body {
    font-family: Arial, sans-serif;
    text-align: center;
    background-color: #f4f4f4;
}

h1 {
    margin-top: 20px;
}

.game-board {
    display: grid;
    grid-template-columns: repeat(4, 100px);
    grid-gap: 10px;
    justify-content: center;
    margin: 20px auto;
}

.card {
    width: 100px;
    height: 100px;
    background-color: #2c3e50;
    color: white;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    font-size: 16px;
    cursor: pointer;
    border-radius: 5px;
    user-select: none;
    transition: background-color 0.3s;
}

.card.flipped, .card.matched {
    background-color: #1abc9c;
}