:root {
  --bg: #faf8f4;
  --surface: #ffffff;
  --box-tint: #f6f2ea;
  --ink: #211f1c;
  --ink-soft: #6b6560;
  --border: #e4dfd6;
  --accent: #b54a2c;
  --accent-soft: #f3ddd2;
  --user-digit: #2a61bb;
  --error: #b23a3a;
  --error-soft: #f6dede;
  --easy: #3f7a5c;
  --medium: #b8862f;
  --hard: #b54a2c;
  --expert: #6b3f63;
  --shadow: 0 8px 24px rgba(33, 31, 28, 0.08);
  --overlay-scrim: rgba(33, 31, 28, 0.4);

  --font-display: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
    Helvetica, Arial, sans-serif;
  --font-ui: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica,
    Arial, sans-serif;
}

:root.dark {
  --bg: #17150f;
  --surface: #211e18;
  --box-tint: #262319;
  --ink: #f3efe9;
  --ink-soft: #a39c8f;
  --border: #3a3527;
  --accent: #dd8a5e;
  --accent-soft: #3c2b1e;
  --user-digit: #7fb1e0;
  --error: #e07a7a;
  --error-soft: #422323;
  --easy: #6cbb92;
  --medium: #dcb35c;
  --hard: #dd8a5e;
  --expert: #b189ab;
  --shadow: 0 8px 24px rgba(0, 0, 0, 0.35);
  --overlay-scrim: rgba(0, 0, 0, 0.55);
}

* {
  box-sizing: border-box;
}

html,
body {
  height: 100%;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font-ui);
  -webkit-tap-highlight-color: transparent;
  transition: background 0.2s ease, color 0.2s ease;
}

button {
  font-family: inherit;
  color: inherit;
}

#app {
  max-width: 480px;
  min-height: 100vh;
  margin: 0 auto;
  padding: max(12px, env(safe-area-inset-top)) 8px
    max(24px, env(safe-area-inset-bottom));
  display: flex;
  flex-direction: column;
  position: relative;
}

/* ---------- top bar ---------- */

.top-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 4px 0 16px;
}

.wordmark {
  font-family: var(--font-display);
  font-weight: 600;
  font-size: 24px;
  margin: 0;
}

.top-bar-actions {
  display: flex;
  gap: 4px;
  min-width: 44px;
}

.icon-btn {
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  border: none;
  background: transparent;
  border-radius: 12px;
  color: var(--ink-soft);
  cursor: pointer;
  transition: background 0.15s ease, color 0.15s ease;
}

.icon-btn svg {
  width: 22px;
  height: 22px;
}

.icon-btn:hover {
  background: var(--accent-soft);
  color: var(--accent);
}

.icon-btn-sm {
  width: 32px;
  height: 32px;
  border-radius: 8px;
}

.icon-btn-sm svg {
  width: 18px;
  height: 18px;
}

/* ---------- stats card ---------- */

.stats-card {
  display: flex;
  align-items: stretch;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 14px 8px;
  box-shadow: var(--shadow);
}

.stat {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  padding: 0 8px;
  border: none;
  background: transparent;
  font-family: inherit;
  cursor: default;
}

.stat + .stat {
  border-left: 1px solid var(--border);
}

button.stat {
  cursor: pointer;
}

.stat-label {
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--ink-soft);
}

.stat-value {
  font-family: var(--font-display);
  font-weight: 600;
  font-size: 19px;
  color: var(--ink);
}

.stat-time-row {
  display: flex;
  align-items: center;
  gap: 6px;
}

.stat-mistakes[hidden],
.stat-time[hidden] {
  display: none;
}

/* ---------- board ---------- */

.board-wrap {
  position: relative;
  margin: 18px 0;
}

.board {
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  grid-template-rows: repeat(9, 1fr);
  aspect-ratio: 1;
  width: 100%;
  background: var(--surface);
  border: 2px solid var(--ink);
  border-radius: 12px;
  overflow: hidden;
}

:root.dark .board {
  border-color: var(--border);
}

.board.is-locked {
  pointer-events: none;
  opacity: 0.7;
}

.cell {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  border-right: 0.5px solid var(--border);
  border-bottom: 0.5px solid var(--border);
  cursor: pointer;
  background: var(--surface);
  user-select: none;
}

