:root {
  color-scheme: light;
  --ink: #202124;
  --muted: #65707a;
  --paper: #f3f0e9;
  --panel: #fffdfa;
  --line: #d9d3c8;
  --accent: #2f80a8;
  --accent-dark: #1f5d7b;
  --warn: #d95043;
  --ok: #4f8d5f;
  --given: #ede7da;
  --shadow: 0 22px 50px rgba(44, 36, 24, 0.15);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  background:
    linear-gradient(135deg, rgba(47, 128, 168, 0.16), transparent 34%),
    linear-gradient(225deg, rgba(232, 184, 79, 0.18), transparent 44%),
    var(--paper);
  color: var(--ink);
}

button,
select {
  font: inherit;
}

button {
  border: 0;
  cursor: pointer;
}

.app-shell {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 320px;
  gap: 14px;
  min-height: 100vh;
  padding: 14px;
}

.game-panel,
.lesson-panel {
  background: rgba(255, 253, 250, 0.9);
  border: 1px solid rgba(217, 211, 200, 0.92);
  border-radius: 8px;
  box-shadow: var(--shadow);
}

.game-panel {
  display: grid;
  grid-template-rows: auto auto minmax(0, 1fr) auto;
  min-width: 0;
}

.topbar {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 14px;
  padding: 20px 22px 12px;
}

.eyebrow {
  margin: 0 0 6px;
  color: var(--muted);
  font-size: 0.76rem;
  font-weight: 900;
  letter-spacing: 0;
  text-transform: uppercase;
}

h1,
h2 {
  margin: 0;
  letter-spacing: 0;
}

h1 {
  font-size: clamp(2rem, 4vw, 3.8rem);
  line-height: 0.96;
}

h2 {
  font-size: 1.4rem;
}

.controls {
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-end;
  gap: 8px;
}

.select-control,
.controls button,
.number-pad button {
  min-height: 42px;
  border-radius: 8px;
  background: #eee8dc;
  color: var(--ink);
  font-weight: 900;
}

.select-control {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 0 10px 0 12px;
  color: var(--muted);
  font-size: 0.86rem;
}

.select-control select {
  min-width: 112px;
  border: 0;
  border-radius: 6px;
  padding: 5px 7px;
  background: #fffdfa;
  color: var(--ink);
  font-weight: 900;
}

.controls button {
  padding: 0 14px;
}

.controls button:hover,
.number-pad button:hover {
  transform: translateY(-1px);
}

#checkPuzzle {
  background: var(--ink);
  color: #fffdfa;
}

.status-strip {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
  margin: 0 22px 12px;
  padding: 10px 12px;
  border-radius: 8px;
  background: #eee8dc;
  color: var(--muted);
  font-weight: 850;
}

.status-strip strong {
  flex: 0 0 auto;
  color: var(--ink);
  font-variant-numeric: tabular-nums;
  position: relative;
}

.status-strip.ok {
  background: rgba(79, 141, 95, 0.18);
  color: #2f6139;
}

.status-strip.warn {
  background: rgba(217, 80, 67, 0.14);
  color: #873329;
}

.board-wrap {
  display: grid;
  place-items: center;
  min-height: 0;
  padding: 10px 22px 18px;
}

.sudoku-board {
  display: grid;
  grid-template-columns: repeat(var(--grid-size, 4), 1fr);
  width: min(520px, 100%);
  aspect-ratio: 1;
  border: 5px solid var(--ink);
  border-radius: 8px;
  overflow: hidden;
  background: var(--ink);
  box-shadow: 0 18px 38px rgba(35, 28, 19, 0.18);
}

.cell {
  display: grid;
  place-items: center;
  min-width: 0;
  min-height: 0;
  border: 1px solid #c9c1b3;
  background: #fffdfa;
  color: var(--accent-dark);
  font-size: clamp(1.05rem, 3.8vw, 2.6rem);
  font-weight: 950;
  font-variant-numeric: tabular-nums;
  position: relative;
}

