:root {
  --page: #eef1ea;
  --surface: #fbfaf5;
  --surface-raised: #ffffff;
  --surface-muted: #e5eadf;
  --ink: #172421;
  --muted: #65736f;
  --line: rgba(23, 36, 33, 0.12);
  --line-strong: rgba(23, 36, 33, 0.42);
  --accent: #d94f3d;
  --accent-soft: rgba(217, 79, 61, 0.14);
  --accent-dark: #9c342a;
  --teal: #087d73;
  --teal-soft: rgba(8, 125, 115, 0.12);
  --blue: #245a9b;
  --blue-soft: rgba(36, 90, 155, 0.12);
  --error: #b3263d;
  --error-soft: rgba(179, 38, 61, 0.13);
  --shadow: 0 20px 50px rgba(23, 36, 33, 0.12);
  --radius: 8px;
  --font-display: "Avenir Next", "Trebuchet MS", sans-serif;
  --font-body: Georgia, "Times New Roman", serif;
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  min-height: 100%;
}

body {
  min-height: 100vh;
  color: var(--ink);
  font-family: var(--font-body);
  background:
    linear-gradient(90deg, rgba(23, 36, 33, 0.04) 1px, transparent 1px),
    linear-gradient(180deg, rgba(23, 36, 33, 0.035) 1px, transparent 1px),
    linear-gradient(135deg, #edf3ef 0%, #f5efe7 48%, #e8f0f2 100%);
  background-size: 28px 28px, 28px 28px, auto;
}

button {
  font: inherit;
}

.app-shell {
  width: min(1180px, calc(100vw - 32px));
  min-height: calc(100vh - 32px);
  margin: 16px auto;
  display: grid;
  grid-template-rows: auto auto 1fr;
  gap: 14px;
}

.topbar,
.command-bar,
.board-zone,
.panel-section,
.celebration-card {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: rgba(251, 250, 245, 0.88);
  box-shadow: var(--shadow);
  backdrop-filter: blur(14px);
}

.topbar {
  display: flex;
  align-items: stretch;
  justify-content: space-between;
  gap: 14px;
  padding: 14px;
}

.brand-lockup {
  display: grid;
  align-content: center;
  min-width: 180px;
  padding: 2px 4px;
}

.eyebrow {
  margin: 0 0 4px;
  color: var(--accent-dark);
  font-family: var(--font-display);
  font-size: 0.74rem;
  font-weight: 800;
  letter-spacing: 0;
  text-transform: uppercase;
}

h1,
h2 {
  margin: 0;
  font-family: var(--font-display);
  line-height: 1.02;
  letter-spacing: 0;
}

h1 {
  font-size: 4.2rem;
}

h2 {
  font-size: 1.25rem;
}

.stat-strip {
  display: grid;
  grid-template-columns: repeat(3, minmax(112px, 1fr));
  gap: 8px;
  min-width: min(100%, 430px);
}

.stat-pill {
  display: grid;
  align-content: center;
  min-height: 70px;
  padding: 12px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface-raised);
}

.stat-label,
.mini-label {
  display: block;
  margin-bottom: 5px;
  color: var(--muted);
  font-family: var(--font-display);
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0;
  text-transform: uppercase;
}

.stat-pill strong,
.mini-stats strong {
  font-family: var(--font-display);
  font-size: 1.15rem;
}

.command-bar {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 10px;
  padding: 10px;
}

.segmented-control,
.action-group,
.tool-row,
.board-footer,
.mini-stats {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.segmented-control {
  padding: 4px;
  border-radius: var(--radius);
  background: var(--surface-muted);
}

.segment,
.command-button,
.tool-button,
.number-button {
  min-height: 42px;
  border: 1px solid transparent;
  border-radius: var(--radius);
  cursor: pointer;
  transition:
    transform 140ms ease,
    box-shadow 140ms ease,
    background 140ms ease,
    border-color 140ms ease,
    color 140ms ease;
}

.segment {
  min-width: 88px;
  padding: 10px 14px;
  color: var(--muted);
  background: transparent;
  font-family: var(--font-display);
  font-weight: 750;
}

.segment.is-active {
  color: #fff;
  background: var(--ink);
  box-shadow: 0 10px 18px rgba(23, 36, 33, 0.18);
}

