@import url('https://fonts.googleapis.com/css2?family=Space+Mono:wght@400;700&family=Outfit:wght@300;400;600;800;900&display=swap');

:root {
  --bg: #0f0e17;
  --surface: #1a1826;
  --surface2: #252336;
  --accent: #ff6b35;
  --accent2: #f7c59f;
  --gold: #ffd700;
  --text: #fffffe;
  --text-muted: #a7a9be;
  --border: rgba(255,255,255,0.07);
  --cell-empty: #1e1c2e;
  --shadow: 0 20px 60px rgba(0,0,0,0.5);
  --radius: 16px;
}

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

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

body::before {
  content: '';
  position: fixed;
  top: -50%;
  left: -50%;
  width: 200%;
  height: 200%;
  background: radial-gradient(ellipse at 70% 20%, rgba(255,107,53,0.08) 0%, transparent 50%),
              radial-gradient(ellipse at 20% 80%, rgba(99,102,241,0.06) 0%, transparent 50%);
  pointer-events: none;
  z-index: 0;
}

/* ── AUTH ── */
.auth-wrapper {
  position: fixed;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 100;
  background: var(--bg);
  padding: 20px;
}

.auth-box {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 24px;
  padding: 48px 40px;
  width: 100%;
  max-width: 380px;
  box-shadow: var(--shadow);
  text-align: center;
}

.auth-logo {
  font-family: 'Space Mono', monospace;
  font-size: 48px;
  font-weight: 700;
  background: linear-gradient(135deg, var(--accent), var(--gold));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 8px;
}

.auth-subtitle {
  color: var(--text-muted);
  font-size: 14px;
  margin-bottom: 36px;
  font-weight: 300;
}

.auth-box input {
  display: block;
  width: 100%;
  background: var(--surface2);
  border: 1px solid var(--border);
  border-radius: 12px;
  color: var(--text);
  font-family: 'Outfit', sans-serif;
  font-size: 15px;
  padding: 14px 18px;
  margin-bottom: 12px;
  outline: none;
  transition: border-color 0.2s;
}

.auth-box input:focus {
  border-color: var(--accent);
}

.auth-box input::placeholder { color: var(--text-muted); }

.btn-primary {
  width: 100%;
  padding: 14px;
  background: linear-gradient(135deg, var(--accent), #ff8c5a);
  border: none;
  border-radius: 12px;
  color: white;
  font-family: 'Outfit', sans-serif;
  font-size: 16px;
  font-weight: 700;
  cursor: pointer;
  margin-bottom: 10px;
  transition: transform 0.15s, box-shadow 0.15s;
  letter-spacing: 0.5px;
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(255,107,53,0.35);
}

.btn-secondary {
  width: 100%;
  padding: 14px;
  background: transparent;
  border: 1px solid var(--border);
  border-radius: 12px;
  color: var(--text-muted);
  font-family: 'Outfit', sans-serif;
  font-size: 15px;
  font-weight: 500;
  cursor: pointer;
  transition: border-color 0.2s, color 0.2s;
}

.btn-secondary:hover {
  border-color: var(--accent);
  color: var(--accent);
}

/* ── GAME ── */
#gamePage {
  width: 100%;
  max-width: 480px;
  padding: 24px 16px 32px;
  position: relative;
  z-index: 1;
  display: none;
}

.top-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 20px;
}

.game-title {
  font-family: 'Space Mono', monospace;
  font-size: 32px;
  font-weight: 700;
  background: linear-gradient(135deg, var(--accent), var(--gold));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.top-actions {
  display: flex;
  gap: 8px;
}

.icon-btn {
  width: 40px;
  height: 40px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  color: var(--text-muted);
  font-size: 18px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: border-color 0.2s, color 0.2s;
}

.icon-btn:hover {
  border-color: var(--accent);
  color: var(--accent);
}

/* Scores */
.scores-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-bottom: 16px;
}

.score-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px 18px;
  text-align: center;
}

.score-label {
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 1.5px;
  text-transform: uppercase;
  color: var(--text-muted);
  margin-bottom: 4px;
}

.score-value {
  font-family: 'Space Mono', monospace;
  font-size: 22px;
  font-weight: 700;
  color: var(--text);
}

