body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-color: #000;
    margin: 0;
}

#board {
    width: 100%;
    max-width: 608px; /* 19 columns × 32px */
    height: auto;
    background-color: black;
    border: 4px solid #b3e5fc;
    border-radius: 8px;
    box-sizing: border-box;
}