:root {
  --paper: #f1eadc;
  --paper-deep: #e2d6c2;
  --paper-light: #faf6ed;
  --ink: #24211d;
  --ink-soft: #625b51;
  --line: #9c9283;
  --line-light: rgba(36, 33, 29, 0.18);
  --accent: #a43b2d;
  --accent-dark: #79271f;
  --accent-wash: rgba(164, 59, 45, 0.12);
  --focus: #236a6e;
  --success: #376b4b;
  --success-wash: rgba(55, 107, 75, 0.12);
  --warning: #926319;
  --warning-wash: rgba(146, 99, 25, 0.12);
  --display-font: "I.Ming", "Noto Serif TC", "Yu Mincho", "PMingLiU", serif;
  --body-font: "Aptos", "Noto Sans TC", "Microsoft JhengHei", sans-serif;
  --shadow-paper: 0 1.2rem 3rem rgba(49, 39, 24, 0.14);
  --radius-small: 0.25rem;
}

* {
  box-sizing: border-box;
}

html {
  color-scheme: light;
  scroll-behavior: smooth;
}

body {
  min-width: 20rem;
  min-height: 100vh;
  margin: 0;
  color: var(--ink);
  font-family: var(--body-font);
  background:
    radial-gradient(circle at 8% 8%, rgba(255, 255, 255, 0.65), transparent 28rem),
    repeating-linear-gradient(
      8deg,
      rgba(73, 57, 35, 0.018) 0,
      rgba(73, 57, 35, 0.018) 1px,
      transparent 1px,
      transparent 5px
    ),
    var(--paper-deep);
}

button,
input {
  font: inherit;
}

button {
  color: inherit;
}

.skip-link {
  position: fixed;
  z-index: 20;
  top: -10rem;
  left: 0.75rem;
  padding: 0.7rem 1rem;
  color: var(--paper-light);
  background: var(--ink);
  transition: top 160ms ease;
}

.skip-link:focus {
  top: 0.75rem;
}

.page-shell {
  width: min(92rem, calc(100% - 2rem));
  min-height: calc(100vh - 2rem);
  margin: 1rem auto;
  padding: clamp(1.2rem, 3vw, 3.4rem);
  overflow: hidden;
  background:
    linear-gradient(90deg, transparent 2.45rem, rgba(164, 59, 45, 0.13) 2.5rem, transparent 2.55rem),
    var(--paper-light);
  border: 1px solid rgba(36, 33, 29, 0.25);
  box-shadow: var(--shadow-paper);
}

.masthead {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: clamp(1rem, 3vw, 2.5rem);
  align-items: center;
  padding-bottom: clamp(1.5rem, 3vw, 2.5rem);
  border-bottom: 3px double var(--ink);
  animation: reveal 620ms cubic-bezier(0.22, 1, 0.36, 1) both;
}

.masthead__marker {
  display: grid;
  width: clamp(5rem, 10vw, 7.4rem);
  aspect-ratio: 1;
  place-items: center;
  color: var(--paper-light);
  background: var(--accent);
  border-radius: 50%;
  box-shadow: inset 0 0 0 0.28rem var(--accent), inset 0 0 0 0.36rem var(--paper-light);
  transform: rotate(-6deg);
}

.masthead__marker span {
  margin-top: 0.45rem;
  font-family: var(--display-font);
  font-size: clamp(2.3rem, 5vw, 3.8rem);
  line-height: 0.8;
}

.masthead__marker small {
  margin-top: -1.35rem;
  font-size: 0.62rem;
  font-weight: 800;
  letter-spacing: 0.18em;
  text-transform: uppercase;
}

.eyebrow,
.section-kicker {
  margin: 0 0 0.45rem;
  color: var(--accent);
  font-size: 0.72rem;
  font-weight: 800;
  letter-spacing: 0.18em;
  text-transform: uppercase;
}

h1,
h2,
p {
  margin-top: 0;
}

h1 {
  margin-bottom: 0.5rem;
  font-family: var(--display-font);
  font-size: clamp(3rem, 7.8vw, 7.4rem);
  font-weight: 700;
  letter-spacing: -0.065em;
  line-height: 0.92;
}

.deck {
  max-width: 38rem;
  margin-bottom: 0;
  color: var(--ink-soft);
  font-family: var(--display-font);
  font-size: clamp(1rem, 1.5vw, 1.25rem);
  line-height: 1.65;
}

