* {
    box-sizing: border-box;
    margin: 0;
    padding: 0
}

body {
    font-family: Inter, system-ui, Segoe UI, Arial;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 20px
}

.container {
    background: #fff;
    border-radius: 14px;
    padding: 24px;
    width: 100%;
    max-width: 900px;
    box-shadow: 0 20px 60px rgba(0, 0, 0, .25)
}

h1 {
    color: #333;
    text-align: center;
    margin-bottom: 16px
}

.controls {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 18px
}

.scoreboard {
    display: flex;
    gap: 16px;
    align-items: center
}

.scoreboard div {
    background: linear-gradient(135deg, #667eea, #764ba2);
    color: #fff;
    padding: 8px 12px;
    border-radius: 8px;
    font-weight: 600
}

.buttons button {
    margin-left: 8px;
    padding: 8px 14px;
    border-radius: 8px;
    border: none;
    background: #4ECDC4;
    color: #fff;
    cursor: pointer
}

.board {
    display: grid;
    grid-template-columns: repeat(6, 1fr);
    gap: 12px;
    padding: 12px
}

.card {
    position: relative;
    padding-top: 100%;
    cursor: pointer;
    perspective: 800px
}

.card .inner {
    position: absolute;
    inset: 0;
    transition: transform .5s;
    transform-style: preserve-3d
}

.card.flipped .inner {
    transform: rotateY(180deg)
}

.card .front,
.card .back {
    position: absolute;
    inset: 0;
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    backface-visibility: hidden;
    font-size: 1.2rem
}

.card .front {
    background: #f4f4f4;
    border: 2px solid #ddd
}

.card .back {
    background: #667eea;
    color: #fff;
    transform: rotateY(180deg)
}

.card.matched .inner {
    box-shadow: 0 8px 20px rgba(78, 205, 196, .25);
    outline: 4px solid rgba(78, 205, 196, .12)
}

.card.mismatch {
    animation: shake .4s
}

.overlay {
    position: fixed;
    left: 50%;
    top: 50%;
    transform: translate(-50%, -50%);
    padding: 20px 28px;
    border-radius: 10px;
    background: rgba(0, 0, 0, .65);
    color: #fff;
    font-size: 36px;
    display: none
}

.overlay.visible {
    display: block
}

@keyframes shake {
    0% {
        transform: translateX(0)
    }

    25% {
        transform: translateX(-6px)
    }

    50% {
        transform: translateX(6px)
    }

    75% {
        transform: translateX(-4px)
    }

    100% {
        transform: translateX(0)
    }
}

@media(max-width:800px) {
    .board {
        grid-template-columns: repeat(4, 1fr)
    }
}

@media(max-width:480px) {
    .board {
        grid-template-columns: repeat(3, 1fr)
    }
}