:root {
  color-scheme: dark;
  --bg: #12131a;
  --panel: #1c1e29;
  --cell: #262939;
  --accent: #5eead4;
  --accent-2: #f472b6;
  --text: #e6e7ee;
  --text-dim: #8a8da3;

  /* Colores por valor de ficha, mismo espíritu que la paleta clásica de 2048
     pero adaptados al tema oscuro del resto del sitio. */
  --t2: #3a3d52;
  --t4: #454969;
  --t8: #f2b179;
  --t16: #f59563;
  --t32: #f67c5f;
  --t64: #f65e3b;
  --t128: #edcf72;
  --t256: #edcc61;
  --t512: #edc850;
  --t1024: #edc53f;
  --t2048: #edc22e;
  --thi: var(--accent-2);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  min-height: 100dvh;
  display: flex;
  align-items: center;
  justify-content: center;
  background: radial-gradient(circle at 50% 0%, #1e2130, var(--bg));
  font-family: "Segoe UI", system-ui, sans-serif;
  color: var(--text);
  overflow: hidden;
}

.app {
  position: relative;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: clamp(0.5rem, 2vmin, 1rem);
  padding: clamp(0.75rem, 3vmin, 1.5rem);
  width: min(480px, 92vmin, 95vw);
}

h1 {
  margin: 0;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  font-size: clamp(1.1rem, 5.5vmin, 1.6rem);
  color: var(--accent);
}

.hud {
  display: flex;
  width: 100%;
  justify-content: space-between;
  background: var(--panel);
  border-radius: 12px;
  padding: clamp(0.4rem, 2vmin, 0.75rem) clamp(0.5rem, 2.5vmin, 1rem);
}

.hud-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.15rem;
  flex: 1;
}

.hud-label {
  font-size: clamp(0.55rem, 1.8vmin, 0.7rem);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-dim);
}

.hud-value {
  font-size: clamp(0.85rem, 3vmin, 1.1rem);
  font-weight: 600;
}

.board-wrap {
  position: relative;
  width: 100%;
  aspect-ratio: 1 / 1;
  touch-action: none;
  user-select: none;
  -webkit-tap-highlight-color: transparent;
}

.board-bg,
.board {
  position: absolute;
  inset: 0;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-template-rows: repeat(4, 1fr);
  gap: clamp(6px, 2vmin, 12px);
  background: var(--panel);
  padding: clamp(6px, 2.2vmin, 12px);
  border-radius: 16px;
}

.board-bg-cell {
  border-radius: 8px;
  background: var(--cell);
}

.board {
  background: transparent;
  pointer-events: none;
}

.tile {
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 8px;
  background: var(--t2);
  color: var(--text);
  font-weight: 700;
  font-size: clamp(1rem, 6vmin, 1.7rem);
}

.tile.new {
  animation: pop-in 0.15s ease-out;
}

.tile[data-value="4"] { background: var(--t4); }
.tile[data-value="8"] { background: var(--t8); color: #2b1a0e; }
.tile[data-value="16"] { background: var(--t16); color: #2b1a0e; }
.tile[data-value="32"] { background: var(--t32); color: #2b1a0e; }
.tile[data-value="64"] { background: var(--t64); color: #fff; }
.tile[data-value="128"] { background: var(--t128); color: #2b1a0e; font-size: clamp(0.9rem, 5.2vmin, 1.5rem); }
.tile[data-value="256"] { background: var(--t256); color: #2b1a0e; font-size: clamp(0.9rem, 5.2vmin, 1.5rem); }
.tile[data-value="512"] { background: var(--t512); color: #2b1a0e; font-size: clamp(0.9rem, 5.2vmin, 1.5rem); }
.tile[data-value="1024"] { background: var(--t1024); color: #2b1a0e; font-size: clamp(0.75rem, 4.6vmin, 1.3rem); }
.tile[data-value="2048"] { background: var(--t2048); color: #2b1a0e; font-size: clamp(0.75rem, 4.6vmin, 1.3rem); box-shadow: 0 0 18px 2px rgba(237, 194, 46, 0.6); }
.tile[data-hi="1"] { background: var(--thi); color: #2b0f22; font-size: clamp(0.7rem, 4.2vmin, 1.2rem); }

.tile.merged {
  animation: pop-merge 0.15s ease-out;
}

@keyframes pop-in {
  from { transform: scale(0.4); opacity: 0; }
  to { transform: scale(1); opacity: 1; }
}

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

.win-banner {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.75rem;
  background: rgba(10, 11, 16, 0.75);
  border-radius: 16px;
  font-size: clamp(1rem, 4vmin, 1.3rem);
  font-weight: 700;
  color: var(--t2048);
  text-align: center;
  padding: 1rem;
}

