTo(X + 0.5, canvas.height);
      ctx.stroke();
    }
    for (let y = 0; y <= GRID_H; y++) {
      const Y = y * cellSize;
      ctx.beginPath();
      ctx.moveTo(0, Y + 0.5);
      ctx.lineTo(canvas.width, Y + 0.5);
      ctx.stroke();
    }
  }

  function drawSnake() {
    for (let i = 0; i < snake.length; i++) {
      const s = snake[i];
      const x = s.x * cellSize;
      const y = s.y * cellSize;
      ctx.fillStyle = i === 0 ? '#2a9d42' : '#43d76b';
      ctx.fillRect(x + 2, y + 2, cellSize - 4, cellSize - 4);
    }
    // head eyes facing its direction
    if (snake.length > 0) {
      const head = snake[0];
      const cx = head.x * cellSize;
      const cy = head.y * cellSize;
      const dirX = dir.x;
      const dirY = dir.y;
      // center of head
      const headCx = cx + cellSize / 2;
      const headCy = cy + cellSize / 2;
      // determine eye positions near the front
      let frontX = headCx;
      let frontY = headCy;
      frontX += dirX * (cellSize * 0.25);
      frontY += dirY * (cellSize * 0.25);
      let perpX = 0, perpY = 0;
      if (dirX !== 0) { perpY = cellSize * 0.18; }
      if (dirY !== 0) { perpX = cellSize * 0.18; }
      const eye1X = frontX - perpX;
      const eye1Y = frontY - perpY;
      const eye2X = frontX + perpX;
      const eye2Y = frontY + perpY;
      ctx.fillStyle = '#111';
      ctx.beginPath();
      ctx.arc(eye1X, eye1Y, Math.max(1.5, cellSize * 0.08), 0, Math.PI * 2);
      ctx.arc(eye2X, eye2Y, Math.max(1.5, cellSize * 0.08), 0, Math.PI * 2);
      ctx.fill();
    }
  }

  function drawFood() {
    const x = food.x * cellSize;
    const y = food.y * cellSize;
    ctx.fillStyle = '#e74c3c';
    ctx.beginPath();
    ctx.arc(x + cellSize / 2, y + cellSize / 2, Math.max(4, cellSize * 0.28), 0, Math.PI * 2);
    ctx.fill();
  }

  function drawParticles(dt) {
    // update particle states
    for (let i = particles.length - 1; i >= 0; i--) {
      const p = particles[i];
      p.x += p.vx * (cellSize * 0.12);
      p.y += p.vy * (cellSize * 0.12);
      p.life -= dt;
      if (p.life <= 0) {
        particles.splice(i, 1);
      } else {
        ctx.fillStyle = p.color;
        ctx.globalAlpha = Math.max(0, p.life / p.maxLife);
        ctx.fillRect((p.x) * cellSize - 1, (p.y) * cellSize - 1, 2, 2);
        ctx.globalAlpha = 1;
      }
    }
  }

  function spawnEatBurst(headX, headY) {
    // center at the head cell
    for (let i = 0; i < 14; i++) {
      const ang = (i / 14) * Math.PI * 2;
      const speed = 0.6 + Math.random() * 0.6;
      const vx = Math.cos(ang) * speed;
      const vy = Math.sin(ang) * speed;
      particles.push({
        x: headX + 0.5,
        y: headY + 0.5,
        vx, vy,
        life: 0.9,
        maxLife: 0.9,
        color: 'rgba(255, 240, 110, 1)'
      });
    }
  }

  function render(dt) {
    renderGridBackground();
    // draw in proper order
    drawFood();
    drawSnake();
    drawParticles(dt);
  }

  // Game loop
  function loop(ts) {
    if (!lastTime) lastTime = ts;
    const dt = Math.min(0.032, (ts - lastTime) / 1000);
    lastTime = ts;

    // Demo AI drives before user starts
    if (!started && !gameOver) {
      aiDecision();
    }

    // Move if not paused, not game over
    if (!paused && started && !gameOver) {
      acc += dt * 1000; // convert to ms for tick rhythm
      while (acc >= TICK) {
        stepGame();
        acc -= TICK;
      }
    } else {
      // Even when paused or not started, render with slight pause
    }

    render(dt);
    requestAnimationFrame(loop);
  }

  function stepGame() {
    // Apply queued directions (honor quick successive inputs)
    if (nextDirQueue.length > 0) {
      // take the first candidate that isn't reversing
      let applied = false;
      while (nextDirQueue.length > 0) {
        const cand = nextDirQueue.shift();
        if (cand.x !== -dir.x || cand.y !== -dir.y) {
          dir = { x: cand.x, y: cand.y };
          applied = true;
          break;
        }
      }
      // if none applicable, keep current dir
      if (!applied) nextDirQueue = [];
    }

    const nx = snake[0].x + dir.x;
    const ny = snake[0].y + dir.y;

