:root {
    --bg-color: #0d0d0d;
    --text-color: #f2f2f2;
    --red-main: #d30000;
    --red-dark: #8a0000;
    --grid-bg: #1a1a1a;
    --cell-empty: #262626;
    --transition-speed: 150ms;
}

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

body {
    background-color: var(--bg-color);
    color: var(--text-color);
    font-family: 'Roboto', sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    overflow-x: hidden;
}

.container {
    width: 400px;
    max-width: 90vw;
    margin: 20px auto;
}

/* Header & Typography */
header {
    text-align: center;
    margin-bottom: 20px;
}

.btn-retour {
    display: inline-block;
    color: var(--text-color);
    text-decoration: none;
    font-family: 'Oswald', sans-serif;
    text-transform: uppercase;
    font-size: 0.9rem;
    margin-bottom: 20px;
    padding: 5px 10px;
    border: 1px solid var(--red-dark);
    border-radius: 4px;
    transition: all 0.3s ease;
}

.btn-retour:hover {
    background: var(--red-main);
    border-color: var(--red-main);
}

.logo {
    font-family: 'Oswald', sans-serif;
    font-size: 4rem;
    color: var(--text-color);
    margin-bottom: 15px;
    letter-spacing: 4px;
}
.logo span {
    color: var(--red-main);
}

.scores-container {
    display: flex;
    justify-content: center;
    gap: 15px;
    margin-bottom: 20px;
}

.score-box {
    background: var(--grid-bg);
    padding: 10px 20px;
    border-radius: 6px;
    border-left: 3px solid var(--red-main);
}

.score-title {
    display: block;
    font-size: 0.65rem;
    color: #999;
    text-transform: uppercase;
    margin-bottom: 5px;
    font-family: 'Oswald', sans-serif;
}

#score, #best-score {
    font-size: 1.5rem;
    font-weight: bold;
    font-family: 'Oswald', sans-serif;
}

.mission-text {
    font-size: 0.85rem;
    color: #bbb;
    margin-bottom: 20px;
    line-height: 1.4;
}

.btn-action {
    background: var(--red-dark);
    color: #fff;
    border: none;
    padding: 12px 20px;
    font-family: 'Oswald', sans-serif;
    font-size: 1rem;
    cursor: pointer;
    border-radius: 4px;
    text-transform: uppercase;
    transition: background 0.3s;
}

.btn-action:hover {
    background: var(--red-main);
}

/* Game Board */
#game-board {
    position: relative;
    background: var(--grid-bg);
    padding: 10px;
    border-radius: 8px;
    width: 100%;
    aspect-ratio: 1 / 1;
    touch-action: none; /* Prevent scrolling when swiping */
    border: 2px solid var(--red-dark);
    box-shadow: 0 0 20px rgba(211, 0, 0, 0.2);
}

.grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-template-rows: repeat(4, 1fr);
    gap: 10px;
    width: 100%;
    height: 100%;
}

.cell {
    background: var(--cell-empty);
    border-radius: 6px;
    width: 100%;
    height: 100%;
}

#tile-container {
    position: absolute;
    top: 10px;
    left: 10px;
    right: 10px;
    bottom: 10px;
    z-index: 10;
}

.tile {
    position: absolute;
    display: flex;
    justify-content: center;
    align-items: center;
    font-family: 'Oswald', sans-serif;
    font-weight: bold;
    border-radius: 6px;
    transition: transform var(--transition-speed) ease-in-out;
}

.tile-inner {
    width: 100%;
    height: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    border-radius: 6px;
    line-height: 1;
}

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

.tile-merged .tile-inner {
    animation: pop 0.2s;
}

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

/* Overlay Game Over / Win */
#game-over, #game-won {
    position: absolute;
    top: 0; left: 0; right: 0; bottom: 0;
    background: rgba(0,0,0,0.85);
    z-index: 20;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    border-radius: 8px;
    text-align: center;
}

#game-over h2, #game-won h2 {
    font-family: 'Oswald', sans-serif;
    font-size: 2.5rem;
    color: var(--red-main);
    margin-bottom: 10px;
}

#game-over p, #game-won p {
    font-size: 1.2rem;
    margin-bottom: 25px;
}

.hidden {
    display: none !important;
}

/* Tile Colors - Dark & Red Theme */
.tile-2 .tile-inner { background: #333; color: #fff; font-size: 2.5rem; }
.tile-4 .tile-inner { background: #444; color: #fff; font-size: 2.5rem; }
.tile-8 .tile-inner { background: #5a1a1a; color: #fff; font-size: 2.5rem; }
.tile-16 .tile-inner { background: #731b1b; color: #fff; font-size: 2.2rem; }
.tile-32 .tile-inner { background: #8c1e1e; color: #fff; font-size: 2.2rem; }
.tile-64 .tile-inner { background: #a62020; color: #fff; font-size: 2.2rem; }
.tile-128 .tile-inner { background: #bf2323; color: #fff; font-size: 1.8rem; box-shadow: 0 0 10px rgba(255,0,0,0.3); }
.tile-256 .tile-inner { background: #d92525; color: #fff; font-size: 1.8rem; box-shadow: 0 0 15px rgba(255,0,0,0.4); }
.tile-512 .tile-inner { background: #f22626; color: #fff; font-size: 1.8rem; box-shadow: 0 0 20px rgba(255,0,0,0.5); }
.tile-1024 .tile-inner { background: #ff3333; color: #fff; font-size: 1.5rem; box-shadow: 0 0 25px rgba(255,0,0,0.6); }
.tile-2048 .tile-inner { background: #fff; color: var(--red-main); font-size: 1.5rem; box-shadow: 0 0 30px rgba(255,255,255,0.7); }
.tile-super .tile-inner { background: #ffaa00; color: #000; font-size: 1.3rem; }