.masthead__rule {
  grid-column: 1 / -1;
  display: flex;
  justify-content: space-between;
  margin-top: 0.15rem;
  padding-top: 0.55rem;
  border-top: 1px solid var(--line);
  color: var(--ink-soft);
  font-size: 0.62rem;
  font-weight: 800;
  letter-spacing: 0.15em;
}

.workspace {
  display: grid;
  grid-template-columns: minmax(31rem, 1.35fr) minmax(18rem, 0.65fr);
  gap: clamp(2.5rem, 6vw, 6.5rem);
  align-items: start;
  padding: clamp(2rem, 5vw, 5rem) 0;
}

.puzzle-sheet {
  animation: rise-in 650ms 100ms cubic-bezier(0.22, 1, 0.36, 1) both;
}

.section-heading {
  display: flex;
  gap: 1rem;
  align-items: end;
  justify-content: space-between;
  margin-bottom: 1.1rem;
}

.section-heading h2 {
  margin-bottom: 0;
  font-family: var(--display-font);
  font-size: clamp(2rem, 4vw, 3.5rem);
  line-height: 1;
}

.progress-label {
  margin-bottom: 0.2rem;
  color: var(--ink-soft);
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.08em;
}

.board-stage {
  position: relative;
  padding: clamp(0.75rem, 2vw, 1.3rem);
  background: var(--paper);
  border: 1px solid var(--line);
  box-shadow: 0.7rem 0.8rem 0 var(--accent-wash);
}

.board-stage__index {
  position: absolute;
  z-index: 2;
  top: -1rem;
  right: -0.65rem;
  padding: 0.42rem 0.65rem;
  color: var(--paper-light);
  background: var(--ink);
  font-size: 0.62rem;
  font-weight: 800;
  letter-spacing: 0.14em;
  transform: rotate(2deg);
}

.sudoku-board {
  display: grid;
  width: 100%;
  overflow: hidden;
  grid-template-columns: repeat(9, minmax(0, 1fr));
  background: var(--ink);
  border: 3px solid var(--ink);
  outline: none;
}

.cell {
  position: relative;
  min-width: 0;
  min-height: 0;
  aspect-ratio: 1;
  background: var(--paper-light);
  border-right: 1px solid var(--line-light);
  border-bottom: 1px solid var(--line-light);
  transition: background-color 130ms ease;
}

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

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

.cell.last-column {
  border-right: 0;
}

.cell.last-row {
  border-bottom: 0;
}

.cell.is-related {
  background: #eee3d1;
}

.cell.is-peer-value {
  background: #e7d7be;
}

.cell.is-conflict {
  z-index: 1;
  background: #f5dcd5;
  box-shadow: inset 0 0 0 3px var(--accent);
}

.cell.is-conflict::after {
  content: "!";
  position: absolute;
  z-index: 3;
  top: 0.14rem;
  right: 0.18rem;
  display: grid;
  width: 1rem;
  height: 1rem;
  place-items: center;
  color: var(--paper-light);
  background: var(--accent);
  border-radius: 50%;
  font-size: 0.65rem;
  font-weight: 900;
  line-height: 1;
  pointer-events: none;
}

.cell input {
  position: relative;
  z-index: 2;
  min-width: 0;
  width: 100%;
  height: 100%;
  padding: 0;
  color: var(--ink);
  caret-color: var(--accent);
  background: transparent;
  border: 0;
  border-radius: 0;
  outline: 0;
  font-family: var(--display-font);
  font-size: clamp(1.35rem, 4vw, 3rem);
  font-weight: 700;
  line-height: 1;
  text-align: center;
}

.cell input:focus-visible {
  box-shadow: inset 0 0 0 4px var(--focus);
}

.cell.is-solved input {
  color: var(--accent);
  font-style: italic;
  font-weight: 600;
}

.cell input[readonly] {
  cursor: default;
}

.legend {
  display: flex;
  flex-wrap: wrap;
  gap: 0.7rem 1.25rem;
  margin: 1.15rem 0 0;
  color: var(--ink-soft);
  font-size: 0.72rem;
  font-weight: 700;
}

