.game-back {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  min-height: 44px;
  margin-bottom: 20px;
  padding: 8px 14px;
  background: var(--xin-surface);
  border: 1px solid var(--xin-tint-line);
  border-radius: 8px;
  color: var(--xin-blue-dk);
  font-size: 14px;
  font-weight: 550;
  text-decoration: none;
}

.game-back:hover {
  background: var(--xin-tint);
  border-color: var(--xin-blue);
}

.game-back:focus-visible {
  outline: 2px solid var(--xin-blue);
  outline-offset: 3px;
}

.ark-board-wrap,
.game-stage {
  margin-top: 0;
}

.ark-board {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 9px;
  padding: 9px;
  background: #c9d4e6;
  border-radius: 10px;
  user-select: none;
}
.ark-board:focus-visible {
  outline: 2px solid var(--xin-blue);
  outline-offset: 3px;
}

.game-controls {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  gap: 12px 18px;
  margin-top: 20px;
  font-size: 14px;
  color: var(--xin-ink);
}

.game-controls span {
  white-space: nowrap;
}

.game-controls kbd {
  display: inline-block;
  min-width: 26px;
  padding: 3px 6px;
  font-size: 14px;
  font-weight: 550;
  line-height: 1.4;
  border-color: var(--xin-tint-line);
}

@media (max-width: 480px) {
  .game-controls span:first-child {
    flex-basis: 100%;
  }
}

.ark-cell {
  position: relative;
  aspect-ratio: 1;
  background: #dde5f1;
  border-radius: 7px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 650;
  font-size: clamp(18px, 6.2vw, 30px);
  color: var(--xin-ink);
}

.ark-cell[data-v="2"] {
  background: var(--xin-tint);
}
.ark-cell[data-v="4"] {
  background: #dce7f7;
}
.ark-cell[data-v="8"] {
  background: #b9d2f0;
}
.ark-cell[data-v="16"] {
  background: #8fb8e6;
}
.ark-cell[data-v="32"] {
  background: #7ebae4;
  color: #0e2338;
}
.ark-cell[data-v="64"] {
  background: #5277c3;
  color: #fff;
}
.ark-cell[data-v="128"] {
  background: #4763ae;
  color: #fff;
  font-size: clamp(16px, 5.4vw, 26px);
}
.ark-cell[data-v="256"] {
  background: #5e5ba8;
  color: #fff;
  font-size: clamp(16px, 5.4vw, 26px);
}
.ark-cell[data-v="512"] {
  background: #7a519b;
  color: #fff;
  font-size: clamp(16px, 5.4vw, 26px);
}
.ark-cell[data-v="1024"] {
  background: #a34c7e;
  color: #fff;
  font-size: clamp(13px, 4.4vw, 21px);
}
.ark-cell[data-v="2048"] {
  background: #c4643f;
  color: #fff;
  font-size: clamp(13px, 4.4vw, 21px);
  box-shadow: 0 0 0 3px rgba(196, 100, 63, 0.28);
}
.ark-cell.is-big {
  font-size: clamp(12px, 3.8vw, 18px);
}

.ark-cell.is-new {
  animation: ark-appear 0.16s ease-out;
}
.ark-cell.is-merged {
  animation: ark-pop 0.16s ease-out;
}

@keyframes ark-appear {
  from {
    transform: scale(0.4);
    opacity: 0;
  }
  to {
    transform: scale(1);
    opacity: 1;
  }
}
@keyframes ark-pop {
  0% {
    transform: scale(1);
  }
  55% {
    transform: scale(1.14);
  }
  100% {
    transform: scale(1);
  }
}

@media (prefers-reduced-motion: reduce) {
  .ark-cell.is-new,
  .ark-cell.is-merged {
    animation: none;
  }
}

.game-overlay.is-game-over {
  background: rgba(22, 32, 46, 0.94);
  color: #fff;
}

.is-game-over .game-overlay-title {
  font-size: clamp(24px, 5vw, 32px);
}

.is-game-over .game-overlay-text,
.game-over-hint {
  color: var(--xin-line);
}

.game-over-scores {
  display: flex;
  gap: 12px;
  margin: 8px 0;
  color: var(--xin-ink);
}

.game-over-scores[hidden] {
  display: none;
}

.game-over-scores .game-score-value {
  font-size: 28px;
}

.game-over-hint {
  margin: 0 0 10px;
  font-size: 13px;
}

.game-over-hint kbd {
  color: var(--xin-ink);
}