:root {
    --bg-color: #F9F7F2; /* Claude soft cream */
    --text-color: #1D1D1B; /* Claude deep gray */
    --accent-purple: #6B4E71; /* Claude related mauve */
    --grid-bg: #E8E2D6; /* Muted beige grid */
    --cell-bg: #D4CDBC; /* Empty cell color */
    
    --tile-2-bg: #FFFFFF;
    --tile-2-text: #1D1D1B;
    --tile-4-bg: #FDFBFA;
    --tile-4-text: #1D1D1B;
    --tile-8-bg: #D97757;
    --tile-8-text: #FFFFFF;
    --tile-16-bg: #D98C5F;
    --tile-16-text: #FFFFFF;
    --tile-32-bg: #D16666;
    --tile-32-text: #FFFFFF;
    --tile-64-bg: #C14343;
    --tile-64-text: #FFFFFF;
    --tile-128-bg: #D1A366;
    --tile-128-text: #FFFFFF;
    --tile-256-bg: #B8A35E;
    --tile-256-text: #FFFFFF;
    --tile-512-bg: #A3A35E;
    --tile-512-text: #FFFFFF;
    --tile-1024-bg: #8E8E4E;
    --tile-1024-text: #FFFFFF;
    --tile-2048-bg: #6B4E71; /* Matches accent purple */
    --tile-2048-text: #FFFFFF;
    
    --font-main: 'Outfit', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    --border-radius: 6px;
    --grid-gap: 12px;
    --tile-size: 100px;
}

@media screen and (max-width: 500px) {
    :root {
        --tile-size: 70px;
        --grid-gap: 8px;
    }
}

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

body {
    background-color: var(--bg-color);
    color: var(--text-color);
    font-family: var(--font-main);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    padding: 20px;
}

.container {
    width: 100%;
    max-width: 480px;
}

header {
    margin-bottom: 30px;
}

.title-row {
    display: flex;
    justify-content: space-between;
    align-items: flex-end;
}

.title {
    font-size: 64px;
    font-weight: 700;
    letter-spacing: -2px;
    color: var(--accent-purple);
}

.scores-container {
    display: flex;
    gap: 8px;
}

.score-box {
    background: var(--grid-bg);
    padding: 10px 15px;
    border-radius: var(--border-radius);
    text-align: center;
    min-width: 80px;
}

.score-label {
    font-size: 12px;
    font-weight: 600;
    text-transform: uppercase;
    color: var(--text-color);
    opacity: 0.6;
}

.score-value {
    font-size: 24px;
    font-weight: 700;
}

.subtitle-row {
    margin-top: 10px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.intro {
    font-size: 16px;
    line-height: 1.5;
    color: var(--text-color);
    opacity: 0.8;
}

.restart-button {
    background: var(--text-color);
    color: var(--bg-color);
    border: none;
    padding: 10px 20px;
    border-radius: var(--border-radius);
    font-weight: 600;
    font-size: 16px;
    cursor: pointer;
    transition: transform 0.1s ease, opacity 0.2s ease;
}

.restart-button:hover {
    opacity: 0.9;
}

.restart-button:active {
    transform: scale(0.95);
}

/* Game Area */
.game-area {
    position: relative;
    background: var(--grid-bg);
    border-radius: var(--border-radius);
    padding: var(--grid-gap);
    width: fit-content;
    margin: 0 auto;
    box-shadow: 0 4px 12px rgba(0,0,0,0.05);
}

.grid-container {
    display: grid;
    grid-template-columns: repeat(4, var(--tile-size));
    grid-template-rows: repeat(4, var(--tile-size));
    gap: var(--grid-gap);
}

.grid-cell {
    width: var(--tile-size);
    height: var(--tile-size);
    background: var(--cell-bg);
    border-radius: var(--border-radius);
}

.tile-container {
    position: absolute;
    top: var(--grid-gap);
    left: var(--grid-gap);
    z-index: 10;
}

.tile {
    position: absolute;
    width: var(--tile-size);
    height: var(--tile-size);
    border-radius: var(--border-radius);
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: calc(var(--tile-size) * 0.4);
    font-weight: 700;
    transition: transform 150ms cubic-bezier(0.4, 0, 0.2, 1);
    user-select: none;
}

.tile-inner {
    width: 100%;
    height: 100%;
    border-radius: var(--border-radius);
    display: flex;
    justify-content: center;
    align-items: center;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

/* Position Classes */
.pos-0-0 { transform: translate(0, 0); }
.pos-0-1 { transform: translate(calc(var(--tile-size) + var(--grid-gap)), 0); }
.pos-0-2 { transform: translate(calc(2 * (var(--tile-size) + var(--grid-gap))), 0); }
.pos-0-3 { transform: translate(calc(3 * (var(--tile-size) + var(--grid-gap))), 0); }

.pos-1-0 { transform: translate(0, calc(var(--tile-size) + var(--grid-gap))); }
.pos-1-1 { transform: translate(calc(var(--tile-size) + var(--grid-gap)), calc(var(--tile-size) + var(--grid-gap))); }
.pos-1-2 { transform: translate(calc(2 * (var(--tile-size) + var(--grid-gap))), calc(var(--tile-size) + var(--grid-gap))); }
.pos-1-3 { transform: translate(calc(3 * (var(--tile-size) + var(--grid-gap))), calc(var(--tile-size) + var(--grid-gap))); }

.pos-2-0 { transform: translate(0, calc(2 * (var(--tile-size) + var(--grid-gap)))); }
.pos-2-1 { transform: translate(calc(var(--tile-size) + var(--grid-gap)), calc(2 * (var(--tile-size) + var(--grid-gap)))); }
.pos-2-2 { transform: translate(calc(2 * (var(--tile-size) + var(--grid-gap))), calc(2 * (var(--tile-size) + var(--grid-gap)))); }
.pos-2-3 { transform: translate(calc(3 * (var(--tile-size) + var(--grid-gap))), calc(2 * (var(--tile-size) + var(--grid-gap)))); }

