body {
            font-family: Arial, sans-serif;
            background-color: #f4f4f4;
            margin: 0;
            padding: 0;
        }
        .container {
            width: 80%;
            margin: auto;
            padding: 20px;
            text-align: center;
        }
        .game-board {
            display: grid;
            grid-template-columns: repeat(4, 100px);
            grid-gap: 10px;
            justify-content: center;
        }
        .card {
            width: 100px;
            height: 100px;
            background-color: #fff;
            border: 2px solid #333;
            border-radius: 8px;
            cursor: pointer;
            position: relative;
            overflow: hidden;
            transition: transform 0.3s;
        }
        .card img {
            width: 100%;
            height: 100%;
            position: absolute;
            top: 0;
            left: 0;
            object-fit: cover;
            transition: opacity 0.3s;
        }
        .card.flip img.front {
            opacity: 1;
        }
        .card:not(.flip) img.front {
            opacity: 0;
        }
        .card.flip img.back {
            opacity: 0;
        }
        .card:not(.flip) img.back {
            opacity: 1;
        }