    // Wall or self collision
    if (!inBounds(nx, ny) || snake.some((s, idx) => idx > -1 && s.x === nx && s.y === ny)) {
      gameOver = true;
      overlayOverScore();
      overlayToggle(overlayOver, true);
      overlayToggle(overlayPause, false);
      started = false;
      // pause keyboards until restart
      allowKeys = false;
      // Update final score
      finalScoreSpan.textContent = score.toString();
      finalBestSpan.textContent = bestScore.toString();
      pauseScoreSpan.textContent = score.toString();
      pauseBestSpan.textContent = bestScore.toString();
      return;
    }

    // Move
    snake.unshift({ x: nx, y: ny });

    // Food check
    const ate = (nx === food.x && ny === food.y);
    if (ate) {
      score += 10;
      if (score > bestScore) bestScore = score;
      updateHUD();
      spawnFood();
      // burst particles at eat location
      spawnEatBurst(nx, ny);
    } else {
      // normal move: remove tail
      snake.pop();
    }

    // After moving, if not started by user, the AI can keep queueing
    if (!started) {
      // continue to push a direction toward food if possible
      aiDecision();
    }
  }

  function overlayOverScore() {
    finalScoreSpan.textContent = score.toString();
    finalBestSpan.textContent = Math.max(bestScore, score).toString();
  }

  // Input handling
  function onKeyDown(e) {
    // Start and pause controls
    if (!allowKeys) {
      // If still in startup phase, any key will start after clicking overlay
      return;
    }
    // Map keys
    const key = e.key.toLowerCase();
    // Directions
    const map = {
      'arrowleft': { x: -1, y: 0 },
      'arrowright': { x: 1, y: 0 },
      'arrowup': { x: 0, y: -1 },
      'arrowdown': { x: 0, y: 1 },
      'a': { x: -1, y: 0 },
      'd': { x: 1, y: 0 },
      'w': { x: 0, y: -1 },
      's': { x: 0, y: 1 }
    };
    if (map[key]) {
      // Enqueue direction vector
      nextDirQueue.push({ x: map[key].x, y: map[key].y });
      e.preventDefault();
    } else if (key === 'p') {
      // Pause toggle
      if (gameOver) return;
      paused = !paused;
      overlayToggle(overlayPause, paused);
      // update pause overlay numbers
      if (paused) {
        pauseScoreSpan.textContent = score.toString();
        pauseBestSpan.textContent = bestScore.toString();
      }
    } else if (key === ' ' || key === 'space') {
      // Space restarts if game over
      if (gameOver) {
        restartGame();
        overlayToggle(overlayOver, false);
      }
      e.preventDefault();
    } else if (key === 'enter') {
      if (gameOver) {
        restartGame();
        overlayToggle(overlayOver, false);
      }
      e.preventDefault();
    }
  }

  // Mouse / click to start
  canvas.addEventListener('mousedown', () => {
    if (!started && !gameOver) {
      started = true;
      allowKeys = true;
      overlayToggle(overlayStart, false);
    } else if (!started && gameOver) {
      // clicking after game over restarts too
      restartGame();
      overlayToggle(overlayOver, false);
      overlayToggle(overlayStart, true);
    }
  });

  // Prevent accidental scrolling with arrow keys when focused
  window.addEventListener('keydown', onKeyDown);

  // Resize handling
  window.addEventListener('resize', resize);

  // Initialize
  resetGame();
  resize();
  // Start the animation loop
  requestAnimationFrame(loop);
  // Ensure the best score starts at 0 for session
  bestScore = 0;
  updateHUD();

  // For accessibility: click hint message disappears when user starts
  overlayStart.addEventListener('click', () => {
    if (!started) {
      startGame();
    }
  });

  // Activate the start overlay initially
  overlayToggle(overlayStart, true);
  // Sync HUD on initial render
  updateHUD();
  </script>
</body>
</html>
Reasoning trace (7,744 tokens)
**Designing a Snake Game**

I need to create a single HTML file that includes all inline CSS and JavaScript for a self-contained Snake game. The game will use a grid of at least 20x20, possibly expanding to 25x25, and will be centered on the page. Controls will include the Arrow keys and WASD. I’ll implement a direction queue to handle rapid key presses while ensuring the snake doesn’t reverse. The nextDirection variable will help manage changes unless it contradicts the current direction. If multiple keys are pressed, I’ll queue them and apply each direction at every tick.**Implementing Direction Logic**