#highScore .score-value {
  color: var(--gold);
}

/* Restart */
.restart-btn {
  width: 100%;
  padding: 12px;
  background: var(--surface2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--text);
  font-family: 'Outfit', sans-serif;
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  margin-bottom: 16px;
  transition: background 0.2s, border-color 0.2s;
  letter-spacing: 0.5px;
}

.restart-btn:hover {
  background: var(--accent);
  border-color: var(--accent);
}

/* Grid */
.grid-wrapper {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 20px;
  padding: 12px;
  box-shadow: var(--shadow);
}

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

.cell {
  aspect-ratio: 1;
  background: var(--cell-empty);
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: 'Space Mono', monospace;
  font-weight: 700;
  font-size: clamp(16px, 4vw, 26px);
  transition: transform 0.1s, background 0.1s;
  position: relative;
  overflow: hidden;
}

.cell.pop {
  animation: pop 0.15s ease;
}

@keyframes pop {
  0% { transform: scale(1); }
  50% { transform: scale(1.12); }
  100% { transform: scale(1); }
}

/* Tile colors */
.cell[data-value="2"]    { background: #2d2b4e; color: #c8c6e8; }
.cell[data-value="4"]    { background: #3a2e5c; color: #d4a8f0; }
.cell[data-value="8"]    { background: #ff6b35; color: #fff; }
.cell[data-value="16"]   { background: #ff8c5a; color: #fff; }
.cell[data-value="32"]   { background: #ff5252; color: #fff; }
.cell[data-value="64"]   { background: #e53935; color: #fff; }
.cell[data-value="128"]  { background: #ffd700; color: #1a1a1a; font-size: clamp(13px, 3.5vw, 22px); }
.cell[data-value="256"]  { background: #ffc107; color: #1a1a1a; font-size: clamp(12px, 3vw, 20px); }
.cell[data-value="512"]  { background: #ff9800; color: #1a1a1a; font-size: clamp(12px, 3vw, 20px); }
.cell[data-value="1024"] { background: #7c4dff; color: #fff; font-size: clamp(10px, 2.5vw, 17px); }
.cell[data-value="2048"] { background: linear-gradient(135deg, #ffd700, #ff6b35); color: #fff; font-size: clamp(10px, 2.5vw, 17px); box-shadow: 0 0 24px rgba(255,215,0,0.5); }

/* Touch controls */
.touch-controls {
  display: grid;
  grid-template-columns: repeat(3, 56px);
  grid-template-rows: repeat(2, 56px);
  gap: 8px;
  justify-content: center;
  margin-top: 20px;
}

.touch-btn {
  width: 56px;
  height: 56px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  color: var(--text);
  font-size: 22px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background 0.15s, transform 0.1s;
  -webkit-tap-highlight-color: transparent;
  user-select: none;
}

.touch-btn:active {
  background: var(--accent);
  transform: scale(0.92);
}

.touch-btn.up    { grid-column: 2; grid-row: 1; }
.touch-btn.left  { grid-column: 1; grid-row: 2; }
.touch-btn.down  { grid-column: 2; grid-row: 2; }
.touch-btn.right { grid-column: 3; grid-row: 2; }

/* Footer */
footer {
  text-align: center;
  padding: 20px;
  color: var(--text-muted);
  font-size: 13px;
  position: relative;
  z-index: 1;
}

footer a {
  color: var(--text-muted);
  text-decoration: none;
  margin: 0 8px;
  transition: color 0.2s;
}

footer a:hover { color: var(--accent); }

/* Game Over overlay */
.game-over-overlay {
  display: none;
  position: absolute;
  inset: 0;
  background: rgba(15,14,23,0.88);
  border-radius: 20px;
  z-index: 10;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 16px;
}

.game-over-overlay.show { display: flex; }

.game-over-title {
  font-family: 'Space Mono', monospace;
  font-size: 36px;
  font-weight: 700;
  color: var(--accent);
}

.game-over-score {
  font-size: 18px;
  color: var(--text-muted);
}

/* Light mode */
body.light {
  --bg: #f5f3ef;
  --surface: #ffffff;
  --surface2: #f0ede8;
  --text: #1a1826;
  --text-muted: #7a7a8c;
  --border: rgba(0,0,0,0.1);
  --cell-empty: #e8e4df;
}

/* Responsive */
@media (max-width: 400px) {
  .auth-box { padding: 32px 24px; }
  .game-title { font-size: 26px; }
}