.cell.box-right::after,
.cell.box-bottom::before {
  content: "";
  position: absolute;
  z-index: 2;
  pointer-events: none;
  background: var(--ink);
}

.cell.box-right::after {
  top: 0;
  right: -2px;
  bottom: 0;
  width: 5px;
}

.cell.box-bottom::before {
  left: 0;
  right: 0;
  bottom: -2px;
  height: 5px;
}

.cell.shaded-box {
  background: #eeeeea;
}

.cell.given {
  background: var(--given);
  color: var(--ink);
}

.cell.given.shaded-box {
  background: #ded9cf;
}

.cell.selected {
  background: rgba(47, 128, 168, 0.1);
  outline: 3px solid var(--accent);
  outline-offset: -3px;
}

.cell.peer {
  box-shadow: inset 0 0 0 2px rgba(47, 128, 168, 0.08);
}

.cell.conflict {
  background: rgba(217, 80, 67, 0.16);
  color: #8f3028;
}

.cell-notes {
  display: grid;
  grid-template-columns: repeat(var(--note-columns, 3), 1fr);
  width: 88%;
  height: 88%;
  align-items: center;
  justify-items: center;
  color: #5f6971;
  font-size: clamp(0.48rem, 1.25vw, 0.92rem);
  font-weight: 800;
  line-height: 1;
}

.sudoku-board[data-size="4"] .cell-notes {
  font-size: clamp(0.7rem, 2vw, 1.2rem);
}

.sudoku-board[data-size="6"] .cell-notes {
  font-size: clamp(0.56rem, 1.45vw, 1rem);
}

.notes-popover {
  position: fixed;
  z-index: 50;
  padding: 10px;
  border: 1px solid rgba(32, 33, 36, 0.22);
  border-radius: 8px;
  background: #fffdfa;
  box-shadow: 0 18px 40px rgba(35, 28, 19, 0.24);
}

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

.notes-popover-grid button,
.notes-done {
  min-height: 42px;
  border: 0;
  border-radius: 8px;
  background: #eee8dc;
  color: var(--ink);
  font-weight: 900;
}

.notes-popover-grid button.active {
  background: var(--accent);
  color: #fffdfa;
}

.notes-done {
  width: 100%;
  margin-top: 8px;
  background: var(--ink);
  color: #fffdfa;
}


.number-pad {
  display: grid;
  grid-template-columns: repeat(var(--pad-columns, 5), minmax(0, 1fr));
  gap: 8px;
  padding: 0 22px 22px;
}

.number-pad button {
  padding: 0 10px;
}

.lesson-panel {
  padding: 20px 22px;
  line-height: 1.5;
}

.lesson-panel p {
  margin: 0 0 14px;
}

@media (max-width: 980px) {
  .app-shell {
    grid-template-columns: 1fr;
  }

  .game-panel {
    grid-template-rows: auto auto auto auto;
  }
}

@media (max-width: 620px) {
  .app-shell {
    gap: 10px;
    padding: 8px;
  }

  .topbar {
    display: grid;
    grid-template-columns: 1fr;
    gap: 12px;
    padding: 18px 14px 12px;
  }

  h1 {
    font-size: 2.2rem;
  }

  .controls {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 7px;
  }

  .select-control,
  .controls button,
  .number-pad button {
    min-height: 40px;
  }

  .select-control {
    justify-content: space-between;
  }

  .select-control select {
    min-width: 94px;
  }

  .status-strip {
    margin: 0 14px 12px;
  }

  .board-wrap {
    padding: 8px 14px 18px;
  }

  .sudoku-board {
    width: min(100%, 430px);
  }

  .cell {
    font-size: clamp(0.95rem, 7vw, 2.4rem);
  }

  .cell-notes {
    font-size: clamp(0.44rem, 2.6vw, 0.9rem);
  }

  .sudoku-board[data-size="4"] .cell-notes {
    font-size: clamp(0.7rem, 4vw, 1.2rem);
  }

