/* ============================================
   Sudoku Game - Complete Stylesheet
   ============================================ */

/* --- Custom Properties --- */

:root {
  --bg-primary: #ffffff;
  --bg-secondary: #f8f8fa;
  --bg-tertiary: #f0f0f2;
  --text-primary: #2C2C2A;
  --text-secondary: #5F5E5A;
  --text-given: #2C2C2A;
  --text-user: #378ADD;
  --border-thin: #d0d0d0;
  --border-thick: #2C2C2A;
  --blue: #378ADD;
  --blue-light: #E6F1FB;
  --blue-strong: #185FA5;
  --red: #E24B4A;
  --red-light: #FCEBEB;
  --teal: #1D9E75;
  --teal-light: #E1F5EE;
  --purple: #7F77DD;
  --purple-light: #EEEDFE;
  --amber: #BA7517;
  --amber-light: #FAEEDA;
  --cell-highlight-same: rgba(55, 138, 221, 0.18);
  --modal-backdrop: rgba(0, 0, 0, 0.5);
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.06);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.1);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg-primary: #1e1e2e;
    --bg-secondary: #12121e;
    --bg-tertiary: #262638;
    --text-primary: #f0f0f0;
    --text-secondary: #b0b0c8;
    --text-given: #ffffff;
    --text-user: #7ec8ff;
    --border-thin: #3e3e5c;
    --border-thick: #a0a0c4;
    --blue-light: rgba(55, 138, 221, 0.28);
    --red-light: rgba(226, 75, 74, 0.3);
    --teal-light: rgba(29, 158, 117, 0.28);
    --purple-light: rgba(127, 119, 221, 0.28);
    --amber-light: rgba(186, 117, 23, 0.28);
    --cell-highlight-same: rgba(55, 138, 221, 0.4);
    --modal-backdrop: rgba(0, 0, 0, 0.75);
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.5);
  }
}

/* --- Reset --- */

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

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: var(--bg-secondary);
  color: var(--text-primary);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  -webkit-tap-highlight-color: transparent;
  overscroll-behavior: none;
  overflow: hidden;
  position: fixed;
  width: 100%;
  height: 100%;
  touch-action: manipulation;
}

button {
  font-family: inherit;
  cursor: pointer;
  border: none;
  background: none;
  color: inherit;
  touch-action: manipulation;
}

select {
  font-family: inherit;
  cursor: pointer;
}

/* --- App Container --- */

.app {
  display: flex;
  flex-direction: column;
  height: 100vh;
  height: 100dvh;
  height: calc(var(--app-height, 100dvh));
  max-width: 500px;
  margin: 0 auto;
  padding: 12px 16px;
  padding-bottom: calc(12px + env(safe-area-inset-bottom, 0px));
  overflow: hidden;
}

/* --- Header --- */

.header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-bottom: 8px;
}

.header-left {
  display: flex;
  align-items: center;
  gap: 8px;
}

.header-right {
  display: flex;
  align-items: center;
  gap: 12px;
}

.difficulty-select {
  appearance: none;
  -webkit-appearance: none;
  background: var(--bg-primary);
  color: var(--text-primary);
  border: 1px solid var(--border-thin);
  border-radius: 20px;
  padding: 6px 28px 6px 12px;
  font-size: 13px;
  font-weight: 600;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='10' height='6'%3E%3Cpath d='M0 0l5 6 5-6z' fill='%235F5E5A'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 10px center;
  outline: none;
  transition: border-color 0.15s;
}

.difficulty-select:focus {
  border-color: var(--blue);
}

.new-game-btn {
  font-size: 13px;
  font-weight: 600;
  color: var(--blue);
  padding: 6px 12px;
  border-radius: 20px;
  border: 1px solid var(--blue);
  background: transparent;
  transition: background 0.15s, color 0.15s;
}

