body {
      margin: 0;
      background: black;
      color: white;
      font-family: Arial, sans-serif;
      overflow: hidden;
      text-align: center;
    }
    #gameCanvas {
      background: #111;
      display: block;
      margin: 20px auto;
      border: 3px solid white;
    }
    #restartBtn {
      display: none;
      margin-top: 10px;
      padding: 10px 20px;
      font-size: 18px;
      background: #fff;
      color: #000;
      border: none;
      border-radius: 5px;
      cursor: pointer;
    }
    #restartBtn:hover {
      background: #ccc;
    }