  .number-pad[data-size="6"] {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

  .number-pad[data-size="9"] {
    grid-template-columns: repeat(5, minmax(0, 1fr));
  }

  .number-pad {
    padding: 0 14px 18px;
  }

  .lesson-panel {
    padding: 20px;
  }
}


.print-sheet {
  display: none;
}

@media print {
  @page {
    size: letter portrait;
    margin: 0.35in;
  }

  * {
    box-shadow: none !important;
  }

  body {
    min-height: auto;
    background: #fff;
    color: #111;
  }

  .app-shell {
    display: none;
  }

  .print-sheet {
    display: grid;
    grid-template-rows: auto 1fr;
    gap: 0.18in;
    width: 7.0in;
    max-width: 100%;
    height: 10.1in;
    margin: 0 auto;
    overflow: visible;
    page-break-after: avoid;
    page-break-before: avoid;
  }

  .print-header {
    display: flex;
    align-items: end;
    justify-content: space-between;
    gap: 0.2in;
    border-bottom: 2px solid #111;
    padding-bottom: 0.08in;
  }

  .print-header p {
    margin: 0 0 0.03in;
    color: #555;
    font-size: 9pt;
    font-weight: 900;
    text-transform: uppercase;
  }

  .print-header h1 {
    margin: 0;
    color: #111;
    font-size: 20pt;
    line-height: 1;
  }

  .print-meta {
    display: grid;
    grid-template-columns: 1.35in 1.05in;
    gap: 0.16in;
    color: #555;
    font-size: 9pt;
    font-weight: 800;
  }

  .print-meta span::after {
    content: "";
    display: block;
    margin-top: 0.12in;
    border-bottom: 1px solid #111;
  }

  .print-puzzles {
    display: grid;
    grid-template-columns: repeat(2, 3.18in);
    grid-template-rows: repeat(2, minmax(0, 1fr));
    justify-content: center;
    align-content: start;
    gap: 0.46in 0.28in;
    min-width: 0;
    padding-top: 0.1in;
    min-height: 0;
  }

  .print-puzzle {
    display: grid;
    grid-template-rows: auto minmax(0, 1fr);
    justify-items: center;
    min-width: 0;
    min-height: 0;
    overflow: visible;
    page-break-inside: avoid;
  }

  .print-puzzle h2 {
    justify-self: start;
    margin: 0 0 0.05in;
    color: #333;
    font-size: 11pt;
    font-weight: 900;
  }

  .print-board {
    display: grid;
    grid-template-columns: repeat(var(--grid-size), 1fr);
    box-sizing: border-box;
    width: 3.0in;
    aspect-ratio: 1;
    border: 3px solid #111;
    background: #111;
    overflow: visible;
  }

  .print-cell {
    display: grid;
    place-items: center;
    min-width: 0;
    border: 0.75px solid #555;
    background: #fff;
    color: #111;
    font-family: Arial, Helvetica, sans-serif;
    font-size: 17pt;
    line-height: 1;
    -webkit-print-color-adjust: exact;
    print-color-adjust: exact;
  }

  .print-cell.shaded-box {
    background: #dddddd !important;
    -webkit-print-color-adjust: exact;
    print-color-adjust: exact;
  }

  .print-cell.box-right {
    border-right: 2.5px solid #111;
  }

  .print-cell.box-bottom {
    border-bottom: 2.5px solid #111;
  }

  .print-sheet[data-size="4"] .print-board {
    width: 2.9in;
  }

  .print-sheet[data-size="4"] .print-cell {
    font-size: 24pt;
  }

  .print-sheet[data-size="6"] .print-board {
    width: 2.95in;
  }

  .print-sheet[data-size="6"] .print-cell {
    font-size: 19pt;
  }

  .print-sheet[data-size="9"] .print-board {
    width: 3.0in;
  }

  .print-sheet[data-size="9"] .print-cell {
    font-size: 14pt;
  }
}