body {
    font-family: Arial, sans-serif;
    display: flex;
    flex-direction: column;
    align-items: center;
    background-color: #f0f0f0;
}

h1 {
    margin-bottom: 1rem;
}

#game-board {
    display: flex;
    flex-direction: column;
    width: 300px;
    height: 300px;
    background-color: white;
    border: 1px solid black;
}

.row {
    display: flex;
    flex-direction: row;
    height: 33.33%;
}

.cell {
    display: flex;
    justify-content: center;
    align-items: center;
    width: 33.33%;
    height: 100%;
    border: 1px solid black;
    cursor: pointer;
}

.cell[data-mark="1"]::before {
    content: "X";
    font-size: 2rem;
    color: #2196F3;
}

.cell[data-mark="2"]::before {
    content: "O";
    font-size: 2rem;
    color: #F44336;
}