Make this code better in one html file. Improve the game: <!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <meta
    name="viewport"
    content="width=device-width,initial-scale=1,user-scalable=no,viewport-fit=cover"
  />
  <title>Cyber-Neon Snake</title>
  <style>
    /* Reset & Base */
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }
    html, body {
      height: 100%;
      overflow: hidden;
      user-select: none;
      background: linear-gradient(45deg, #0f2027, #203a43, #2c5364);
      background-size: 600% 600%;
      animation: bgShift 20s ease infinite;
      font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      color: #0f9;
    }
    @keyframes bgShift {
      0% { background-position: 0% 50%; }
      50% { background-position: 100% 50%; }
      100% { background-position: 0% 50%; }
    }

    /* Game Frame */
    #game {
      position: relative;
      width: 90vmin;
      height: 90vmin;
      background: #111;
      border: 4px solid #0f9;
      border-radius: 20px;
      box-shadow: inset 0 0 20px #0f9a;
      touch-action: none;
      user-select: none;
    }
    canvas {
      width: 100%;
      height: 100%;
      display: block;
      background: #111;
      border-radius: 20px;
    }

    /* Neon Scoreboard */
    @keyframes neonFlicker {
      0%, 18%, 22%, 25%, 53%, 57%, 100% {
        text-shadow:
          0 0 5px #0f9,
          0 0 10px #0f9,
          0 0 20px #0f9,
          0 0 40px #0ff,
          0 0 80px #0ff;
      }
      20%, 24%, 55% {
        text-shadow: none;
      }
    }
    #scoreboard {
      margin-top: 12px;
      text-align: center;
      font-size: 1.5rem;
      font-weight: 700;
      animation: neonFlicker 3s infinite;
      user-select: none;
    }
    #scoreboard.flash {
      color: #fff;
      text-shadow:
        0 0 25px #0ff,
        0 0 50px #0ff,
        0 0 75px #0ff;
      transition: text-shadow 0.2s, color 0.2s;
    }

    /* Controls */
    #controls {
      margin-top: 12px;
      display: grid;
      grid-template-columns: repeat(4, 1fr);
      gap: 12px;
      width: 90vmin;
      max-width: 400px;
    }
    .btn {
      background: #0f9;
      border: none;
      border-radius: 12px;
      padding: 14px 0;
      font-size: 1.4rem;
      font-weight: 700;
      box-shadow: 0 0 20px #0f9;
      cursor: pointer;
      transition: background 0.2s, box-shadow 0.2s, transform 0.1s;
      user-select: none;
      color: #000;
      outline-offset: 2px;
      outline-color: transparent;
      outline-style: solid;
    }
    .btn:hover,
    .btn:focus-visible {
      background: #0cffaa;
      box-shadow: 0 0 30px #0cffaa;
      outline-color: #0cffaa;
      transform: scale(1.05);
    }
    .btn:active {
      background: #0c7;
      box-shadow: inset 0 0 30px #0c7;
      transform: scale(0.95);
    }
    @media (max-width: 400px) {
      .btn {
        font-size: 1.2rem;
        padding: 10px 0;
      }
    }

    /* Pause and Restart Buttons */
    #pauseBtn, #restartBtn {
      margin-top: 12px;
      background: #0f9;
      border: none;
      border-radius: 12px;
      padding: 12px 0;
      font-size: 1.3rem;
      font-weight: 700;
      box-shadow: 0 0 20px #0f9;
      cursor: pointer;
      user-select: none;
      width: 90vmin;
      max-width: 400px;
      transition: background 0.2s, box-shadow 0.2s, transform 0.1s;
      color: #000;
    }
    #pauseBtn:hover, #pauseBtn:focus-visible,
    #restartBtn:hover, #restartBtn:focus-visible {
      background: #0cffaa;
      box-shadow: 0 0 30px #0cffaa;
      transform: scale(1.05);
    }
    #pauseBtn:active, #restartBtn:active {
      background: #0c7;
      box-shadow: inset 0 0 30px #0c7;
      transform: scale(0.95);
    }
    #restartBtn {
      background: #0ff;
      box-shadow: 0 0 25px #0ff;
      display: none;
    }
    #restartBtn:hover, #restartBtn:focus-visible {
      background: #0cc;
      box-shadow: 0 0 40px #0cc;
    }
    #restartBtn:active {
      background: #099;
      box-shadow: inset 0 0 30px #099;
    }
  </style>
</head>
<body>
  <div id="game" role="region" aria-label="Snake game area">
    <canvas id="canvas" tabindex="0" aria-live="polite" aria-label="Game canvas"></canvas>
  </div>

