:root {
    --bg-color: #f8fafc;
    --text-primary: #0f172a;
    --accent-color: #3b82f6;
    --accent-alt: #f472b6;
    --grid-bg: #e2e8f0;
    --cell-bg: #cbd5e1;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Outfit', sans-serif;
}

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

.game-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1.5rem;
    width: 100%;
    max-width: 500px;
}

.game-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    width: 100%;
    margin-bottom: 1rem;
}

.back-btn {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    padding: 0.5rem 1.2rem;
    border: 1px solid rgba(0, 0, 0, 0.1);
    border-radius: 20px;
    transition: all 0.3s ease;
    background: transparent;
}

.back-btn:hover {
    background: rgba(0, 0, 0, 0.05);
}

h1 {
    font-size: 2.2rem;
    font-weight: 800;
}

h1 span {
    color: var(--accent-color);
}

.score-container {
    background: #ffffff;
    padding: 0.5rem 1.5rem;
    border-radius: 10px;
    border: 1px solid rgba(0, 0, 0, 0.1);
    display: flex;
    gap: 1.5rem;
}

.score-box {
    display: flex;
    flex-direction: column;
    align-items: center;
    font-size: 0.8rem;
    color: #64748b;
    font-weight: 800;
}

#score, #best-score {
    font-size: 1.5rem;
    color: var(--text-primary);
}

.game-board-container {
    position: relative;
    background: var(--grid-bg);
    padding: 15px;
    border-radius: 15px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.05);
}

#game-board {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-gap: 15px;
    width: 400px;
    height: 400px;
}

.cell {
    background: var(--cell-bg);
    border-radius: 10px;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 2rem;
    font-weight: 800;
    color: #334155;
    transition: all 0.15s ease-in-out;
}

.controls-info {
    color: #64748b;
    font-size: 0.95rem;
    text-align: center;
    margin-top: 1rem;
}

.game-over {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(255, 255, 255, 0.85);
    backdrop-filter: blur(8px);
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    border-radius: 15px;
    z-index: 10;
}

.game-over h2 {
    font-size: 3rem;
    color: var(--text-primary);
    margin-bottom: 1.5rem;
}

.game-over button {
    padding: 1rem 2rem;
    background: var(--accent-color);
    color: #fff;
    border: none;
    font-weight: 800;
    border-radius: 30px;
    cursor: pointer;
    font-size: 1.1rem;
    transition: all 0.3s ease;
    box-shadow: 0 4px 15px rgba(59, 130, 246, 0.2);
}

.game-over button:hover {
    transform: scale(1.05);
    background: #2563eb;
}

/* Tile Colors based on value (Light/Soft palette) */
.cell[data-value="2"] { background: #f1f5f9; color: #334155; }
.cell[data-value="4"] { background: #e2e8f0; color: #334155; }
.cell[data-value="8"] { background: #fed7aa; color: #c2410c; }
.cell[data-value="16"] { background: #fdba74; color: #c2410c; }
.cell[data-value="32"] { background: #fb923c; color: #fff; }
.cell[data-value="64"] { background: #f97316; color: #fff; }
.cell[data-value="128"] { background: #fca5a5; color: #991b1b; font-size: 1.8rem; }
.cell[data-value="256"] { background: #f87171; color: #fff; font-size: 1.8rem; }
.cell[data-value="512"] { background: #ef4444; color: #fff; font-size: 1.8rem; }
.cell[data-value="1024"] { background: #fcd34d; color: #b45309; font-size: 1.5rem; }
.cell[data-value="2048"] { background: #fbbf24; color: #fff; font-size: 1.5rem; }