body {
    text-align: center;
    font-family: Arial;
    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;
    font-size: 2.5em;
    background: white;
    border: 2px solid #ccc;
    display: flex;
    justify-content: center;
    align-items: center;
    cursor: pointer;
}

.cell.taken {
    cursor: not-allowed;
    color: #444;
}