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

#board {
    display: grid;
    grid-template-columns: repeat(3, 100px);
    grid-gap: 5px;
    justify-content: center;
    margin: 20px auto;
}

.cell {
    width: 100px;
    height: 100px;
    background-color: #fff;
    font-size: 2em;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    border: 1px solid #ccc;
}

.cell.taken {
    cursor: default;
    color: #444;
}