I want to follow a standard approach for capturing input by setting the pendingDirection based on what the user pressed. However, if multiple keys are pressed, only the latest should be recorded as lastDirection. The phrase "both be honored" suggests that quick rotations could allow multiple direction changes between frame updates. I'll create a direction queue of, say, three directions. At each tick, I'll apply the first direction that isn't opposite to the current one, ensuring all key presses are honored effectively. Alternatively, I could simplify by pushing keys directly into the queue.**Defining Game Mechanics**

I need to ensure that the snake doesn’t reverse by checking that the next direction isn’t opposite to the currentDirection. I’ll implement the game loop using requestAnimationFrame with a fixed tick rate of 10 ticks per second. To control movement, I'll use a time accumulator to advance the snake every specified interval. The snake will be represented as an array of segments, with coordinates on a grid of 22x22 or 25x25. The canvas will adjust to fit the window, and I’ll ensure the grid is centered on the page. Food will spawn randomly, and the score will start at zero, increasing by 10 with each food item collected. I'll also track the best score for the session without using localStorage.**Implementing Game Features**

To track the best score of the session, I’ll use a variable called bestScore that persists throughout the session but resets upon page reload. I’ll create an overlay for the game over screen that displays both the current score and the best score, along with instructions for restarting or pausing the game. The game will initially present an overlay message that prompts players to start by clicking or pressing a key. In demo mode, an AI snake will automatically move until the user input begins, allowing for a self-playing experience before transitioning to user control. The user will also have the option to pause and resume the game.**Finalizing Game Implementation**

I need to implement control instructions, where Space or Enter restarts the game, and P pauses it. The initial state will feature an AI-controlled snake that plays automatically until the user starts the game. The overlay will prompt users to click or press a key to initiate play. After starting, the AI will continue to guide the snake, and user inputs will then control its direction. I’ll also handle game mechanics such as food spawning, collision detection, score tracking, and visual enhancements like smooth movement and particle effects. Ensuring everything is responsive and visually appealing across different devices is key, while maintaining no errors in the console. The best score will persist across restarts in the session.**Implementing Game Logic and Controls**

To prevent collisions, the AI will choose a safe direction each tick if the game is not started or paused, especially in demo mode. The game will feature overlays for start, pause, and game over states. Pressing Space or Enter will restart the game only when the game over overlay is visible, while P will toggle the pause state during play.

For the data structures, I’ll define the grid size and snake segments, track scores, and manage the game status with variables. I’ll implement a simple renderer using canvas context, ensuring everything draws correctly, including the snake and food. 

The collision checks will determine if the snake collides with the wall or itself, causing the game to end. The movement will handle food consumption and particle bursts upon eating, enhancing the visual experience. The direction queue will allow handling of multiple key presses efficiently, ensuring quick changes in snake movement while avoiding reversals.**Refining the AI Movement Logic**

I need to ensure that the snake never reverses onto itself. I’ll start with an initial direction of {1,0} and a short starting position. When spawning food, I’ll check that it doesn't appear on the snake’s body. 

The AI will operate when the game is not started or paused, calculating how to move towards the food without self-collision or running into walls. I’ll create a function to prioritize safe movements while pushing candidates into the direction queue efficiently. 

I’ll implement overlays for starting, pausing, and game over states, ensuring the UI is user-friendly and responsive across various screen sizes. Finally, I’ll manage the HTML layout with a CSS-based approach for flexibility and clarity.**Implementing Responsive Features**

I need to make my game responsive. I’ll create a `resize()` function to adjust the cell size based on the window's dimensions, ensuring it doesn’t drop below 12 pixels. 

The canvas should be centered, and I want to eliminate horizontal scrollbars by controlling overflow. I’ll also incorporate score tracking into the display. For the snake's head, I aim to add small eyes that change depending on direction. 

Additionally, I’ll develop an AI that adjusts based on proximity to food, while ensuring safety checks for movements to prevent collisions. I'll take it step by step to ensure clarity and functionality.**Refining AI Move Logic**

In AI movement, I need to consider that the snake might not grow immediately after eating, so I have to allow for the tail in collision checks. The AI's decision-making will happen before the snake moves, meaning new head calculations will keep the game flowing smoothly, even in demo mode where user control isn't present. 

Finally, I’ll ensure the visual rendering, including drawing the snake and its eyes, is efficient and engaging, focusing on the head's orientation and direction through carefully positioned small circles.**Implementing Particle Effects and Overlay**

I'll set up the snake's eyes based on its direction using offsets that are perpendicular. For the eyes, I’ll position them slightly off from the head's front, using small squares to represent them.

In rendering particles, I plan to update each one based on its velocity and life. I'll also implement an overlay instruction that prompts the user to click or press a key to start the game. This will involve adding event listeners while ensuring keyboard events are only registered after user interaction. It’s important to handle this smoothly and debug thoroughly as I go.