.cell:nth-child(9n) {
  border-right: none;
}

.cell:nth-last-child(-n + 9) {
  border-bottom: none;
}

.cell.box-edge-right {
  border-right: 1.5px solid var(--ink);
}

.cell.box-edge-bottom {
  border-bottom: 1.5px solid var(--ink);
}

:root.dark .cell.box-edge-right,
:root.dark .cell.box-edge-bottom {
  border-color: var(--border);
}

.cell.is-peer {
  background: var(--box-tint);
}

.cell.is-same-value {
  background: color-mix(in srgb, var(--ink-soft) 30%, var(--box-tint));
}

.cell.is-selected {
  background: color-mix(in srgb, var(--ink-soft) 30%, var(--box-tint));
}

.cell-value {
  font-family: var(--font-display);
  font-size: clamp(22px, 7.5vw, 32px);
  line-height: 1;
}

.cell.is-given .cell-value {
  font-weight: 600;
  color: var(--ink);
}

.cell.is-user .cell-value {
  font-weight: 600;
  color: var(--user-digit);
}

.cell.is-error .cell-value {
  color: var(--error) !important;
}

.cell-notes {
  position: absolute;
  inset: 3px;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
}

.cell-notes[hidden] {
  display: none;
}

.cell-note {
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: clamp(8px, 2.5vw, 12px);
  color: transparent;
  font-family: var(--font-ui);
  font-weight: 500;
}

.cell-note.is-active {
  color: var(--ink-soft);
}

.pause-overlay {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: color-mix(in srgb, var(--bg) 92%, transparent);
  backdrop-filter: blur(6px);
  border-radius: 12px;
}

.pause-overlay[hidden] {
  display: none;
}

.generating-label {
  font-family: var(--font-ui);
  font-weight: 600;
  color: var(--ink);
}

/* ---------- toolbar ---------- */

.toolbar {
  display: flex;
  align-items: stretch;
  gap: 8px;
  margin-bottom: 14px;
}

.segmented {
  flex: 1;
  display: flex;
  gap: 3px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 3px;
}

.segmented-btn {
  flex: 1;
  border: none;
  background: transparent;
  border-radius: 9px;
  padding: 10px 4px;
  font-family: inherit;
  font-size: 13px;
  font-weight: 600;
  color: var(--ink-soft);
  cursor: pointer;
  transition: background 0.15s ease, color 0.15s ease;
}

.segmented-btn.is-active {
  background: var(--ink);
  color: var(--surface);
}

.toolbar-undo-btn {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 0 16px;
  border: 1px solid var(--border);
  background: var(--surface);
  border-radius: 12px;
  color: var(--ink-soft);
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
}

.toolbar-undo-btn svg {
  width: 18px;
  height: 18px;
}

.toolbar-undo-btn:disabled {
  opacity: 0.4;
  cursor: default;
}

/* ---------- number pad ---------- */

.number-pad {
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: 4px;
}

.num-erase-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--ink-soft);
}

.num-erase-btn svg {
  width: 20px;
  height: 20px;
}

.num-erase-btn:disabled {
  opacity: 0.4;
  cursor: default;
}

.num-btn {
  aspect-ratio: 1;
  min-width: 0;
  min-height: 44px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--border);
  background: var(--surface);
  border-radius: 10px;
  cursor: pointer;
  position: relative;
}

.num-digit {
  font-family: var(--font-display);
  font-size: clamp(16px, 4.5vw, 20px);
  font-weight: 600;
  color: var(--ink);
}

.num-badge {
  font-size: 9px;
  color: var(--ink-soft);
  min-height: 11px;
}

.num-btn:hover:not(:disabled) {
  border-color: var(--accent);
}

.num-btn.is-depleted {
  opacity: 0.35;
  cursor: default;
}

/* ---------- buttons ---------- */

.btn {
  width: 100%;
  min-height: 48px;
  border-radius: 12px;
  border: none;
  font-family: inherit;
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  margin-top: 10px;
}

.btn-accent {
  background: var(--accent);
  color: #fff;
}

.btn-ghost {
  background: transparent;
  color: var(--ink-soft);
}

/* ---------- sheet / modal overlays ---------- */

.sheet-overlay,
.screen-overlay {
  position: fixed;
  inset: 0;
  z-index: 20;
  display: flex;
}

