body {
    display: flex;
    background-color: gray;
    flex-direction: column;
    align-items: center;
    font-family: Arial, sans-serif;
}

#grid {
    display: grid;
    grid-template-columns: repeat(7,50px);
    grid-template-rows: repeat(7, 50px);
    gap: 5px;
}

.cell {
    width: 50px;
    height: 50px;
    background-color: black;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 24px;
}

.cell.on {
    background-color: white;
}