.win-banner.hidden {
  display: none;
}

.win-banner button {
  padding: 0.5rem 1rem;
  border: none;
  border-radius: 8px;
  background: var(--accent);
  color: #08221d;
  font-weight: 700;
  cursor: pointer;
}

.overlay {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(10, 11, 16, 0.75);
  border-radius: 16px;
}

.overlay.hidden {
  display: none;
}

.overlay-card {
  background: var(--panel);
  border-radius: 14px;
  padding: 1.5rem;
  width: min(420px, 85vw);
  max-height: 90vh;
  overflow-y: auto;
  text-align: center;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.overlay-card h2 {
  margin: 0;
  color: var(--accent);
}

.overlay-card p {
  margin: 0;
  color: var(--text-dim);
  font-size: 0.9rem;
  line-height: 1.4;
}

.auth-box {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.auth-buttons {
  display: flex;
  gap: 0.5rem;
  justify-content: center;
}

.auth-btn {
  padding: 0.45rem 0.9rem;
  border: none;
  border-radius: 8px;
  font-weight: 600;
  font-size: 0.85rem;
  cursor: pointer;
  transition: transform 0.1s ease;
}

.auth-btn:hover {
  transform: translateY(-1px);
}

.auth-btn-primary {
  background: var(--accent);
  color: #08221d;
}

.auth-btn-secondary {
  background: var(--cell);
  color: var(--text);
}

.auth-user {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  gap: 0.5rem 0.75rem;
  background: var(--cell);
  border-radius: 10px;
  padding: 0.5rem 0.75rem;
  font-size: 0.85rem;
}

.auth-username {
  font-weight: 600;
}

.auth-coins {
  color: var(--accent);
  font-weight: 600;
}

.auth-link-btn {
  background: none;
  border: none;
  color: var(--text-dim);
  font-size: 0.8rem;
  text-decoration: underline;
  cursor: pointer;
  padding: 0;
}

.auth-form {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  text-align: left;
}

.auth-form input {
  background: var(--cell);
  border: 1px solid #1a1b24;
  border-radius: 8px;
  padding: 0.5rem 0.6rem;
  color: var(--text);
  font-size: 0.9rem;
}

.auth-form input:focus {
  outline: 1px solid var(--accent);
}

.auth-form-error {
  margin: 0;
  color: #ef4444;
  font-size: 0.8rem;
  min-height: 1em;
}

.auth-form-actions {
  display: flex;
  gap: 0.5rem;
}

.auth-form-actions .auth-btn {
  flex: 1;
}

.auth-switch {
  margin: 0;
  font-size: 0.8rem;
  text-align: center;
}

.auth-switch a {
  color: var(--accent);
}

.reward-text {
  margin: 0;
  color: var(--accent);
  font-weight: 700;
}

.reward-text.hidden {
  display: none;
}

#start-btn {
  margin-top: 0.5rem;
  padding: 0.6rem 1.2rem;
  border: none;
  border-radius: 8px;
  background: var(--accent);
  color: #08221d;
  font-weight: 700;
  font-size: 1rem;
  cursor: pointer;
  transition: transform 0.1s ease;
}

#start-btn:hover {
  transform: translateY(-1px);
}

.back-btn {
  margin-top: 0.25rem;
  padding: 0.5rem 1.1rem;
  border-radius: 8px;
  background: var(--cell);
  color: var(--text);
  font-weight: 600;
  font-size: 0.9rem;
  text-decoration: none;
  transition: transform 0.1s ease;
}

.back-btn:hover {
  transform: translateY(-1px);
}

.back-btn.hidden {
  display: none;
}

.leaderboard-box {
  margin-top: 0.5rem;
  padding-top: 0.75rem;
  border-top: 1px solid #1a1b24;
}

.leaderboard-box h3 {
  margin: 0 0 0.5rem;
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-dim);
}

.leaderboard-list {
  list-style: none;
  counter-reset: leaderboard;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
  max-height: 220px;
  overflow-y: auto;
}

.leaderboard-list li {
  counter-increment: leaderboard;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  background: var(--cell);
  border-radius: 8px;
  padding: 0.35rem 0.6rem;
  font-size: 0.85rem;
}

.leaderboard-list li::before {
  content: counter(leaderboard);
  flex: 0 0 auto;
  width: 1.4em;
  color: var(--text-dim);
  font-weight: 700;
  text-align: right;
}

.leaderboard-name {
  flex: 1;
  text-align: left;
  font-weight: 600;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.leaderboard-score {
  color: var(--accent);
  font-weight: 700;
}

.leaderboard-tile {
  color: var(--text-dim);
  font-size: 0.8rem;
}

.leaderboard-empty {
  color: var(--text-dim);
  font-size: 0.85rem;
  text-align: center;
  background: none !important;
}