body {
            font-family: Arial, sans-serif;
            text-align: center;
            padding: 20px;
        }
        .button-container {
            display: flex;
            flex-wrap: wrap;
            justify-content: center;
            gap: 10px;
        }
        .note-button {
            padding: 15px;
            font-size: 18px;
            width: 80px;
            height: 50px;
            border: 1px solid #ccc;
            background-color: #f8f8f8;
            cursor: pointer;
            border-radius: 5px;
        }
        .note-button.active {
            background-color: #4CAF50;
            color: white;
        }
        button.submit {
            margin-top: 20px;
            padding: 15px 30px;
            font-size: 20px;
            background-color: #008CBA;
            color: white;
            border: none;
            border-radius: 5px;
            cursor: pointer;
        }
button.sound {
            margin-top: 12px;
            padding: 5px 7px;
            font-size: 8px;
            background-color: #4682b4;
            color: white;
            border: none;
            border-radius: 5px;
            cursor: pointer;
        }
letter {
    text-align: center;
        }