.new-game-btn:hover {
  background: var(--blue);
  color: #fff;
}

.timer {
  font-family: 'SF Mono', 'Menlo', 'Consolas', monospace;
  font-size: 14px;
  font-weight: 500;
  color: var(--text-secondary);
  min-width: 48px;
  text-align: right;
}

.mistakes {
  font-size: 13px;
  font-weight: 500;
  color: var(--text-secondary);
}

.mistakes.at-limit {
  color: var(--red);
  font-weight: 700;
}

.menu-btn {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  width: 36px;
  height: 36px;
  gap: 4px;
  border-radius: 8px;
  transition: background 0.15s;
}

.menu-btn:hover {
  background: var(--bg-tertiary);
}

.menu-btn span {
  display: block;
  width: 18px;
  height: 2px;
  background: var(--text-primary);
  border-radius: 1px;
}

/* --- Board wrapper --- */

.board-wrapper {
  flex: 1 1 0;
  min-height: 0;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 4px 0;
}

/* --- Board --- */

.board {
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  grid-template-rows: repeat(9, 1fr);
  aspect-ratio: 1;
  height: 100%;
  max-height: 450px;
  max-width: min(100%, 450px);
  border: 2px solid var(--border-thick);
  border-radius: 8px;
  overflow: hidden;
  user-select: none;
}

/* --- Cells --- */

.cell {
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: clamp(14px, 4vw, 24px);
  border: 0.5px solid var(--border-thin);
  background: var(--bg-primary);
  position: relative;
  cursor: pointer;
  transition: background 0.1s;
  line-height: 1;
  touch-action: manipulation;
}

/* 3×3 box thick borders */
.cell:nth-child(9n+3),
.cell:nth-child(9n+6) {
  border-right: 2px solid var(--border-thick);
}

.cell:nth-child(n+19):nth-child(-n+27),
.cell:nth-child(n+46):nth-child(-n+54) {
  border-bottom: 2px solid var(--border-thick);
}

/* Cell states */

.cell.given {
  font-weight: 700;
  color: var(--text-given);
}

.cell.user {
  color: var(--text-user);
  font-weight: 500;
}

.cell.selected {
  background: var(--blue-light);
  outline: 2px solid var(--blue);
  outline-offset: -2px;
  z-index: 1;
}

.cell.highlighted {
  background: var(--blue-light);
}

.cell.same-number {
  background: var(--cell-highlight-same);
}

.cell.error {
  background: var(--red-light);
  color: var(--red);
  font-weight: 600;
}

.cell.cant-place {
  background: var(--bg-tertiary);
  cursor: default;
  color: color-mix(in srgb, var(--text-primary) 40%, transparent);
}

/* Hint cell states */

.cell.hint-cell {
  background: var(--purple-light);
  animation: pulse 1.5s ease-in-out infinite;
}

.cell.hint-eliminated {
  background: var(--amber-light);
}

.cell.hint-eliminated .note {
  text-decoration: line-through;
  text-decoration-color: var(--red);
}

.cell.hint-unit {
  background: color-mix(in srgb, var(--purple-light) 40%, var(--bg-primary));
}

/* Notes inside cells */

.cell .notes {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  width: 100%;
  height: 100%;
  padding: 1px;
}

.cell .note {
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: clamp(7px, 1.8vw, 11px);
  color: var(--text-secondary);
  line-height: 1;
}

/* Cell entry animation */

.cell.pop {
  animation: cellPop 0.2s ease-out;
}

/* --- Number Pad --- */

.numpad {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 6px;
  width: min(100%, 450px);
  margin: 8px auto 0;
}

.num-btn {
  position: relative;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 20px;
  font-weight: 600;
  background: var(--bg-primary);
  border: 0.5px solid var(--border-thin);
  border-radius: 8px;
  color: var(--text-primary);
  transition: background 0.1s, color 0.1s;
  padding: 10px 0;
  min-height: 44px;
}

