:root {
    --bg-color: #f0f2f5;
    --card-back: #2c3e50;
    --card-front: #ffffff;
    --primary: #3498db;
    --success: #2ecc71;
    --text: #2c3e50;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
    background-color: var(--bg-color);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    color: var(--text);
}

#game-container {
    width: 100%;
    max-width: 800px;
    padding: 20px;
    text-align: center;
}

header {
    margin-bottom: 20px;
}

h1 {
    margin-bottom: 10px;
    font-size: 1.8rem;
}

.stats {
    display: flex;
    justify-content: center;
    gap: 30px;
    font-size: 1.1rem;
}

.board {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 12px;
    perspective: 1000px;
    margin: 0 auto;
}

@media (max-width: 500px) {
    .board {
        grid-template-columns: repeat(3, 1fr);
    }
    /* If 16 cards, 3 columns leaves one row incomplete, 
       but we'll handle 4x4 or 4x2 logic in JS */
}

.card {
    aspect-ratio: 3/4;
    position: relative;
    cursor: pointer;
    transform-style: preserve-3d;
    transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
}

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

.card.matched {
    cursor: default;
}

.card-face {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 10px;
    border-radius: 8px;
    box-shadow: 0 4px 8px rgba(0,0,0,0.1);
    font-size: 0.85rem;
    font-weight: 600;
    overflow: hidden;
}

.card-front {
    background-color: var(--card-back);
    color: white;
}

.card-front::after {
    content: "?";
    font-size: 2rem;
    opacity: 0.3;
}

.card-back {
    background-color: var(--card-front);
    transform: rotateY(180deg);
    border: 3px solid var(--primary);
}

.card.matched .card-back {
    border-color: var(--success);
    background-color: #e8f8f0;
}

/* Modal Styles */
#win-screen, #start-screen {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0,0,0,0.8);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 100;
}

.hidden {
    display: none !important;
}

.modal {
    background: white;
    padding: 40px;
    border-radius: 15px;
    max-width: 90%;
    width: 400px;
}

.modal h2 {
    margin-bottom: 15px;
    color: var(--primary);
}

.modal p {
    margin-bottom: 20px;
}

button {
    background: var(--primary);
    color: white;
    border: none;
    padding: 12px 25px;
    border-radius: 5px;
    font-size: 1rem;
    cursor: pointer;
    transition: background 0.3s;
}

button:hover {
    background: #2980b9;
}