/* Sudoku Atelier — design system
   Ink-on-paper light theme, deep-slate dark theme. No webfonts, no frameworks. */

:root {
  --bg: #f7f4ef;
  --bg-elev: #fffdf9;
  --ink: #1c1a17;
  --ink-soft: #4a453d;
  --ink-mute: #7b7468;
  --line: #d9d2c6;
  --line-strong: #b6ac9c;
  --accent: #b4531f;
  --accent-soft: #f3e2d6;
  --accent-ink: #8a3c12;
  --good: #2f6b4f;
  --bad: #a12f2f;
  --given: #1c1a17;
  --entered: #1f4e7a;
  --note: #6b6458;
  --cell-bg: #fffdf9;
  --cell-bg-alt: #f1ece3;
  --cell-sel: #f6d9c4;
  --cell-peer: #f2ece1;
  --cell-same: #e6eef4;
  --shadow: 0 1px 2px rgba(28, 26, 23, .06), 0 8px 24px rgba(28, 26, 23, .05);
  --radius: 10px;
  --maxw: 1080px;
  --font-ui: ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif;
  --font-display: ui-serif, "Iowan Old Style", "Palatino Linotype", Palatino, Georgia, "Times New Roman", serif;
}

[data-theme="dark"] {
  --bg: #14161a;
  --bg-elev: #1b1e24;
  --ink: #e9e6df;
  --ink-soft: #b9b3a7;
  --ink-mute: #857f74;
  --line: #2c313a;
  --line-strong: #3d444f;
  --accent: #e08a4e;
  --accent-soft: #33251c;
  --accent-ink: #f0a36b;
  --good: #6fbf92;
  --bad: #e07070;
  --given: #e9e6df;
  --entered: #87b7e6;
  --note: #9a9384;
  --cell-bg: #1b1e24;
  --cell-bg-alt: #22262e;
  --cell-sel: #3a2a1e;
  --cell-peer: #242a33;
  --cell-same: #1f2a33;
  --shadow: 0 1px 2px rgba(0, 0, 0, .4), 0 8px 24px rgba(0, 0, 0, .35);
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font-ui);
  font-size: 16px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--accent-ink); text-decoration-thickness: 1px; text-underline-offset: 2px; }
a:hover { color: var(--accent); }

.wrap { max-width: var(--maxw); margin: 0 auto; padding: 0 20px; }

/* ---------- header ---------- */
.site-header {
  border-bottom: 1px solid var(--line);
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: saturate(1.2) blur(8px);
  position: sticky; top: 0; z-index: 40;
}
.site-header .wrap { display: flex; align-items: center; gap: 18px; height: 60px; }
.brand { display: inline-flex; align-items: center; gap: 10px; font-family: var(--font-display); font-size: 20px; font-weight: 600; color: var(--ink); text-decoration: none; letter-spacing: .2px; }
.brand svg { display: block; }
.brand b { font-weight: 700; }
.nav { display: flex; gap: 18px; margin-left: auto; align-items: center; }
.nav a { color: var(--ink-soft); text-decoration: none; font-size: 14.5px; }
.nav a:hover { color: var(--ink); }
.nav a[aria-current="page"] { color: var(--accent-ink); font-weight: 600; }
.icon-btn {
  display: inline-grid; place-items: center; width: 36px; height: 36px; border-radius: 9px;
  border: 1px solid var(--line); background: var(--bg-elev); color: var(--ink-soft); cursor: pointer;
}
.icon-btn:hover { border-color: var(--line-strong); color: var(--ink); }
@media (max-width: 700px) { .nav .hide-sm { display: none; } }

/* ---------- hero ---------- */
.hero { padding: 40px 0 18px; }
.hero h1 { font-family: var(--font-display); font-size: clamp(30px, 4.4vw, 46px); line-height: 1.12; margin: 0 0 12px; letter-spacing: -.5px; }
.hero p.lede { font-size: 17.5px; color: var(--ink-soft); max-width: 62ch; margin: 0 0 18px; }
.eyebrow { display: inline-block; font-size: 12.5px; letter-spacing: .12em; text-transform: uppercase; color: var(--accent-ink); font-weight: 600; margin-bottom: 10px; }

