body {
      font-family: 'Arial', sans-serif;
      text-align: center;
      background-color: #f9f9f9;
      color: #333;
      margin: 0;
      padding: 0;
    }

    .container {
      max-width: 100%;
      margin: 50px auto;
      padding: 20px;
      background: #fff;
      border-radius: 12px;
      box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
    }

    h1 {
      color: #4CAF50;
      font-size: 24px;
      margin-bottom: 20px;
    }

    .card {
      margin: 20px 0;
      padding: 20px;
      background: #f7f7f7;
      border-radius: 12px;
      box-shadow: 0 3px 10px rgba(0, 0, 0, 0.1);
    }

    .letter {
      font-size: 64px;
      font-weight: bold;
      color: #333;
    }

    .input-section {
      margin: 20px 0;
    }

    input {
      font-size: 16px;
      padding: 8px;
      width: 95%;
      max-width: 300px;
      border: 2px solid #ccc;
      border-radius: 6px;
      outline: none;
      box-sizing: border-box;
    }

    input:focus {
      border-color: #4CAF50;
    }

    .feedback {
      margin-top: 10px;
      font-size: 16px;
      font-weight: bold;
    }

    .btn {
      margin-top: 20px;
      padding: 12px 24px;
      font-size: 16px;
      font-weight: bold;
      background-color: #4CAF50;
      color: white;
      border: none;
      border-radius: 6px;
      cursor: pointer;
      transition: background-color 0.3s ease;
      display: inline-flex;
      align-items: center;
      gap: 8px;
    }

    .btn:hover {
      background-color: #45a049;
    }

    .btn i {
      font-size: 18px;
    }

    .canvas-container {
      margin-top: 30px;
    }

    canvas {
      border: 2px solid #ccc;
      border-radius: 6px;
      width: 100%;
      max-width: 300px;
    }

    @media (max-width: 768px) {
      .container {
        margin: 20px;
        padding: 15px;
      }

      .letter {
        font-size: 48px;
      }

      .btn {
        padding: 10px 20px;
        font-size: 14px;
      }

      .input-section {
        margin: 15px 0;
      }

      .feedback {
        font-size: 14px;
      }

      canvas {
        max-width: 100%;
        height: auto;
      }
    }