/* Sanscript Sudoku — visual polish + theme (WU-6) */

/* ------------------------------------------------------------------
   Design tokens
   ------------------------------------------------------------------ */
:root {
  --color-bg: #fafbfc;
  --color-surface: #fff;
  --color-text: #1f2328;
  --color-text-secondary: #656d76;
  --color-border: #d0d7de;
  --color-border-strong: #1f2328;
  --color-accent: #0969da;
  --color-accent-soft: #ddf4ff;
  --color-peer: #f3f4f6;
  --color-same: #e0f2fe;
  --color-conflict: #ffebe9;
  --color-conflict-text: #cf222e;
  --color-clue: #1f2328;
  --color-user: #0969da;
  --color-success: #1a7f37;
  --radius: 0.5rem;
  --shadow-sm: 0 1px 2px rgb(31 35 40 / 4%);
  --shadow-md: 0 4px 12px rgb(31 35 40 / 8%);
  --transition: 150ms cubic-bezier(0.4, 0, 0.2, 1);
}

@media (prefers-color-scheme: dark) {
  :root {
    --color-bg: #0d1117;
    --color-surface: #161b22;
    --color-text: #c9d1d9;
    --color-text-secondary: #8b949e;
    --color-border: #30363d;
    --color-border-strong: #c9d1d9;
    --color-accent: #58a6ff;
    --color-accent-soft: #0c2d6b;
    --color-peer: #21262d;
    --color-same: #0d2f5c;
    --color-conflict: #3d1515;
    --color-conflict-text: #f85149;
    --color-clue: #c9d1d9;
    --color-user: #58a6ff;
    --color-success: #3fb950;
    --shadow-sm: 0 1px 2px rgb(0 0 0 / 30%);
    --shadow-md: 0 4px 12px rgb(0 0 0 / 40%);
  }
}

/* Screen-reader only */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* ------------------------------------------------------------------
   Base
   ------------------------------------------------------------------ */
*, *::before, *::after {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: Inter, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  line-height: 1.5;
  background-color: var(--color-bg);
  color: var(--color-text);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

header, footer {
  text-align: center;
  padding: 1.25rem 1rem;
}

header h1 {
  margin: 0;
  font-size: clamp(1.25rem, 4vw, 1.75rem);
  font-weight: 700;
  letter-spacing: -0.02em;
}

main {
  max-width: 28rem;
  margin: 0 auto;
  padding: 0 1rem 2rem;
}

/* ------------------------------------------------------------------
   Board
   ------------------------------------------------------------------ */
.board-section {
  display: flex;
  justify-content: center;
  margin-bottom: 1.25rem;
}

#board {
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  grid-template-rows: repeat(9, 1fr);
  width: 100%;
  max-width: 22rem;
  aspect-ratio: 1 / 1;
  border: 2px solid var(--color-border-strong);
  border-radius: calc(var(--radius) / 2);
  overflow: hidden;
  background-color: var(--color-surface);
  box-shadow: var(--shadow-md);
}

#board .cell {
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: clamp(0.875rem, 3.8vw, 1.375rem);
  font-weight: 500;
  border-right: 1px solid var(--color-border);
  border-bottom: 1px solid var(--color-border);
  background-color: var(--color-surface);
  cursor: pointer;
  user-select: none;
  transition: background-color var(--transition), transform var(--transition);
}

#board .cell:hover {
  background-color: var(--color-peer);
  transform: scale(1.04);
  z-index: 2;
}

/* Remove outer cell borders so container border is the only edge */
#board .cell:nth-child(9n) {
  border-right-width: 0;
}

#board .cell:nth-child(n+73) {
  border-bottom-width: 0;
}

/* 3×3 box dividers — uniform 2px */
#board .cell:nth-child(3n) {
  border-right-width: 2px;
  border-right-color: var(--color-border-strong);
}

#board .cell:nth-child(n+19):nth-child(-n+27),
#board .cell:nth-child(n+46):nth-child(-n+54) {
  border-bottom-width: 2px;
  border-bottom-color: var(--color-border-strong);
}

/* Selected cell */
#board .cell.selected {
  background-color: var(--color-accent-soft);
  outline: 2px solid var(--color-accent);
  outline-offset: -2px;
  z-index: 1;
}

/* Peer highlight */
#board .cell.peer {
  background-color: var(--color-peer);
}

/* Same-value highlight */
#board .cell.same-value {
  background-color: var(--color-same);
}

/* Conflict highlight */
#board .cell.conflict {
  background-color: var(--color-conflict);
  color: var(--color-conflict-text);
}

/* Notes mini-grid */
#board .cell.has-notes {
  padding: 0;
}

.notes-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  width: 100%;
  height: 100%;
  align-items: center;
  justify-items: center;
}

.note-digit {
  font-size: clamp(0.375rem, 1.6vw, 0.625rem);
  font-weight: 600;
  color: var(--color-text-secondary);
  line-height: 1;
}

/* Clue vs user-input */
#board .cell.clue {
  font-weight: 700;
  color: var(--color-clue);
}

