body {
      margin: 0;
      padding: 0;
      font-family: Arial, sans-serif;
      text-align: center;
      background-color: #f0f8ff;
    }


    h1 {
      margin-top: 20px;
      margin-bottom: 10px;
    }


    .btn {
      padding: 10px 20px;
      margin: 15px;
      font-size: 16px;
      cursor: pointer;
      border-radius: 5px;
      background-color: #6c90c6;
      color: white;
      border: none;
    }


    .grid table {
      margin: 0 auto;
      border-collapse: collapse;
    }


    td {
      width: 80px;
      height: 80px;
      font-size: 40px;
      text-align: center;
      vertical-align: middle;
      border: 2px solid #333;
      cursor: pointer;
      user-select: none;
    }


    td:hover {
      background-color: #d1e7dd;
    }