.sudoku-shell-page::before {
  content: "";
  position: fixed;
  inset: 0;
  z-index: -1;
  background:
    radial-gradient(circle at 0% 10%, rgba(120, 212, 189, 0.18), transparent 30%),
    radial-gradient(circle at 100% 0%, rgba(255, 201, 90, 0.2), transparent 28%),
    linear-gradient(180deg, rgba(242, 234, 223, 0.88) 0%, rgba(217, 233, 248, 0.88) 100%);
}

.sudoku-stage-card {
  padding: 12px;
  border-radius: 30px;
}

.sudoku-toolbar {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
}

.sudoku-select-wrap {
  display: grid;
  gap: 6px;
  min-height: 48px;
  padding: 10px 14px;
  border-radius: 18px;
  background: rgba(255, 255, 255, 0.82);
  border: 1px solid rgba(58, 42, 27, 0.08);
}

.sudoku-select {
  border: none;
  background: transparent;
  color: var(--moyu-ink);
  font: inherit;
  font-weight: 700;
}

.sudoku-status {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
  margin-top: 12px;
}

.sudoku-board-wrap {
  display: grid;
  place-items: center;
  margin-top: 12px;
  padding: 8px;
}

.sudoku-board {
  width: 100%;
  max-width: 420px;
  aspect-ratio: 1;
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  grid-template-rows: repeat(9, 1fr);
  border: 3px solid rgba(43, 33, 24, 0.9);
  border-radius: 20px;
  overflow: hidden;
  background: rgba(255, 255, 255, 0.94);
}

.sudoku-cell {
  border: none;
  border-right: 1px solid rgba(43, 33, 24, 0.22);
  border-bottom: 1px solid rgba(43, 33, 24, 0.22);
  background: rgba(255, 255, 255, 0.9);
  color: var(--moyu-dark);
  font: 700 clamp(1rem, 5vw, 1.4rem) "Segoe UI", "PingFang SC", sans-serif;
}

.sudoku-cell.given { background: rgba(243, 238, 231, 0.96); }
.sudoku-cell.selected { background: rgba(255, 201, 90, 0.3); }
.sudoku-cell.related { background: rgba(121, 183, 255, 0.16); }
.sudoku-cell.match { background: rgba(120, 212, 189, 0.2); }
.sudoku-cell.error { background: rgba(238, 102, 117, 0.2); }
.sudoku-cell.thick-right { border-right: 3px solid rgba(43, 33, 24, 0.84); }
.sudoku-cell.thick-bottom { border-bottom: 3px solid rgba(43, 33, 24, 0.84); }

.sudoku-pad {
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: 10px;
  margin-top: 14px;
}

.sudoku-num.active {
  background: linear-gradient(135deg, rgba(255, 201, 90, 0.94), rgba(244, 124, 56, 0.92));
  color: #fff;
}

.sudoku-message {
  margin: 14px 0 0;
  min-height: 24px;
  color: var(--moyu-muted);
  line-height: 1.55;
}

.sudoku-cell.hint {
  background: rgba(255, 201, 90, 0.38);
  animation: hintFlash 0.85s ease;
}

@keyframes hintFlash {
  0% { transform: scale(1); }
  40% { transform: scale(1.04); }
  100% { transform: scale(1); }
}

@media (max-width: 430px) {
  .sudoku-stage-card {
    padding: 10px;
    border-radius: 24px;
  }

  .sudoku-toolbar,
  .sudoku-status,
  .sudoku-pad {
    gap: 8px;
  }

  .sudoku-select-wrap {
    padding: 9px 12px;
    border-radius: 16px;
  }

  .sudoku-board-wrap {
    margin-top: 10px;
    padding: 4px;
  }

  .sudoku-board {
    border-radius: 16px;
  }

  .sudoku-cell {
    font-size: clamp(0.92rem, 4.5vw, 1.2rem);
  }
}