body {
  --board-limit: min(420px, max(300px, calc(100svh - 330px)));
  --cell-font: clamp(1.15rem, 3vw, 1.75rem);
}

body[data-difficulty="easy"] {
  --board-limit: min(310px, calc(100vw - 40px));
  --cell-font: clamp(1.75rem, 4vw, 2.35rem);
}

body[data-difficulty="hard"] {
  --board-limit: min(512px, max(280px, calc(100svh - 380px)));
  --cell-font: clamp(0.92rem, 2.3vw, 1.42rem);
}

.board-column {
  display: flex;
  justify-content: center;
}

.board-card {
  width: 100%;
  padding: clamp(14px, 2vw, 22px);
  border: 1px solid var(--line);
  border-radius: 28px;
  background: color-mix(in srgb, var(--surface-raised) 92%, transparent);
  box-shadow: 0 24px 64px color-mix(in srgb, var(--ink) 12%, transparent);
  backdrop-filter: blur(10px);
}

.board-toolbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
  margin-bottom: 11px;
}

.board-toolbar h2 {
  margin: 2px 0 0;
  font-family: Georgia, "Times New Roman", serif;
  font-size: clamp(1.65rem, 2.7vw, 2.25rem);
  font-weight: 500;
  letter-spacing: -0.05em;
}

.difficulty-switch {
  display: inline-flex;
  padding: 3px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: var(--surface);
}

.difficulty-switch button {
  min-height: 40px;
  padding: 5px 11px;
  border: 0;
  border-radius: 10px;
  color: var(--muted);
  background: transparent;
  font-size: 0.68rem;
  font-weight: 850;
  line-height: 1.05;
}

.difficulty-switch button small {
  display: block;
  margin-top: 3px;
  font-size: 0.56rem;
  font-weight: 750;
}

.difficulty-switch button:hover {
  color: var(--blue);
}

.difficulty-switch button.is-active {
  color: var(--ink);
  background: var(--lime);
  box-shadow: 0 5px 12px color-mix(in srgb, var(--lime) 30%, transparent);
}

.puzzle-meta {
  display: grid;
  grid-template-columns: minmax(105px, 1.25fr) repeat(3, minmax(58px, 0.72fr));
  gap: 7px;
  margin-bottom: 11px;
}

.puzzle-meta > div,
.daily-button {
  min-height: 45px;
  display: grid;
  place-content: center;
  gap: 1px;
  padding: 5px 8px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--surface);
  text-align: center;
}

.puzzle-meta span,
.puzzle-meta div > span {
  color: var(--muted);
  font-size: 0.56rem;
  font-weight: 850;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.puzzle-meta strong,
.daily-button b {
  font-size: 0.82rem;
  font-variant-numeric: tabular-nums;
}

.daily-button {
  grid-template-columns: auto auto;
  align-items: center;
  border-color: color-mix(in srgb, var(--blue) 28%, var(--line));
  color: var(--blue);
  cursor: pointer;
}

.daily-button > span {
  color: inherit;
  font-size: 1rem;
}

.daily-button.is-active {
  border-color: var(--blue);
  color: var(--paper);
  background: var(--blue);
}

.board-wrap {
  width: 100%;
  min-height: var(--board-limit);
  display: grid;
  place-items: center;
}

.sudoku-board {
  width: min(100%, var(--board-limit));
  aspect-ratio: 1;
  display: grid;
  grid-template-columns: repeat(var(--grid-size), minmax(0, 1fr));
  grid-template-rows: repeat(var(--grid-size), minmax(0, 1fr));
  overflow: hidden;
  border: 3px solid var(--ink);
  border-radius: 16px;
  background: var(--ink);
  box-shadow: 0 14px 30px color-mix(in srgb, var(--ink) 18%, transparent);
}

.sudoku-cell {
  position: relative;
  min-width: 0;
  min-height: 0;
  display: grid;
  place-items: center;
  padding: 0;
  border: 0;
  border-right: 1px solid color-mix(in srgb, var(--ink) 19%, transparent);
  border-bottom: 1px solid color-mix(in srgb, var(--ink) 19%, transparent);
  color: var(--blue);
  background: var(--surface-raised);
  font-family: Georgia, "Times New Roman", serif;
  font-size: var(--cell-font);
  font-weight: 650;
  font-variant-numeric: tabular-nums;
  line-height: 1;
  isolation: isolate;
  transition: background 100ms ease, color 100ms ease, box-shadow 100ms ease;
}