.pos-3-0 { transform: translate(0, calc(3 * (var(--tile-size) + var(--grid-gap)))); }
.pos-3-1 { transform: translate(calc(var(--tile-size) + var(--grid-gap)), calc(3 * (var(--tile-size) + var(--grid-gap)))); }
.pos-3-2 { transform: translate(calc(2 * (var(--tile-size) + var(--grid-gap))), calc(3 * (var(--tile-size) + var(--grid-gap)))); }
.pos-3-3 { transform: translate(calc(3 * (var(--tile-size) + var(--grid-gap))), calc(3 * (var(--tile-size) + var(--grid-gap)))); }

/* Tile Value Colors */
.tile-2 .tile-inner { background: var(--tile-2-bg); color: var(--tile-2-text); }
.tile-4 .tile-inner { background: var(--tile-4-bg); color: var(--tile-4-text); }
.tile-8 .tile-inner { background: var(--tile-8-bg); color: var(--tile-8-text); }
.tile-16 .tile-inner { background: var(--tile-16-bg); color: var(--tile-16-text); }
.tile-32 .tile-inner { background: var(--tile-32-bg); color: var(--tile-32-text); }
.tile-64 .tile-inner { background: var(--tile-64-bg); color: var(--tile-64-text); }
.tile-128 .tile-inner { background: var(--tile-128-bg); color: var(--tile-128-text); font-size: calc(var(--tile-size) * 0.35); }
.tile-256 .tile-inner { background: var(--tile-256-bg); color: var(--tile-256-text); font-size: calc(var(--tile-size) * 0.35); }
.tile-512 .tile-inner { background: var(--tile-512-bg); color: var(--tile-512-text); font-size: calc(var(--tile-size) * 0.35); }
.tile-1024 .tile-inner { background: var(--tile-1024-bg); color: var(--tile-1024-text); font-size: calc(var(--tile-size) * 0.3); }
.tile-2048 .tile-inner { background: var(--tile-2048-bg); color: var(--tile-2048-text); font-size: calc(var(--tile-size) * 0.3); }

/* Animations */
@keyframes pop {
    0% { transform: scale(0); }
    100% { transform: scale(1); }
}

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

.tile-new .tile-inner {
    animation: pop 200ms ease-out;
}

.tile-merged .tile-inner {
    animation: merge 200ms ease-in-out;
}

/* Overlay */
.overlay {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(249, 247, 242, 0.7);
    z-index: 100;
    display: none;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    border-radius: var(--border-radius);
    backdrop-filter: blur(4px);
    text-align: center;
}

.overlay h2 {
    font-size: 48px;
    margin-bottom: 20px;
    color: var(--accent-purple);
}

.overlay button {
    background: var(--accent-purple);
    color: white;
    padding: 12px 30px;
}

footer {
    margin-top: 40px;
    font-size: 14px;
    line-height: 1.6;
    color: var(--text-color);
    opacity: 0.6;
}

/* Fortune Explosion Particles */
.fortune-particle {
    position: absolute;
    z-index: 1000;
    pointer-events: none;
    display: flex;
    justify-content: center;
    align-items: center;
    animation: explode 1s cubic-bezier(0.1, 0.8, 0.3, 1) forwards;
}

@keyframes explode {
    0% {
        transform: translate(-50%, -50%) scale(0) rotate(0deg);
        opacity: 1;
    }
    15% {
        transform: translate(-50%, -50%) scale(1.5) rotate(45deg);
    }
    100% {
        transform: translate(calc(-50% + var(--dx)), calc(-50% + var(--dy))) scale(0) rotate(var(--dr));
        opacity: 0;
    }
}

.merge-flash {
    position: absolute;
    width: var(--tile-size);
    height: var(--tile-size);
    background: white;
    border-radius: 50%;
    transform: translate(-50%, -50%) scale(0);
    z-index: 999;
    pointer-events: none;
    animation: flash-burst 0.4s ease-out forwards;
    box-shadow: 0 0 50px 20px white;
    opacity: 0.8;
}

@keyframes flash-burst {
    0% { transform: translate(-50%, -50%) scale(0); opacity: 0.8; }
    100% { transform: translate(-50%, -50%) scale(2.5); opacity: 0; }
}

/* Red Hare Animation */
.red-hare-container {
    position: fixed;
    top: 50%;
    left: -150px;
    transform: translateY(-50%);
    font-size: 100px;
    z-index: 2000;
    pointer-events: none;
    white-space: nowrap;
    display: flex;
    align-items: center;
    gap: 10px;
}

.horse-icon {
    filter: drop-shadow(0 0 10px #C14343);
}

.milestone-text {
    font-size: 40px;
    font-weight: 800;
    color: #C14343;
    background: rgba(255, 255, 255, 0.9);
    padding: 10px 30px;
    border-radius: 50px;
    box-shadow: 0 4px 15px rgba(0,0,0,0.1);
}

.run-across {
    animation: horse-gallop 2.5s cubic-bezier(0.45, 0.05, 0.55, 0.95) forwards;
}

@keyframes horse-gallop {
    0% { left: -300px; }
    30% { left: 50%; transform: translate(-50%, -50%) scale(1.2); }
    70% { left: 50%; transform: translate(-50%, -50%) scale(1.2); }
    100% { left: calc(100% + 300px); }
}

.highlight {
    color: var(--accent-purple);
    font-weight: 600;
    opacity: 1;
}