body {
    font-family: Arial, sans-serif;
    text-align: center;
    background: #f4f6fa;
  }
  h1 { margin-top: 30px; }

  #keyboard {
    display: inline-block;
    margin-top: 30px;
  }

  .row {
    display: flex;
    justify-content: center;
    margin-bottom: 5px;
  }

  .key {
    width: 45px;
    height: 45px;
    border: 1px solid #ccc;
    border-radius: 6px;
    line-height: 45px;
    margin: 3px;
    background: white;
    font-weight: bold;
    font-size: 18px;
    transition: background 0.2s, transform 0.1s;
  }

  .key.correct { background: #4caf50; color: white; }
  .key.wrong { background: #f44336; color: white; }

  #question {
    font-size: 60px;
    margin-top: 40px;
    height: 80px;
  }

  #result {
    margin-top: 30px;
    font-size: 24px;
  }

  button {
    margin-top: 20px;
    padding: 10px 24px;
    font-size: 16px;
    background: #2196f3;
    color: white;
    border: none;
    border-radius: 6px;
    cursor: pointer;
  }
  button:hover { background: #1976d2; }

  .toggle {
    margin-left: 10px;
    background: #9e9e9e;
  }
  .toggle.on { background: #4caf50; }