body {
    font-family: Arial, sans-serif;
    text-align: center;
    background-color: #f0f0f0;
}

#grid {
    display: grid;
    grid-template-columns: repeat(16, 1fr);
    grid-template-rows: repeat(4, 1fr);
    gap: 5px;
    width: 80%;
    max-width: 800px;
    margin: 20px auto;
}

.pad {
    width: 100%;
    height: 50px;
    background-color: #ddd;
    border: 1px solid #ccc;
    cursor: pointer;
    transition: background-color 0.2s;
}

.pad.active {
    background-color: #4CAF50;
}

button {
    margin: 10px;
    padding: 10px 20px;
    font-size: 16px;
    cursor: pointer;
}