.num-btn:hover {
  background: var(--blue-light);
}

.num-btn:active {
  background: var(--blue);
  color: #fff;
}

.num-btn.active {
  background: var(--blue);
  color: #fff;
}

.num-btn.completed {
  opacity: 0.3;
  pointer-events: none;
}

.num-btn.locked {
  outline: 2.5px solid var(--border-thick);
  outline-offset: -1px;
  background: var(--blue-light);
}

.num-btn .count {
  position: absolute;
  top: 3px;
  right: 5px;
  font-size: 9px;
  font-weight: 500;
  color: var(--text-secondary);
  line-height: 1;
}

.num-btn.active .count {
  color: rgba(255, 255, 255, 0.7);
}

/* --- Toolbar --- */

.toolbar {
  display: flex;
  justify-content: center;
  gap: 16px;
  margin-top: 8px;
}

.tool-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  padding: 8px 12px;
  border-radius: 8px;
  transition: background 0.15s;
  min-width: 44px;
  min-height: 44px;
}

.tool-btn:hover {
  background: var(--bg-tertiary);
}

.tool-btn .tool-icon {
  width: 22px;
  height: 22px;
  display: flex;
  justify-content: center;
  align-items: center;
  color: var(--text-primary);
}

.tool-btn .tool-icon svg {
  width: 100%;
  height: 100%;
  fill: none;
  stroke: currentColor;
  stroke-width: 2;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.tool-btn .tool-label {
  font-size: 11px;
  color: var(--text-secondary);
  white-space: nowrap;
}

.tool-btn.active {
  color: var(--blue);
}

.tool-btn.active .tool-icon {
  color: var(--blue);
}

.tool-btn.active .tool-label {
  color: var(--blue);
  font-weight: 600;
}

/* --- Hint Panel --- */

.hint-panel {
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  background: var(--bg-primary);
  border-top: 2px solid var(--purple);
  padding: 16px;
  z-index: 100;
  animation: slideUp 0.25s ease-out;
  box-shadow: var(--shadow-md);
}

.hint-panel-inner {
  max-width: 500px;
  margin: 0 auto;
}

.hint-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: 8px;
}

.hint-technique {
  font-size: 14px;
  font-weight: 700;
  color: var(--purple);
}

.hint-close {
  width: 28px;
  height: 28px;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 18px;
  border-radius: 50%;
  color: var(--text-secondary);
  transition: background 0.15s;
  flex-shrink: 0;
}

.hint-close:hover {
  background: var(--bg-tertiary);
}

.hint-description {
  font-size: 14px;
  line-height: 1.5;
  color: var(--text-primary);
  margin-bottom: 12px;
}

.hint-apply {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 16px;
  font-size: 13px;
  font-weight: 600;
  color: #fff;
  background: var(--purple);
  border-radius: 20px;
  transition: opacity 0.15s;
}

.hint-apply:hover {
  opacity: 0.85;
}

/* --- Modal --- */

.modal-overlay {
  position: fixed;
  inset: 0;
  background: var(--modal-backdrop);
  display: flex;
  justify-content: center;
  align-items: center;
  z-index: 200;
  animation: fadeIn 0.2s ease-out;
}

.modal {
  background: var(--bg-primary);
  border-radius: 16px;
  padding: 24px;
  max-width: 400px;
  width: 90%;
  animation: fadeIn 0.25s ease-out;
}

.modal-title {
  font-size: 18px;
  font-weight: 700;
  margin-bottom: 16px;
  text-align: center;
}

.modal-actions {
  display: flex;
  gap: 8px;
  margin-top: 20px;
}

.modal-actions button {
  flex: 1;
  padding: 10px;
  font-size: 14px;
  font-weight: 600;
  border-radius: 8px;
  transition: opacity 0.15s;
}

.modal-btn-primary {
  background: var(--blue);
  color: #fff;
}

.modal-btn-primary:hover {
  opacity: 0.85;
}

.modal-btn-secondary {
  background: var(--bg-tertiary);
  color: var(--text-primary);
}