/* ---------- layout ---------- */
.split { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1.05fr); gap: 36px; align-items: start; }
@media (max-width: 900px) { .split { grid-template-columns: minmax(0, 1fr); gap: 24px; } }
.split > * { min-width: 0; }
@media (max-width: 620px) {
  .nav { gap: 12px; }
  .nav a { font-size: 13.5px; }
  .nav a.hide-sm, .nav a.hide-xs { display: none; }
  .brand span { font-size: 17px; }
  .toolbar { gap: 6px; }
  .btn { padding: 9px 11px; font-size: 13.5px; }
}

.section { padding: 34px 0; border-top: 1px solid var(--line); }
.section h2 { font-family: var(--font-display); font-size: clamp(22px, 2.6vw, 30px); margin: 0 0 8px; letter-spacing: -.3px; }
.section p.sub { color: var(--ink-soft); margin: 0 0 22px; max-width: 70ch; }

/* ---------- cards ---------- */
.cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(210px, 1fr)); gap: 14px; }
.card {
  display: block; padding: 18px; background: var(--bg-elev); border: 1px solid var(--line);
  border-radius: var(--radius); text-decoration: none; color: inherit; box-shadow: var(--shadow);
  transition: transform .12s ease, border-color .12s ease;
}
.card:hover { transform: translateY(-2px); border-color: var(--line-strong); color: inherit; }
.card h3 { margin: 0 0 4px; font-size: 17px; }
.card p { margin: 0; color: var(--ink-mute); font-size: 14px; }
.card .dots { display: flex; gap: 4px; margin-top: 10px; }
.card .dots i { width: 18px; height: 4px; border-radius: 2px; background: var(--line-strong); }
.card .dots i.on { background: var(--accent); }

/* ---------- board ---------- */
.board-wrap { position: relative; }
.board {
  display: grid;
  /* 用百分比而非 1fr：fr 在"高度由 aspect-ratio 推导"时会被当作 auto，
     导致行高按内容取整（底行短 1px、格子非正方）。calc(100%/9) 在确定尺寸下逐格精确。 */
  grid-template-columns: repeat(9, calc(100% / 9));
  grid-template-rows: repeat(9, calc(100% / 9));
  gap: 0;
  width: min(100%, 540px); aspect-ratio: 1 / 1;
  background: var(--cell-bg); border: 2px solid var(--ink);
  border-radius: 6px; overflow: hidden; user-select: none; touch-action: manipulation;
  position: relative;
}
.cell {
  position: relative; display: grid; place-items: center;
  min-width: 0; min-height: 0;   /* 内容不得撑大轨道 */
  font-size: clamp(18px, 3.6vw, 28px); font-weight: 500;
  border-right: 1px solid var(--line); border-bottom: 1px solid var(--line);
  background: var(--cell-bg); color: var(--entered); cursor: pointer;
  transition: background-color .08s linear;
}
.cell:nth-child(9n) { border-right: 0; }
.cell:nth-child(n+73) { border-bottom: 0; }
/* 3×3 粗分隔线：用叠加层绘制，2px 实心，不占用单元格空间、不受 DPR 取整影响 */
.board::before, .board::after {
  content: ""; position: absolute; inset: 0; pointer-events: none; z-index: 2;
}
.board::before {
  background-image:
    linear-gradient(to right, transparent calc(100% / 3 - 1px), var(--ink) calc(100% / 3 - 1px), var(--ink) calc(100% / 3 + 1px), transparent calc(100% / 3 + 1px)),
    linear-gradient(to right, transparent calc(200% / 3 - 1px), var(--ink) calc(200% / 3 - 1px), var(--ink) calc(200% / 3 + 1px), transparent calc(200% / 3 + 1px));
}
.board::after {
  background-image:
    linear-gradient(to bottom, transparent calc(100% / 3 - 1px), var(--ink) calc(100% / 3 - 1px), var(--ink) calc(100% / 3 + 1px), transparent calc(100% / 3 + 1px)),
    linear-gradient(to bottom, transparent calc(200% / 3 - 1px), var(--ink) calc(200% / 3 - 1px), var(--ink) calc(200% / 3 + 1px), transparent calc(200% / 3 + 1px));
}
.cell.given { color: var(--given); font-weight: 650; }
.cell.peer { background: var(--cell-peer); }
.cell.same { background: var(--cell-same); }
.cell.sel { background: var(--cell-sel); box-shadow: inset 0 0 0 2px var(--accent); }
.cell.conflict { color: var(--bad); }
.cell.hint { animation: pulse 1.1s ease 2; }
@keyframes pulse { 0%,100% { background: var(--cell-bg); } 50% { background: var(--accent-soft); } }
.cell .notes { position: absolute; inset: 2px; display: grid; grid-template-columns: repeat(3, 1fr); grid-template-rows: repeat(3, 1fr); font-size: 9.5px; color: var(--note); font-weight: 500; line-height: 1; }
.cell .notes span { display: grid; place-items: center; }

