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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: #0f0f1a;
    color: #e0e0e0;
    line-height: 1.6;
    min-height: 100vh;
}

main {
    max-width: 800px;
    margin: 0 auto;
    padding: 1rem;
}

.back-link {
    display: inline-block;
    color: #4ecca3;
    text-decoration: none;
    margin-bottom: 0.5rem;
}

.back-link:hover {
    text-decoration: underline;
}

h1 {
    text-align: center;
    color: #f5b942;
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

.game-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.75rem;
    margin-bottom: 2rem;
}

.score-board {
    display: flex;
    gap: 2rem;
    font-size: 1.1rem;
}

.score-board strong {
    color: #f5b942;
}

.grid-wrapper {
    position: relative;
    width: 100%;
    max-width: 340px;
}

.grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 8px;
    background: #1a1a2e;
    padding: 8px;
    border-radius: 8px;
    border: 2px solid #f5b942;
}

.tile {
    aspect-ratio: 1;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.5rem;
    font-weight: bold;
    border-radius: 4px;
    background: #2a2a3e;
    color: #e0e0e0;
    transition: transform 0.1s ease;
}

.tile[data-value="2"] {
    background: #eee4da;
    color: #776e65;
}

.tile[data-value="4"] {
    background: #ede0c8;
    color: #776e65;
}

.tile[data-value="8"] {
    background: #f2b179;
    color: #f9f6f2;
}

.tile[data-value="16"] {
    background: #f59563;
    color: #f9f6f2;
}

.tile[data-value="32"] {
    background: #f67c5f;
    color: #f9f6f2;
}

.tile[data-value="64"] {
    background: #f65e3b;
    color: #f9f6f2;
}

.tile[data-value="128"] {
    background: #edcf72;
    color: #f9f6f2;
    font-size: 1.3rem;
}

.tile[data-value="256"] {
    background: #edcc61;
    color: #f9f6f2;
    font-size: 1.3rem;
}

.tile[data-value="512"] {
    background: #edc850;
    color: #f9f6f2;
    font-size: 1.3rem;
}

.tile[data-value="1024"] {
    background: #edc53f;
    color: #f9f6f2;
    font-size: 1.1rem;
}

.tile[data-value="2048"] {
    background: #edc22e;
    color: #f9f6f2;
    font-size: 1.1rem;
    box-shadow: 0 0 20px #edc22e;
}

.tile[data-value="4096"],
.tile[data-value="8192"],
.tile[data-value="16384"],
.tile[data-value="32768"] {
    background: #3c3a32;
    color: #f9f6f2;
    font-size: 0.9rem;
}

.tile.new {
    animation: appear 0.15s ease;
}

.tile.merged {
    animation: pop 0.15s ease;
}

@keyframes appear {
    0% {
        transform: scale(0);
    }
    100% {
        transform: scale(1);
    }
}

@keyframes pop {
    0% {
        transform: scale(1);
    }
    50% {
        transform: scale(1.15);
    }
    100% {
        transform: scale(1);
    }
}

.overlay {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(15, 15, 26, 0.92);
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    gap: 1rem;
    border-radius: 8px;
    z-index: 10;
}

.overlay.hidden {
    display: none;
}

.overlay p {
    font-size: 1.5rem;
    color: #f5b942;
}

.overlay p:first-child {
    font-size: 2rem;
}

.overlay button {
    padding: 0.75rem 2rem;
    font-size: 1rem;
    background: #f5b942;
    color: #0f0f1a;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-weight: 600;
    margin: 0.25rem;
}

.overlay button:hover {
    background: #e5a932;
}

.overlay .share-btn {
    background: #4ecca3;
    margin-top: 0.5rem;
}

.overlay .share-btn:hover {
    background: #3dbb92;
}

.controls {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
    margin-top: 0.5rem;
}

.control-row {
    display: flex;
    gap: 0.5rem;
}

.control-btn {
    width: 3.5rem;
    height: 3.5rem;
    font-size: 1.25rem;
    background: #1a1a2e;
    color: #f5b942;
    border: 2px solid #f5b942;
    border-radius: 8px;
    cursor: pointer;
    user-select: none;
    -webkit-tap-highlight-color: transparent;
}

.control-btn:active {
    background: #f5b942;
    color: #0f0f1a;
}

.instructions {
    font-size: 0.9rem;
    color: #888;
    text-align: center;
}

.content {
    padding-top: 1rem;
    border-top: 1px solid #2a2a3e;
}

.content h2 {
    color: #f5b942;
    font-size: 1.25rem;
    margin: 1.5rem 0 0.75rem;
}

.content h2:first-child {
    margin-top: 1rem;
}

.content p {
    margin-bottom: 0.75rem;
}

.content ul {
    margin: 0.5rem 0 1rem 1.5rem;
}

.content li {
    margin-bottom: 0.5rem;
}

.content a {
    color: #f5b942;
}

.content a:hover {
    text-decoration: none;
}

@media (min-width: 600px) {
    main {
        padding: 2rem;
    }

    h1 {
        font-size: 3rem;
    }

    .grid {
        gap: 12px;
        padding: 12px;
    }

    .tile {
        font-size: 2rem;
    }

    .tile[data-value="128"],
    .tile[data-value="256"],
    .tile[data-value="512"] {
        font-size: 1.75rem;
    }

    .tile[data-value="1024"],
    .tile[data-value="2048"] {
        font-size: 1.5rem;
    }

    .tile[data-value="4096"],
    .tile[data-value="8192"],
    .tile[data-value="16384"],
    .tile[data-value="32768"] {
        font-size: 1.25rem;
    }

    .controls {
        display: none;
    }

    .instructions {
        font-size: 1rem;
    }
}

@media (hover: none) {
    .controls {
        display: flex;
    }
}