.modal-btn-secondary:hover {
  opacity: 0.8;
}

/* --- Victory Modal --- */

.victory-modal .modal {
  text-align: center;
}

.victory-title {
  font-size: 24px;
  font-weight: 800;
  color: var(--teal);
  margin-bottom: 4px;
}

.victory-subtitle {
  font-size: 14px;
  color: var(--text-secondary);
  margin-bottom: 20px;
}

.victory-stats {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
  margin-bottom: 20px;
}

.stat-card {
  background: var(--bg-secondary);
  border-radius: 10px;
  padding: 12px;
}

.stat-card .stat-value {
  font-size: 20px;
  font-weight: 700;
  color: var(--text-primary);
}

.stat-card .stat-label {
  font-size: 11px;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-top: 2px;
}

.victory-actions {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.victory-actions button {
  width: 100%;
  padding: 12px;
  font-size: 15px;
  font-weight: 600;
  border-radius: 10px;
  transition: opacity 0.15s;
  text-align: center;
}

.victory-btn-primary {
  background: var(--teal);
  color: #fff;
}

.victory-btn-primary:hover {
  opacity: 0.85;
}

.victory-btn-secondary {
  background: var(--bg-tertiary);
  color: var(--text-primary);
}

.victory-btn-secondary:hover {
  opacity: 0.8;
}

/* --- Stats Page --- */

.stats-page {
  position: fixed;
  inset: 0;
  background: var(--bg-secondary);
  z-index: 300;
  overflow-y: auto;
  animation: slideInRight 0.25s ease-out;
  -webkit-overflow-scrolling: touch;
}

.stats-inner {
  max-width: 500px;
  margin: 0 auto;
  padding: 16px;
}

.stats-header {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 20px;
}

.stats-back-btn {
  width: 36px;
  height: 36px;
  display: flex;
  justify-content: center;
  align-items: center;
  border-radius: 8px;
  font-size: 20px;
  transition: background 0.15s;
}

.stats-back-btn:hover {
  background: var(--bg-tertiary);
}

.stats-title {
  font-size: 20px;
  font-weight: 700;
}

.stats-summary {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 10px;
  margin-bottom: 24px;
}

.stats-metric {
  background: var(--bg-primary);
  border-radius: 10px;
  padding: 14px;
}

.stats-metric .metric-value {
  font-size: 22px;
  font-weight: 700;
  color: var(--text-primary);
  line-height: 1.1;
}

.stats-metric .metric-label {
  font-size: 12px;
  color: var(--text-secondary);
  margin-top: 2px;
}

.stats-section-title {
  font-size: 15px;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 12px;
}

.stats-chart-container {
  background: var(--bg-primary);
  border-radius: 10px;
  padding: 16px;
  margin-bottom: 24px;
}

.stats-chart-container canvas {
  width: 100%;
  max-height: 200px;
}

.stats-charts-row {
  display: flex;
  gap: 10px;
  margin-bottom: 24px;
}

.stats-charts-row .stats-chart-container {
  flex: 1;
  min-width: 0;
  margin-bottom: 0;
}

.stats-chart-sublabel {
  font-size: 12px;
  color: var(--text-secondary);
  margin-bottom: 8px;
}

.stats-section-title-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 12px;
}

.stats-section-title-row .stats-section-title {
  margin-bottom: 0;
}

.stats-toggle {
  display: flex;
  gap: 4px;
}

.stats-toggle button {
  font-size: 12px;
  padding: 4px 10px;
  border-radius: 6px;
  color: var(--text-secondary);
  background: var(--bg-primary);
  transition: background 0.15s, color 0.15s;
}

.stats-toggle button.active {
  background: var(--purple);
  color: #fff;
}

.stats-history {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.history-item {
  display: flex;
  align-items: center;
  gap: 10px;
  background: var(--bg-primary);
  border-radius: 10px;
  padding: 12px;
}