.command-button,
.tool-button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 10px 13px;
  color: var(--ink);
  background: var(--surface-raised);
  border-color: var(--line);
  font-family: var(--font-display);
  font-weight: 750;
}

.command-button:disabled {
  color: rgba(23, 36, 33, 0.35);
  cursor: not-allowed;
  background: rgba(255, 255, 255, 0.48);
}

.button-icon {
  display: grid;
  place-items: center;
  width: 20px;
  height: 20px;
  border-radius: 6px;
  color: #fff;
  background: var(--teal);
  font-family: var(--font-display);
  font-size: 0.9rem;
  line-height: 1;
}

.playfield {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 330px;
  gap: 14px;
  align-items: start;
}

.board-zone {
  padding: 16px;
}

.board-frame {
  padding: 10px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background:
    linear-gradient(135deg, rgba(8, 125, 115, 0.1), transparent 34%),
    linear-gradient(315deg, rgba(217, 79, 61, 0.11), transparent 36%),
    var(--surface-raised);
}

.sudoku-board {
  display: grid;
  grid-template-columns: repeat(9, minmax(0, 1fr));
  width: min(100%, calc(100vh - 204px), 720px);
  min-width: 0;
  margin: 0 auto;
  border: 2px solid var(--line-strong);
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--surface-raised);
}

.sudoku-cell {
  position: relative;
  aspect-ratio: 1;
  display: grid;
  place-items: center;
  min-width: 0;
  padding: 0;
  color: var(--ink);
  background: rgba(255, 255, 255, 0.9);
  border: 1px solid var(--line);
  font-family: var(--font-display);
  font-size: 2.1rem;
  font-weight: 800;
}

.sudoku-cell[data-band-edge="bottom"] {
  border-bottom-width: 2px;
  border-bottom-color: var(--line-strong);
}

.sudoku-cell[data-stack-edge="right"] {
  border-right-width: 2px;
  border-right-color: var(--line-strong);
}

.sudoku-cell.is-fixed {
  color: var(--blue);
  background: var(--blue-soft);
}

.sudoku-cell.is-related {
  background: rgba(8, 125, 115, 0.08);
}

.sudoku-cell.is-selected {
  z-index: 1;
  background: rgba(217, 79, 61, 0.12);
  box-shadow: inset 0 0 0 3px var(--accent);
}

.sudoku-cell.is-match {
  background: rgba(8, 125, 115, 0.16);
}

.sudoku-cell.is-error {
  color: var(--error);
  background: var(--error-soft);
  box-shadow: inset 0 0 0 2px var(--error);
}

.sudoku-cell:focus-visible,
.number-button:focus-visible,
.segment:focus-visible,
.command-button:focus-visible,
.tool-button:focus-visible,
.popover-number:focus-visible,
.popover-tool:focus-visible {
  outline: 3px solid rgba(8, 125, 115, 0.34);
  outline-offset: 2px;
}

.segment:hover,
.command-button:hover:not(:disabled),
.tool-button:hover,
.number-button:hover,
.sudoku-cell:hover {
  transform: translateY(-1px);
}

.cell-value {
  pointer-events: none;
}

.note-grid {
  width: 100%;
  height: 100%;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  padding: 5px;
  gap: 1px;
  color: var(--teal);
  font-family: var(--font-display);
  font-size: 0.72rem;
  font-weight: 700;
  pointer-events: none;
}

.note-grid span {
  display: grid;
  place-items: center;
}

.board-footer {
  margin-top: 10px;
}

.legend-chip {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  padding: 7px 9px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  color: var(--muted);
  background: var(--surface-raised);
  font-size: 0.9rem;
}

.swatch {
  width: 11px;
  height: 11px;
  border-radius: 3px;
}

.swatch-fixed {
  background: var(--blue);
}

.swatch-note {
  background: var(--teal);
}

.swatch-error {
  background: var(--error);
}

.side-panel {
  display: grid;
  gap: 12px;
}

.panel-section {
  padding: 12px;
  box-shadow: none;
  background: var(--surface-raised);
}

.keypad {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 8px;
}

.number-button {
  min-height: 74px;
  color: var(--ink);
  background: linear-gradient(180deg, #fff, #eef4ee);
  border-color: var(--line);
  font-family: var(--font-display);
  font-size: 1.55rem;
  font-weight: 850;
}

