Flip Memory

<div class="flip-memory">
    <div class="memory-card">?</div>
    <div class="memory-card">?</div>
</div>

.flip-memory {
    display: flex;
    gap: 15px;
}

.memory-card {
    width: 80px;
    height: 80px;
    background: linear-gradient(135deg, #667eea, #764ba2);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2rem;
    font-weight: 900;
    color: white;
    border-radius: 12px;
    cursor: pointer;
    transition: transform 0.6s;
    transform-style: preserve-3d;
    animation: memoryFlip 3s ease-in-out infinite;
}

.memory-card:nth-child(2) {
    animation-delay: 1.5s;
}

@keyframes memoryFlip {
    0%, 40%, 100% {
        transform: rotateY(0deg);
    }
    20% {
        transform: rotateY(180deg);
    }
}