.legend span {
  display: inline-flex;
  gap: 0.45rem;
  align-items: center;
}

.legend__swatch {
  display: inline-block;
  width: 0.8rem;
  height: 0.8rem;
  border: 1px solid var(--line);
}

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

.legend__swatch--answer {
  background: var(--accent);
}

.legend__swatch--conflict {
  background: #f5dcd5;
  box-shadow: inset 0 0 0 2px var(--accent);
}

.actions {
  display: grid;
  grid-template-columns: minmax(11rem, 1.4fr) repeat(3, minmax(7rem, 1fr));
  gap: 0.65rem;
  margin-top: 1.4rem;
}

.button {
  min-height: 3rem;
  padding: 0.75rem 1rem;
  color: var(--ink);
  background: transparent;
  border: 1px solid var(--ink);
  border-radius: var(--radius-small);
  font-size: 0.82rem;
  font-weight: 800;
  letter-spacing: 0.03em;
  cursor: pointer;
  transition:
    color 150ms ease,
    background-color 150ms ease,
    transform 150ms ease;
}

.button:hover:not(:disabled) {
  color: var(--paper-light);
  background: var(--ink);
  transform: translateY(-2px);
}

.button:focus-visible {
  outline: 3px solid var(--focus);
  outline-offset: 3px;
}

.button--primary {
  display: flex;
  gap: 1rem;
  align-items: center;
  justify-content: space-between;
  color: var(--paper-light);
  background: var(--accent);
  border-color: var(--accent);
  font-size: 0.9rem;
}

.button--primary:hover:not(:disabled) {
  background: var(--accent-dark);
}

.button--quiet {
  color: var(--ink-soft);
  border-color: var(--line);
}

.button:disabled {
  opacity: 0.42;
  cursor: not-allowed;
}

.editorial-notes {
  display: grid;
  gap: 2rem;
  padding-top: 1.5rem;
  animation: rise-in 650ms 180ms cubic-bezier(0.22, 1, 0.36, 1) both;
}

.status-card {
  position: relative;
  padding: 1.35rem 1.4rem 1.5rem;
  background: var(--ink);
  border-left: 0.42rem solid var(--ink-soft);
  color: var(--paper-light);
  outline: none;
}

.status-card:focus-visible {
  box-shadow: 0 0 0 4px var(--focus);
}

.status-card--success {
  background: #274938;
  border-left-color: #7fbd91;
}

.status-card--error {
  background: var(--accent-dark);
  border-left-color: #e8a093;
}

.status-card--warning {
  background: #6c4b19;
  border-left-color: #e0b768;
}

.status-card--info {
  background: #355d60;
  border-left-color: #83bfc1;
}

.status-card__topline {
  display: flex;
  gap: 0.45rem;
  align-items: center;
  margin-bottom: 1.15rem;
  font-size: 0.62rem;
  font-weight: 900;
  letter-spacing: 0.17em;
}

.status-card__dot {
  width: 0.52rem;
  height: 0.52rem;
  background: currentColor;
  border-radius: 50%;
  box-shadow: 0 0 0 0.25rem rgba(255, 255, 255, 0.12);
}

.status-card h2 {
  margin-bottom: 0.45rem;
  font-family: var(--display-font);
  font-size: clamp(1.65rem, 3vw, 2.45rem);
}

.status-card p {
  margin-bottom: 0;
  color: rgba(250, 246, 237, 0.84);
  font-size: 0.9rem;
  line-height: 1.75;
}

.note-block {
  display: grid;
  grid-template-columns: 2.5rem minmax(0, 1fr);
  gap: 1rem;
  padding-top: 1.1rem;
  border-top: 1px solid var(--line);
}

.note-number {
  margin: 0;
  color: var(--accent);
  font-family: var(--display-font);
  font-size: 1.8rem;
  font-weight: 800;
  line-height: 1;
}

.note-block h2 {
  margin-bottom: 0.8rem;
  font-family: var(--display-font);
  font-size: 1.25rem;
}

.note-block ol {
  margin: 0;
  padding-left: 1.2rem;
  color: var(--ink-soft);
  font-size: 0.88rem;
  line-height: 1.8;
}

.key-list {
  display: grid;
  gap: 0.6rem;
  margin: 0;
}

.key-list div {
  display: grid;
  grid-template-columns: 6.3rem 1fr;
  gap: 0.5rem;
  align-items: center;
}