  <div id="controls" aria-label="Directional controls">
    <button class="btn" data-dir="left" aria-label="Move left" type="button">←</button>
    <button class="btn" data-dir="up" aria-label="Move up" type="button">↑</button>
    <button class="btn" data-dir="down" aria-label="Move down" type="button">↓</button>
    <button class="btn" data-dir="right" aria-label="Move right" type="button">→</button>
  </div>

  <div id="scoreboard" aria-live="polite" aria-atomic="true" role="status">
    Score: <span id="currentScore">0</span> | High: <span id="highScore">0</span>
  </div>

  <button id="pauseBtn" type="button" aria-label="Pause game">Pause</button>
  <button id="restartBtn" type="button" aria-label="Restart game">Restart Game</button>

  <audio id="eatSfx" src="eat.mp3" preload="auto" aria-hidden="true"></audio>

  <script>
  (function(){
    // DOM & Audio References
    const game       = document.getElementById('game');
    const canvas     = document.getElementById('canvas');
    const ctx        = canvas.getContext('2d');
    const scoreEl    = document.getElementById('currentScore');
    const highEl     = document.getElementById('highScore');
    const sb         = document.getElementById('scoreboard');
    const eatSfx     = document.getElementById('eatSfx');
    const btns       = document.querySelectorAll('.btn');
    const pauseBtn   = document.getElementById('pauseBtn');
    const restartBtn = document.getElementById('restartBtn');

    // Configuration & State
    const tileCount    = 24;
    let gridSize;
    const fps          = 10;
    const maxApples    = 3;
    let snake, velocity, nextVel, apples, score, gameOver, paused;
    let comboCounter, lastAppleTime, hue;
    let effects;
    let highScore     = parseInt(localStorage.getItem('snakeHighScore'),10) || 0;
    highEl.textContent = highScore;

    // Timing for Fixed FPS
    let lastTime = 0;
    let delta = 0;
    const interval = 1000 / fps;

    // Initialize Game
    function initGame() {
      snake = [{x:12,y:12}, {x:11,y:12}, {x:10,y:12}];
      velocity = {x:1, y:0};
      nextVel = {x:1, y:0};
      apples = [];
      score = 0;
      comboCounter = 0;
      lastAppleTime = 0;
      hue = 0;
      effects = { score: [], particles: [] };
      gameOver = false;
      paused = false;
      scoreEl.textContent = score;
      restartBtn.style.display = 'none';
      pauseBtn.textContent = 'Pause';
      spawnApples();
    }

    // Resize Canvas
    function resizeCanvas(){
      const size = game.clientWidth;
      canvas.width  = size;
      canvas.height = size;
      gridSize      = size / tileCount;
    }
    resizeCanvas();
    window.addEventListener('resize', resizeCanvas);

    // Helper Functions
    function colorGradient(isSnake){
      if(isSnake){
        const c1 = `hsl(${hue},100%,50%)`,
              c2 = `hsl(${(hue+40)%360},100%,60%)`,
              g  = ctx.createLinearGradient(0, 0, canvas.width, canvas.height);
        g.addColorStop(0, c1);
        g.addColorStop(1, c2);
        return g;
      } else {
        const g = ctx.createRadialGradient(0,0,5, 0,0, gridSize*0.6);
        g.addColorStop(0, `hsl(${hue},100%,70%)`);
        g.addColorStop(1, `hsl(${(hue+60)%360},80%,40%)`);
        return g;
      }
    }
    function roundedRect(x,y,w,h,r){
      ctx.beginPath();
      ctx.moveTo(x+r,y);           ctx.lineTo(x+w-r,y);
      ctx.quadraticCurveTo(x+w,y,  x+w,y+r);
      ctx.lineTo(x+w,y+h-r);
      ctx.quadraticCurveTo(x+w,y+h, x+w-r,y+h);
      ctx.lineTo(x+r,y+h);
      ctx.quadraticCurveTo(x,y+h,   x,y+h-r);
      ctx.lineTo(x,y+r);
      ctx.quadraticCurveTo(x,y,     x+r,y);
      ctx.closePath();
      ctx.fill();
    }
    function isEmpty(x,y){
      return !snake.some(s=>s.x===x&&s.y===y) && !apples.some(a=>a.x===x&&a.y===y);
    }

    // Spawn Apples
    function spawnApples(){
      while(apples.length < maxApples){
        const p = {
          x: Math.floor(Math.random() * tileCount),
          y: Math.floor(Math.random() * tileCount)
        };
        if(isEmpty(p.x, p.y)) apples.push(p);
      }
    }

