body {
    font-family: Arial, sans-serif;
    text-align: center;
    background: #f2f2f2;
}

h1 {
    margin-top: 20px;
}

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

.cell {
    width: 100px;
    height: 100px;
    background: #000;
    cursor: pointer;
}

.green {
    background: green;
}

.red {
    background: red;
}

#message {
    margin-top: 20px;
    font-size: 18px;
}

button {
    margin-top: 15px;
    padding: 8px 15px;
    font-size: 16px;
    cursor: pointer;
}