.key-list dt,
.key-list dd {
  margin: 0;
}

.key-list dd {
  color: var(--ink-soft);
  font-size: 0.8rem;
}

kbd {
  display: inline-block;
  min-width: 1.7rem;
  padding: 0.24rem 0.4rem;
  color: var(--ink);
  background: var(--paper);
  border: 1px solid var(--line);
  border-bottom-width: 2px;
  border-radius: 0.2rem;
  font-family: var(--body-font);
  font-size: 0.68rem;
  font-weight: 800;
  text-align: center;
}

blockquote {
  margin: 0;
  padding: 1.2rem 0 0 2.2rem;
  color: var(--ink-soft);
  border-top: 3px double var(--ink);
  font-family: var(--display-font);
  font-size: clamp(1.1rem, 2vw, 1.4rem);
  font-style: italic;
  line-height: 1.8;
}

footer {
  display: flex;
  gap: 1rem;
  justify-content: space-between;
  padding-top: 1rem;
  color: var(--ink-soft);
  border-top: 3px double var(--ink);
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.06em;
}

footer p {
  margin-bottom: 0;
}

.noscript-message {
  position: fixed;
  z-index: 30;
  right: 1rem;
  bottom: 1rem;
  left: 1rem;
  margin: 0;
  padding: 1rem;
  color: white;
  background: var(--accent-dark);
  text-align: center;
}

@keyframes reveal {
  from {
    opacity: 0;
    clip-path: inset(0 100% 0 0);
  }
  to {
    opacity: 1;
    clip-path: inset(0);
  }
}

@keyframes rise-in {
  from {
    opacity: 0;
    transform: translateY(1.4rem);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@media (max-width: 62rem) {
  .workspace {
    grid-template-columns: 1fr;
  }

  .puzzle-sheet {
    max-width: 42rem;
    margin-inline: auto;
  }

  .editorial-notes {
    grid-template-columns: repeat(2, 1fr);
    padding-top: 0;
  }

  .status-card,
  blockquote {
    grid-column: 1 / -1;
  }
}

@media (max-width: 45rem) {
  .page-shell {
    width: min(100% - 1rem, 42rem);
    min-height: calc(100vh - 1rem);
    margin: 0.5rem auto;
    padding: 1rem;
    background:
      linear-gradient(90deg, transparent 1.45rem, rgba(164, 59, 45, 0.12) 1.5rem, transparent 1.55rem),
      var(--paper-light);
  }

  .masthead {
    grid-template-columns: 4.5rem 1fr;
  }

  .masthead__marker {
    width: 4.5rem;
  }

  h1 {
    font-size: clamp(2.65rem, 15vw, 4.6rem);
  }

  .deck br {
    display: none;
  }

  .workspace {
    gap: 2.5rem;
    padding-block: 2rem;
  }

  .board-stage {
    padding: 0.5rem;
  }

  .board-stage__index {
    right: -0.2rem;
  }

  .cell input {
    font-size: clamp(1.15rem, 7vw, 2rem);
  }

  .cell.is-conflict::after {
    top: 0.08rem;
    right: 0.08rem;
    width: 0.78rem;
    height: 0.78rem;
    font-size: 0.52rem;
  }

  .actions {
    grid-template-columns: repeat(2, 1fr);
  }

  .button--primary {
    grid-column: 1 / -1;
  }

  .editorial-notes {
    grid-template-columns: 1fr;
  }

  .status-card,
  blockquote {
    grid-column: auto;
  }

  footer {
    display: grid;
  }
}

@media (max-width: 28rem) {
  .masthead {
    grid-template-columns: 1fr;
  }

  .masthead__marker {
    width: 4rem;
  }

  .masthead__rule {
    display: none;
  }

  .section-heading {
    align-items: start;
  }

  .progress-label {
    max-width: 5rem;
    text-align: right;
  }

  .legend {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    scroll-behavior: auto !important;
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

@media (prefers-contrast: more), (forced-colors: active) {
  .cell.is-related,
  .cell.is-peer-value {
    outline: 1px dashed currentColor;
    outline-offset: -3px;
  }

  .cell.is-conflict {
    outline: 4px solid var(--accent);
    outline-offset: -5px;
  }

  .button,
  .status-card {
    border: 2px solid currentColor;
  }
}