:root {
  --bg: #121212;
  --board-bg: #1e1e1e;
  --tile-empty: #2a2a2a;
  --tile-2: #eee4da;
  --tile-4: #ede0c8;
  --tile-8: #f2b179;
  --tile-16: #f59563;
  --tile-32: #f67c5f;
  --tile-64: #f65e3b;
  --tile-128: #edcf72;
  --tile-256: #edcc61;
  --tile-512: #edc850;
  --tile-1024: #edc53f;
  --tile-2048: #edc22e;
  --text-dark: #776e65;
  --text-light: #f9f6f2;
  --accent: #ffcc33;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

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

.container {
  text-align: center;
  max-width: 420px;
  padding: 16px;
}

h1 {
  font-size: 2.4rem;
  margin-bottom: 4px;
}

.subtitle {
  font-size: 0.9rem;
  color: #aaa;
  margin-bottom: 16px;
}

.top-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 12px;
}

.score-box {
  background: #1b1b1b;
  padding: 8px 12px;
  border-radius: 6px;
  min-width: 90px;
}

.score-label {
  font-size: 0.75rem;
  text-transform: uppercase;
  color: #ccc;
}

.score-value {
  font-size: 1.2rem;
  font-weight: 700;
  margin-top: 2px;
}

.btn {
  background: var(--accent);
  color: #000;
  border: none;
  border-radius: 6px;
  padding: 8px 14px;
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  transition: transform 0.1s ease, box-shadow 0.1s ease;
}

.btn:hover {
  transform: translateY(-1px);
  box-shadow: 0 4px 10px rgba(0,0,0,0.4);
}

.board {
  background: var(--board-bg);
  border-radius: 8px;
  padding: 10px;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
  margin-top: 8px;
}

.tile {
  width: 80px;
  height: 80px;
  border-radius: 6px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 1.4rem;
  transition: transform 0.08s ease, background 0.08s ease;
}

.tile.empty {
  background: var(--tile-empty);
}

.tile-2 { background: var(--tile-2); color: var(--text-dark); }
.tile-4 { background: var(--tile-4); color: var(--text-dark); }
.tile-8 { background: var(--tile-8); color: var(--text-light); }
.tile-16 { background: var(--tile-16); color: var(--text-light); }
.tile-32 { background: var(--tile-32); color: var(--text-light); }
.tile-64 { background: var(--tile-64); color: var(--text-light); }
.tile-128 { background: var(--tile-128); color: var(--text-light); font-size: 1.2rem; }
.tile-256 { background: var(--tile-256); color: var(--text-light); font-size: 1.2rem; }
.tile-512 { background: var(--tile-512); color: var(--text-light); font-size: 1.2rem; }
.tile-1024 { background: var(--tile-1024); color: var(--text-light); font-size: 1.1rem; }
.tile-2048 { background: var(--tile-2048); color: var(--text-light); font-size: 1.1rem; }

.message {
  margin-top: 10px;
  font-size: 0.9rem;
  color: #ddd;
  min-height: 18px;
}

@media (max-width: 480px) {
  .board {
    padding: 8px;
    gap: 8px;
  }
  .tile {
    width: 70px;
    height: 70px;
    font-size: 1.2rem;
  }
}