:root {
    --primary-color: #4a6fa5;
    --secondary-color: #166088;
    --accent-color: #4fc3f7;
    --background-color: #f8f9fa;
    --text-color: #333;
    --card-color: #fff;
    --shadow-color: rgba(0, 0, 0, 0.1);
    --success-color: #4caf50;
}

[data-theme="dark"] {
    --primary-color: #3a5683;
    --secondary-color: #0d4b6e;
    --accent-color: #0288d1;
    --background-color: #121212;
    --text-color: #f5f5f5;
    --card-color: #1e1e1e;
    --shadow-color: rgba(0, 0, 0, 0.3);
    --success-color: #388e3c;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    transition: background-color 0.3s, color 0.3s;
}

body {
    font-family: 'Poppins', sans-serif;
    background-color: var(--background-color);
    color: var(--text-color);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.header {
    background-color: var(--primary-color);
    color: white;
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: 0 2px 10px var(--shadow-color);
}

.header h1 {
    font-size: 1.8rem;
    font-weight: 700;
}

.btn {
    padding: 0.5rem 1rem;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-weight: 600;
    margin-left: 0.5rem;
    background-color: var(--background-color);
    color: var(--text-color);
}

.btn:hover {
    opacity: 0.9;
    transform: translateY(-1px);
}

.btn:active {
    transform: translateY(0);
}

.primary {
    background-color: var(--accent-color);
    color: white;
}

.game-container {
    flex: 1;
    padding: 2rem;
    max-width: 1200px;
    margin: 0 auto;
    width: 100%;
}

.game-info {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
}

.stats {
    display: flex;
    gap: 1.5rem;
    font-weight: 600;
}

.difficulty select {
    padding: 0.5rem;
    border-radius: 4px;
    border: 1px solid var(--shadow-color);
    background-color: var(--card-color);
    color: var(--text-color);
}

.game-board {
    display: grid;
    grid-gap: 1rem;
    margin: 0 auto;
}

.game-board.easy {
    grid-template-columns: repeat(4, 1fr);
    max-width: 600px;
}

.game-board.medium {
    grid-template-columns: repeat(6, 1fr);
    max-width: 800px;
}

.game-board.hard {
    grid-template-columns: repeat(8, 1fr);
    max-width: 1000px;
}

.card {
    aspect-ratio: 1;
    background-color: var(--secondary-color);
    border-radius: 8px;
    display: flex;
    justify-content: center;
    align-items: center;
    cursor: pointer;
    font-size: 0;
    transition: transform 0.3s, background-color 0.3s;
    box-shadow: 0 4px 8px var(--shadow-color);
    position: relative;
    transform-style: preserve-3d;
}

.card:hover {
    transform: scale(1.03);
}

.card.flipped {
    background-color: var(--card-color);
    transform: rotateY(180deg);
    font-size: 2rem;
    color: var(--text-color);
}

.card.matched {
    background-color: var(--success-color);
    cursor: default;
    transform: rotateY(180deg) scale(0.95);
}

.card img {
    width: 80%;
    height: 80%;
    object-fit: contain;
    display: none;
}

.card.flipped img {
    display: block;
}

.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    display: none;
    justify-content: center;
    align-items: center;
    z-index: 100;
}

.modal-content {
    background-color: var(--background-color);
    padding: 2rem;
    border-radius: 8px;
    max-width: 500px;
    width: 90%;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.15);
}

.modal h2 {
    margin-bottom: 1rem;
    color: var(--primary-color);
}

.modal ol {
    padding-left: 1.5rem;
    margin-bottom: 1.5rem;
}

.modal ol li {
    margin-bottom: 0.5rem;
}

.footer {
    text-align: center;
    padding: 1rem;
    background-color: var(--primary-color);
    color: white;
    font-size: 0.9rem;
}

@media (max-width: 768px) {
    .header {
        flex-direction: column;
        gap: 1rem;
        padding: 1rem;
    }

    .game-board.medium {
        grid-template-columns: repeat(4, 1fr);
    }

    .game-board.hard {
        grid-template-columns: repeat(4, 1fr);
    }

    .card {
        font-size: 1.5rem;
    }
}