.number-button.is-complete {
  color: rgba(23, 36, 33, 0.36);
  background: rgba(229, 234, 223, 0.58);
}

.tool-row {
  margin-top: 8px;
}

.tool-button {
  flex: 1 1 0;
}

.tool-button.is-active {
  color: #fff;
  background: var(--teal);
  border-color: var(--teal);
}

.tool-button.danger {
  color: var(--error);
}

.progress-header {
  margin-bottom: 10px;
}

.progress-meter {
  height: 10px;
  overflow: hidden;
  border-radius: 999px;
  background: var(--surface-muted);
}

.progress-meter span {
  display: block;
  width: 0%;
  height: 100%;
  border-radius: inherit;
  background: linear-gradient(90deg, var(--teal), var(--accent));
  transition: width 180ms ease;
}

.status-message {
  min-height: 48px;
  margin: 12px 0 0;
  color: var(--muted);
  line-height: 1.45;
}

.mini-stats {
  justify-content: space-between;
  margin-top: 10px;
}

.mini-stats div {
  min-width: 70px;
}

.celebration {
  position: fixed;
  inset: 0;
  z-index: 3;
  display: grid;
  place-items: center;
  padding: 24px;
  background: rgba(23, 36, 33, 0.28);
  backdrop-filter: blur(6px);
}

.celebration.hidden {
  display: none;
}

.cell-popover {
  position: fixed;
  z-index: 4;
  width: min(236px, calc(100vw - 24px));
  padding: 8px;
  border: 1px solid rgba(23, 36, 33, 0.16);
  border-radius: var(--radius);
  background: rgba(255, 255, 255, 0.96);
  box-shadow: 0 18px 44px rgba(23, 36, 33, 0.2);
  backdrop-filter: blur(14px);
}

.cell-popover.hidden {
  display: none;
}

.cell-popover::before {
  content: "";
  position: absolute;
  top: -7px;
  left: var(--popover-arrow-left, 24px);
  width: 12px;
  height: 12px;
  border-top: 1px solid rgba(23, 36, 33, 0.16);
  border-left: 1px solid rgba(23, 36, 33, 0.16);
  background: rgba(255, 255, 255, 0.96);
  transform: rotate(45deg);
}

.popover-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 6px;
}

.popover-number,
.popover-tool {
  min-height: 42px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  color: var(--ink);
  background: linear-gradient(180deg, #fff, #eef4ee);
  cursor: pointer;
  font-family: var(--font-display);
  font-weight: 850;
}

.popover-number {
  font-size: 1.15rem;
}

.popover-actions {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 6px;
  margin-top: 6px;
}

.popover-tool {
  color: var(--muted);
  font-size: 0.9rem;
}

.celebration-card {
  width: min(420px, 100%);
  padding: 28px;
  text-align: center;
  background: var(--surface-raised);
}

.celebration-card p {
  color: var(--muted);
  line-height: 1.55;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  border: 0;
}

@media (max-width: 980px) {
  .app-shell {
    width: min(760px, calc(100vw - 24px));
  }

  .topbar,
  .playfield {
    grid-template-columns: 1fr;
  }

  .topbar {
    display: grid;
  }

  .playfield {
    display: grid;
  }

  .sudoku-board {
    width: min(100%, 720px);
  }
}

@media (max-width: 640px) {
  .app-shell {
    width: calc(100vw - 16px);
    margin: 8px auto;
    gap: 8px;
  }

  .topbar,
  .command-bar,
  .board-zone,
  .side-panel {
    padding: 8px;
  }

  h1 {
    font-size: 2rem;
  }

  .stat-strip {
    grid-template-columns: repeat(3, minmax(0, 1fr));
    min-width: 0;
  }

  .stat-pill {
    min-height: 58px;
    padding: 8px;
  }

  .stat-pill strong,
  .mini-stats strong {
    font-size: 1rem;
  }

  .command-bar,
  .action-group,
  .segmented-control {
    width: 100%;
  }

  .segment {
    flex: 1 1 0;
    min-width: 0;
  }

  .command-button {
    flex: 1 1 calc(50% - 4px);
  }

  .board-frame {
    padding: 6px;
  }

  .sudoku-cell {
    font-size: 1.18rem;
  }

  .note-grid {
    padding: 2px;
    font-size: 0.5rem;
  }

  .number-button {
    min-height: 54px;
    font-size: 1.25rem;
  }
}