    // Effects
    function addScoreFx(x,y,amt){
      effects.score.push({
        x: x*gridSize + gridSize/2,
        y: y*gridSize + gridSize/2,
        alpha: 1, text: '+'+amt, size: 24
      });
    }
    function addParticles(x,y){
      for(let i=0;i<12;i++){
        effects.particles.push({
          x: x*gridSize + gridSize/2,
          y: y*gridSize + gridSize/2,
          dx: (Math.random()-0.5)*8,
          dy: (Math.random()-0.5)*8,
          alpha: 1, size: Math.random()*4+2
        });
      }
    }
    function updateEffects(){
      for(let i=effects.score.length-1; i>=0; i--){
        const e = effects.score[i];
        e.y -= 1.5;
        e.alpha -= 0.02;
        e.size += 0.3;
        if(e.alpha <= 0) effects.score.splice(i,1);
      }
      for(let i=effects.particles.length-1; i>=0; i--){
        const p = effects.particles[i];
        p.x += p.dx;
        p.y += p.dy;
        p.alpha -= 0.03;
        p.color = `hsla(${(hue + i*30)%360},100%,60%,${p.alpha})`;
        if(p.alpha <= 0) effects.particles.splice(i,1);
      }
    }
    function flashScore(){
      sb.classList.add('flash');
      setTimeout(()=> sb.classList.remove('flash'), 200);
      try {
        eatSfx.currentTime = 0;
        eatSfx.play();
      } catch(e) {}
    }

    // Update Game Logic
    function update(){
      if((nextVel.x !== -velocity.x || nextVel.y !== -velocity.y)
       &&(nextVel.x !== velocity.x  || nextVel.y !== velocity.y)) {
        velocity = nextVel;
      }

      const head = {
        x: (snake[0].x + velocity.x + tileCount) % tileCount,
        y: (snake[0].y + velocity.y + tileCount) % tileCount
      };

      if(snake.some(p=>p.x===head.x && p.y===head.y)){
        gameOver = true;
        showGameOver();
        return;
      }

      snake.unshift(head);

      let ate = false;
      for(let i=0; i<apples.length; i++){
        if(apples[i].x===head.x && apples[i].y===head.y){
          const now = Date.now();
          const timeBonus  = (now - lastAppleTime < 3000) ? 5 : 0;
          const comboBonus = comboCounter * 2;
          const gain      = 10 + timeBonus + comboBonus;
          score += gain;
          comboCounter++;
          lastAppleTime = now;
          scoreEl.textContent = score;
          if(score > highScore){
            highScore = score;
            localStorage.setItem('snakeHighScore', highScore);
            highEl.textContent = highScore;
          }
          addScoreFx(head.x, head.y, gain);
          addParticles(head.x, head.y);
          flashScore();
          apples.splice(i,1);
          spawnApples();
          ate = true;
          break;
        }
      }
      if(!ate){
        comboCounter = 0;
        snake.pop();
      }
    }

    // Draw Game
    function draw(){
      ctx.clearRect(0, 0, canvas.width, canvas.height);

      // Grid
      ctx.strokeStyle = '#222';
      ctx.lineWidth = 1;
      for(let i=0; i<=tileCount; i++){
        const pos = i * gridSize;
        ctx.beginPath();
        ctx.moveTo(pos, 0);
        ctx.lineTo(pos, canvas.height);
        ctx.moveTo(0, pos);
        ctx.lineTo(canvas.width, pos);
        ctx.stroke();
      }

      // Apples
      apples.forEach(a=>{
        const cx = a.x*gridSize + gridSize/2;
        const cy = a.y*gridSize + gridSize/2;
        ctx.save();
        ctx.translate(cx, cy);
        ctx.shadowColor = '#f44';
        ctx.shadowBlur = 18;
        ctx.fillStyle = colorGradient(false);
        ctx.beginPath();
        ctx.ellipse(0,0, gridSize*0.4, gridSize*0.55, Math.PI/6, 0, 2*Math.PI);
        ctx.fill();
        ctx.fillStyle = '#282';
        ctx.beginPath();
        ctx.ellipse(0, -gridSize*0.3, gridSize*0.15, gridSize*0.3, Math.PI/4, 0, 2*Math.PI);
        ctx.fill();
        ctx.restore();
      });

      // Snake
      snake.forEach((s,i)=>{
        const px = s.x*gridSize, py = s.y*gridSize;
        ctx.save();
        ctx.fillStyle = colorGradient(true);
        ctx.shadowColor = '#0ff';
        ctx.shadowBlur = (i===0 ? 25 : 18);
        roundedRect(px+2, py+2, gridSize-4, gridSize-4, 8);
        ctx.restore();
      });