#board .cell.user-input {
  color: var(--color-user);
}

/* ------------------------------------------------------------------
   Number palette
   ------------------------------------------------------------------ */
.palette-section {
  margin-bottom: 1.25rem;
}

.palette {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.5rem;
}

.palette button {
  min-width: 2.5rem;
  padding: 0.5rem 0.75rem;
  font-size: 1rem;
  font-weight: 600;
  font-family: inherit;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background-color: var(--color-surface);
  color: var(--color-text);
  cursor: pointer;
  box-shadow: var(--shadow-sm);
  transition: background-color var(--transition), border-color var(--transition), transform var(--transition);
}

/* stylelint-disable-next-line no-descending-specificity */
.palette button:hover {
  background-color: var(--color-peer);
  border-color: var(--color-border-strong);
  transform: translateY(-1px);
}

.palette button:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
}

.palette button:active {
  transform: translateY(0);
}

/* ------------------------------------------------------------------
   Status
   ------------------------------------------------------------------ */
.status-section {
  text-align: center;
  margin-bottom: 1.25rem;
}

.status-row {
  display: flex;
  justify-content: center;
  gap: 1rem;
  margin: 0;
  font-weight: 600;
  font-size: 0.9375rem;
}

#result {
  color: var(--color-success);
}

/* ------------------------------------------------------------------
   Action buttons
   ------------------------------------------------------------------ */
.action-section {
  display: flex;
  justify-content: center;
  gap: 0.75rem;
}

.action-section button {
  padding: 0.5rem 1rem;
  font-size: 0.9375rem;
  font-weight: 500;
  font-family: inherit;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background-color: var(--color-surface);
  color: var(--color-text);
  cursor: pointer;
  box-shadow: var(--shadow-sm);
  transition: background-color var(--transition), border-color var(--transition), transform var(--transition);
}

.action-section button:hover {
  background-color: var(--color-peer);
  border-color: var(--color-border-strong);
  transform: translateY(-1px);
}

.action-section button:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
}

.action-section button:active {
  transform: translateY(0);
}

/* ------------------------------------------------------------------
   Game controls
   ------------------------------------------------------------------ */
.game-controls {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  gap: 0.75rem;
  margin-bottom: 1.25rem;
}

.game-controls label {
  font-weight: 600;
  font-size: 0.875rem;
  color: var(--color-text-secondary);
}

.game-controls select,
.game-controls button {
  padding: 0.5rem 0.875rem;
  font-size: 0.9375rem;
  font-weight: 500;
  font-family: inherit;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background-color: var(--color-surface);
  color: var(--color-text);
  cursor: pointer;
  box-shadow: var(--shadow-sm);
  transition: border-color var(--transition), background-color var(--transition), transform var(--transition);
}

/* stylelint-disable-next-line no-descending-specificity */
.game-controls select:hover,
/* stylelint-disable-next-line no-descending-specificity */
.game-controls button:hover {
  border-color: var(--color-border-strong);
}

.game-controls select:focus-visible,
.game-controls button:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
}

.game-controls button.active {
  background-color: var(--color-accent-soft);
  border-color: var(--color-accent);
  color: var(--color-accent);
}

.game-controls button:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.toggle-group {
  display: flex;
  align-items: center;
  gap: 0.375rem;
}

.toggle-group input[type="checkbox"] {
  width: 1rem;
  height: 1rem;
  accent-color: var(--color-accent);
  cursor: pointer;
}

/* ------------------------------------------------------------------
   Footer
   ------------------------------------------------------------------ */
footer p {
  margin: 0;
  font-size: 0.875rem;
  color: var(--color-text-secondary);
}

/* ------------------------------------------------------------------
   Responsive — 320px minimum
   ------------------------------------------------------------------ */
@media (width <= 360px) {
  main {
    padding: 0 0.5rem 1.5rem;
  }

  .game-controls {
    gap: 0.5rem;
  }

  .game-controls select,
  .game-controls button {
    padding: 0.375rem 0.625rem;
    font-size: 0.875rem;
  }

  #board {
    max-width: 100%;
  }

  .palette button {
    min-width: 2.25rem;
    padding: 0.375rem 0.5rem;
    font-size: 0.9375rem;
  }

  .action-section button {
    padding: 0.375rem 0.75rem;
    font-size: 0.875rem;
  }
}

/* ------------------------------------------------------------------
   Print stylesheet
   ------------------------------------------------------------------ */
@media print {
  body {
    background: #fff;
    color: #000;
  }

  header,
  .game-controls,
  .palette-section,
  .action-section,
  footer {
    display: none;
  }

  main {
    max-width: none;
    padding: 0;
  }

  .board-section {
    margin: 0;
  }

  #board {
    max-width: 16cm;
    box-shadow: none;
    border-color: #000;
    border-radius: 0;
  }

  #board .cell {
    border-color: #888;
    background: #fff;
    color: #000;
  }

  #board .cell.clue {
    font-weight: 700;
  }

  #board .cell.user-input {
    color: #000;
  }

  .status-section {
    margin-top: 0.5rem;
    text-align: center;
  }

  #result {
    color: #000;
  }
}