.history-item .difficulty-badge {
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  padding: 3px 8px;
  border-radius: 4px;
  flex-shrink: 0;
}

.difficulty-badge.easy {
  background: var(--teal-light);
  color: var(--teal);
}

.difficulty-badge.medium {
  background: var(--blue-light);
  color: var(--blue);
}

.difficulty-badge.hard {
  background: var(--amber-light);
  color: var(--amber);
}

.difficulty-badge.advanced {
  background: var(--red-light);
  color: var(--red);
}

.history-item .history-details {
  flex: 1;
  min-width: 0;
}

.history-item .history-time {
  font-size: 14px;
  font-weight: 600;
}

.history-item .history-status {
  color: var(--text-secondary);
  font-weight: 500;
}

.history-item .history-mistakes {
  font-size: 12px;
  color: var(--text-secondary);
}

.history-item .history-mistake-count {
  font-weight: 700;
}

.history-item .history-mistake-count.has-mistakes {
  color: var(--red);
}

.history-item .history-date {
  font-size: 12px;
  color: var(--text-secondary);
  flex-shrink: 0;
}

/* --- Data Management --- */

.data-management {
  display: flex;
  flex-direction: column;
  gap: 8px;
  margin-bottom: 24px;
}

.data-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 16px;
  font-size: 14px;
  font-weight: 600;
  border-radius: 10px;
  background: var(--bg-primary);
  color: var(--text-primary);
  border: 1px solid var(--border-thin);
  transition: background 0.15s;
}

.data-btn:hover {
  background: var(--bg-tertiary);
}

.data-btn svg {
  flex-shrink: 0;
}

.refresh-app-btn {
  color: var(--red);
}

/* --- Animations --- */

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

@keyframes slideUp {
  from { transform: translateY(100%); }
  to { transform: translateY(0); }
}

@keyframes slideInRight {
  from { transform: translateX(100%); }
  to { transform: translateX(0); }
}

@keyframes pulse {
  0%, 100% { transform: scale(1); }
  50% { transform: scale(1.05); }
}

@keyframes cellPop {
  0% { transform: scale(0.8); }
  50% { transform: scale(1.1); }
  100% { transform: scale(1); }
}

/* --- Responsive --- */

@media (max-width: 360px) {
  .app {
    padding: 10px;
  }

  .header {
    flex-wrap: wrap;
    gap: 8px;
  }

  .header-right {
    gap: 8px;
  }

  .difficulty-select {
    font-size: 12px;
    padding: 5px 24px 5px 10px;
  }

  .new-game-btn {
    font-size: 12px;
    padding: 5px 10px;
  }

  .timer {
    font-size: 13px;
  }

  .mistakes {
    font-size: 12px;
  }

  .numpad {
    gap: 6px;
  }

  .num-btn {
    font-size: 17px;
    border-radius: 6px;
  }

  .toolbar {
    gap: 10px;
  }

  .tool-btn {
    padding: 6px 8px;
  }

  .tool-btn .tool-label {
    font-size: 10px;
  }
}

/* Ensure touch targets on interactive controls */
@media (pointer: coarse) {
  .num-btn {
    min-height: 40px;
  }

  .tool-btn {
    min-width: 44px;
    min-height: 44px;
  }
}

/* Short screens: compact everything */
@media (max-height: 640px) {
  .app {
    padding: 6px 12px;
  }

  .board-wrapper {
    padding: 2px 0;
  }

  .numpad {
    gap: 4px;
    margin-top: 4px;
  }

  .num-btn {
    padding: 6px 0;
    font-size: 17px;
    min-height: 36px;
  }

  .toolbar {
    margin-top: 4px;
    gap: 12px;
  }

  .tool-btn {
    padding: 4px 8px;
    min-height: 36px;
  }

  .tool-btn .tool-label {
    font-size: 10px;
  }
}

/* Utility: visually hidden but accessible */
.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;
}