.sheet-overlay {
  align-items: flex-end;
  background: var(--overlay-scrim);
  backdrop-filter: blur(3px);
  animation: fade-in 0.15s ease;
}

.sheet-overlay[hidden],
.screen-overlay[hidden] {
  display: none;
}

.sheet {
  width: 100%;
  max-width: 480px;
  margin: 0 auto;
  background: var(--surface);
  border-radius: 20px 20px 0 0;
  padding: 10px 20px max(20px, env(safe-area-inset-bottom));
  box-shadow: var(--shadow);
  animation: slide-up 0.2s ease;
}

.sheet-center {
  border-radius: 20px;
  margin: auto;
  text-align: center;
  padding: 24px;
}

.sheet-handle {
  width: 36px;
  height: 4px;
  border-radius: 2px;
  background: var(--border);
  margin: 4px auto 14px;
}

.sheet-title {
  font-family: var(--font-display);
  font-size: 20px;
  font-weight: 600;
  margin: 0 0 6px;
}

.sheet-subtext {
  font-size: 13px;
  color: var(--ink-soft);
  margin: 0 0 16px;
}

.level-list {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.sheet-row {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  padding: 14px;
  border: 1px solid var(--border);
  background: var(--bg);
  border-radius: 12px;
  cursor: pointer;
  text-align: left;
  font-family: inherit;
}

.level-row-text {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.level-name {
  font-family: var(--font-display);
  font-weight: 600;
  font-size: 15px;
}

.level-easy {
  color: var(--easy);
}

.level-medium {
  color: var(--medium);
}

.level-hard {
  color: var(--hard);
}

.level-expert {
  color: var(--expert);
}

.level-count {
  font-size: 12px;
  color: var(--ink-soft);
}

.level-active-marker {
  font-size: 11px;
  font-weight: 600;
  color: var(--accent);
  background: var(--accent-soft);
  padding: 4px 8px;
  border-radius: 8px;
  white-space: nowrap;
}

.sheet-divider {
  height: 1px;
  background: var(--border);
  margin: 16px 0;
}

.sheet-row-action {
  flex-direction: column;
  align-items: flex-start;
  gap: 2px;
}

.sheet-row-hint {
  font-size: 12px;
  color: var(--ink-soft);
}

.sheet-cancel {
  margin-top: 12px;
}

.completion-stats {
  display: flex;
  justify-content: center;
  gap: 32px;
  margin: 12px 0 4px;
}

.completion-stat {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
}

/* ---------- settings screen ---------- */

.screen-overlay {
  flex-direction: column;
  background: var(--bg);
  overflow-y: auto;
  overflow-x: hidden;
  animation: fade-in 0.15s ease;
}

.screen-overlay > .top-bar {
  padding-left: 16px;
  padding-right: 16px;
}

.settings-body {
  max-width: 480px;
  width: 100%;
  margin: 0 auto;
  padding: 0 16px max(32px, env(safe-area-inset-bottom));
}

.settings-section {
  margin-bottom: 22px;
}

.settings-heading {
  font-family: var(--font-ui);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--ink-soft);
  margin: 0 0 8px 4px;
}

.settings-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 16px;
  overflow: hidden;
}

.settings-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 14px 16px;
}

.settings-row + .settings-row {
  border-top: 1px solid var(--border);
}

.settings-row-label {
  font-weight: 600;
  font-size: 14px;
}

.settings-row-desc {
  font-size: 12px;
  color: var(--ink-soft);
  margin-top: 2px;
}

.switch {
  flex-shrink: 0;
  width: 46px;
  height: 28px;
  border-radius: 14px;
  border: none;
  background: var(--border);
  position: relative;
  cursor: pointer;
  transition: background 0.15s ease;
}

.switch::after {
  content: "";
  position: absolute;
  top: 3px;
  left: 3px;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: #fff;
  transition: transform 0.15s ease;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.25);
}

.switch.is-on {
  background: var(--accent);
}

.switch.is-on::after {
  transform: translateX(18px);
}

.switch.is-locked {
  opacity: 0.6;
  cursor: default;
}

/* ---------- animations ---------- */

@keyframes fade-in {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}

@keyframes slide-up {
  from {
    transform: translateY(16px);
    opacity: 0;
  }
  to {
    transform: translateY(0);
    opacity: 1;
  }
}

@media (min-width: 540px) {
  #app {
    padding-top: 32px;
  }
}