      // Effects
      effects.particles.forEach(p=>{
        ctx.fillStyle = p.color;
        ctx.beginPath();
        ctx.arc(p.x, p.y, p.size, 0, 2*Math.PI);
        ctx.fill();
      });
      effects.score.forEach(e=>{
        ctx.fillStyle = `rgba(0,255,150,${e.alpha})`;
        ctx.font = `${e.size}px Arial`;
        ctx.textAlign = 'center';
        ctx.shadowColor = '#0f9';
        ctx.shadowBlur = 10;
        ctx.fillText(e.text, e.x, e.y);
      });

      // Paused Overlay
      if (paused) {
        ctx.fillStyle = 'rgba(0,0,0,0.5)';
        ctx.fillRect(0, 0, canvas.width, canvas.height);
        ctx.fillStyle = '#0f9';
        ctx.font = '48px Arial';
        ctx.textAlign = 'center';
        ctx.fillText('Paused', canvas.width / 2, canvas.height / 2);
      }

      // Game Over Overlay
      if (gameOver) {
        ctx.fillStyle = 'rgba(0,0,0,0.7)';
        ctx.fillRect(0, 0, canvas.width, canvas.height);
        ctx.fillStyle = '#f00';
        ctx.font = '48px Arial';
        ctx.textAlign = 'center';
        ctx.fillText('Game Over', canvas.width / 2, canvas.height / 2 - 40);
        ctx.fillStyle = '#0f9';
        ctx.font = '24px Arial';
        ctx.fillText(`Score: ${score}`, canvas.width / 2, canvas.height / 2 + 20);
        ctx.fillText('Press Restart to play again', canvas.width / 2, canvas.height / 2 + 60);
      }
    }

    // Input Handling
    let touchStart = null;
    const minSwipe = 30;

    canvas.addEventListener('touchstart', e=>{
      if(e.touches.length === 1) {
        touchStart = { x: e.touches[0].clientX, y: e.touches[0].clientY };
      }
    }, { passive: true });

    canvas.addEventListener('touchmove', e=>{
      if(!touchStart) return;
      const dx = e.touches[0].clientX - touchStart.x;
      const dy = e.touches[0].clientY - touchStart.y;
      if(Math.abs(dx) > minSwipe || Math.abs(dy) > minSwipe){
        const dir = Math.abs(dx) > Math.abs(dy) ? (dx > 0 ? 'right' : 'left') : (dy > 0 ? 'down' : 'up');
        changeDir(dir);
        touchStart = null;
      }
    }, { passive: true });

    canvas.addEventListener('touchend', () => { touchStart = null; });

    btns.forEach(b => b.addEventListener('click', () => changeDir(b.dataset.dir)));

    window.addEventListener('keydown', e => {
      if (e.key === ' ') {
        e.preventDefault();
        if (!gameOver) {
          paused = !paused;
          pauseBtn.textContent = paused ? 'Resume' : 'Pause';
        }
      } else {
        const keyMap = {
          ArrowUp: 'up',
          ArrowDown: 'down',
          ArrowLeft: 'left',
          ArrowRight: 'right',
          w: 'up',
          s: 'down',
          a: 'left',
          d: 'right'
        };
        const dir = keyMap[e.key];
        if (dir) {
          e.preventDefault();
          changeDir(dir);
        }
      }
    });

    function changeDir(dir){
      const map = { up:{x:0,y:-1}, down:{x:0,y:1}, left:{x:-1,y:0}, right:{x:1,y:0} };
      const nv = map[dir];
      if(nv && (nv.x !== -velocity.x || nv.y !== -velocity.y)) nextVel = nv;
    }

    // Pause and Game Over
    pauseBtn.addEventListener('click', () => {
      if (!gameOver) {
        paused = !paused;
        pauseBtn.textContent = paused ? 'Resume' : 'Pause';
      }
    });

    function showGameOver(){
      gameOver = true;
      restartBtn.style.display = 'block';
      restartBtn.focus();
    }

    restartBtn.addEventListener('click', () => {
      initGame();
    });

    // Main Loop
    function loop(ts=0){
      if(!lastTime) lastTime = ts;
      delta += ts - lastTime;
      lastTime = ts;
      hue = (hue + 2) % 360; // Smooth color shift

      updateEffects();

      while(delta >= interval){
        if (!paused && !gameOver) {
          update();
        }
        delta -= interval;
      }
      draw();
      requestAnimationFrame(loop);
    }

    // Start Game
    initGame();
    requestAnimationFrame(loop);
  })();
  </script>
</body>
</html>