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

#game-board {
    display: grid;
    grid-template-columns: repeat(2, 150px);
    grid-template-rows: repeat(2, 150px);
    gap: 10px;
    justify-content: center;
    margin: 20px auto;
}

.tile {
    width: 150px;
    height: 150px;
    border-radius: 10px;
    opacity: 0.8;
    transition: opacity 0.2s ease-in-out;
    cursor: pointer;
}

    .tile.active {
        opacity: 1;
        box-shadow: 0 0 20px white;
    }

.red {
    background: #f25022;
}

.green {
    background: #7fba00;
}

.blue {
    background: #00a4ef;
}

.yellow {
    background: #ffb900;
}

button {
    padding: 10px 20px;
    font-size: 1rem;
    margin-top: 20px;
}