.sudoku-cell.box-edge-right {
  border-right: 3px solid var(--ink);
}

.sudoku-cell.box-edge-bottom {
  border-bottom: 3px solid var(--ink);
}

.sudoku-cell.is-peer {
  background: color-mix(in srgb, var(--blue) 7%, var(--surface-raised));
}

.sudoku-cell.is-match {
  background: var(--color-primary-soft);
}

.sudoku-cell.is-given {
  color: var(--ink);
  background: color-mix(in srgb, var(--ink) 4%, var(--surface-raised));
  font-weight: 800;
}

.sudoku-cell.is-hint {
  color: var(--ink);
  background:
    radial-gradient(circle at 13% 13%, var(--lime) 0 4px, transparent 4.5px),
    var(--color-primary-soft);
}

.sudoku-cell.is-selected {
  z-index: 2;
  color: var(--ink);
  background: var(--color-secondary-soft);
  box-shadow: inset 0 0 0 3px var(--blue);
}

.sudoku-cell.is-error {
  color: color-mix(in srgb, var(--coral) 80%, var(--ink));
  background: var(--color-attention-soft);
  box-shadow: inset 0 0 0 2px var(--coral);
}

.sudoku-cell.is-error::after {
  content: "!";
  position: absolute;
  top: 3px;
  right: 4px;
  width: 13px;
  height: 13px;
  display: grid;
  place-items: center;
  border-radius: 50%;
  color: var(--ink);
  background: var(--coral);
  font-family: Inter, ui-sans-serif, system-ui, sans-serif;
  font-size: 0.54rem;
  font-weight: 950;
}

.cell-notes {
  width: 100%;
  height: 100%;
  display: grid;
  grid-template-columns: repeat(var(--box-columns), minmax(0, 1fr));
  place-items: center;
  padding: 4px;
}

.cell-notes i {
  color: var(--muted);
  font-family: Inter, ui-sans-serif, system-ui, sans-serif;
  font-size: clamp(0.42rem, 1.1vw, 0.63rem);
  font-style: normal;
  font-weight: 750;
  line-height: 1;
}

.number-pad {
  width: min(100%, var(--board-limit));
  display: grid;
  grid-template-columns: repeat(var(--digit-count), minmax(0, 1fr));
  gap: 6px;
  margin: 10px auto 0;
}

.number-pad button {
  min-width: 0;
  min-height: 42px;
  padding: 0;
  border: 1px solid var(--line);
  border-radius: 11px;
  color: var(--ink);
  background: var(--surface);
  font-family: Georgia, "Times New Roman", serif;
  font-size: 1rem;
  font-weight: 750;
  transition: transform 100ms ease, border-color 100ms ease, background 100ms ease;
}

.number-pad button:hover {
  transform: translateY(-1px);
  border-color: var(--blue);
  background: var(--color-secondary-soft);
}

.number-pad button.is-complete {
  color: var(--muted);
  background:
    linear-gradient(135deg, transparent 47%, var(--line) 48% 52%, transparent 53%),
    var(--surface);
}

.puzzle-actions {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 0.8fr)) minmax(86px, 1.1fr);
  gap: 7px;
  margin-top: 9px;
}

.puzzle-actions button {
  min-width: 0;
  min-height: 42px;
  padding: 6px 9px;
  border: 1px solid var(--line);
  border-radius: 11px;
  color: var(--ink);
  background: var(--surface);
  font-size: 0.7rem;
  font-weight: 850;
}

.puzzle-actions button span {
  margin-right: 4px;
  color: var(--blue);
}

.puzzle-actions .tool-button:hover,
.puzzle-actions .tool-button.is-active {
  border-color: var(--blue);
  background: var(--color-secondary-soft);
}

.puzzle-actions .check-button {
  border-color: transparent;
  background: var(--lime);
  box-shadow: 0 8px 18px color-mix(in srgb, var(--lime) 24%, transparent);
}

.puzzle-actions .check-button span {
  color: var(--ink);
}

.status-line {
  min-height: 18px;
  margin: 8px 0 -2px;
  color: var(--muted);
  font-size: 0.68rem;
  font-weight: 700;
  text-align: center;
}