/* ---------- controls ---------- */
.toolbar { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 14px; }
.btn {
  display: inline-flex; align-items: center; gap: 7px; padding: 9px 14px; border-radius: 9px;
  border: 1px solid var(--line); background: var(--bg-elev); color: var(--ink);
  font: inherit; font-size: 14px; cursor: pointer; text-decoration: none;
}
.btn:hover { border-color: var(--line-strong); }
.btn.primary { background: var(--accent); border-color: var(--accent); color: #fff; font-weight: 600; }
[data-theme="dark"] .btn.primary { color: #1b1207; }
.btn.primary:hover { filter: brightness(1.06); }
.btn.ghost { background: transparent; }
.btn:disabled { opacity: .45; cursor: not-allowed; }
.btn.on { border-color: var(--accent); color: var(--accent-ink); background: var(--accent-soft); }
.btn .kbd { font-size: 11px; opacity: .6; border: 1px solid currentColor; border-radius: 4px; padding: 0 3px; }

.status-row { display: flex; flex-wrap: wrap; gap: 16px; align-items: center; margin-top: 12px; font-size: 14px; color: var(--ink-mute); }
.status-row b { color: var(--ink); font-variant-numeric: tabular-nums; }

.numpad { display: grid; grid-template-columns: repeat(5, 1fr); gap: 8px; margin-top: 12px; max-width: 540px; }
.numpad button { padding: 14px 0; font-size: 20px; justify-content: center; }
@media (min-width: 901px) { .numpad { display: none; } }

/* ---------- hint box ---------- */
.hintbox {
  margin-top: 14px; padding: 14px 16px; border-left: 3px solid var(--accent);
  background: var(--accent-soft); border-radius: 0 8px 8px 0; font-size: 14.5px;
  max-width: 540px;
}
.hintbox strong { color: var(--accent-ink); }
.hintbox[hidden] { display: none; }

/* ---------- legend / list ---------- */
.tech-list { display: flex; flex-wrap: wrap; gap: 8px; padding: 0; list-style: none; margin: 10px 0 0; }
.pill { display: inline-block; padding: 3px 10px; border-radius: 999px; border: 1px solid var(--line); font-size: 12.5px; color: var(--ink-soft); background: var(--bg-elev); }

.grid-links { display: grid; grid-template-columns: repeat(auto-fill, minmax(66px, 1fr)); gap: 8px; margin: 16px 0 0; padding: 0; list-style: none; }
.grid-links a { display: block; padding: 9px 0; text-align: center; border: 1px solid var(--line); border-radius: 8px; text-decoration: none; color: var(--ink-soft); font-size: 13.5px; background: var(--bg-elev); font-variant-numeric: tabular-nums; }
.grid-links a:hover { border-color: var(--accent); color: var(--accent-ink); }
.grid-links a.cur { border-color: var(--accent); background: var(--accent-soft); color: var(--accent-ink); font-weight: 600; }

.pager { display: flex; justify-content: space-between; align-items: center; gap: 12px; margin-top: 26px; }
.pager a, .pager span { font-size: 14px; }

/* ---------- footer ---------- */
.site-footer { border-top: 1px solid var(--line); margin-top: 40px; padding: 28px 0 40px; color: var(--ink-mute); font-size: 13.5px; }
.site-footer .cols { display: flex; flex-wrap: wrap; gap: 28px; justify-content: space-between; }
.site-footer a { color: var(--ink-soft); text-decoration: none; }
.site-footer a:hover { color: var(--ink); text-decoration: underline; }
.site-footer nav { display: flex; flex-wrap: wrap; gap: 14px; }

/* ---------- prose ---------- */
.prose { max-width: 72ch; }
.prose h2 { font-family: var(--font-display); font-size: 27px; margin: 34px 0 10px; }
.prose h3 { font-size: 18.5px; margin: 26px 0 8px; }
.prose p, .prose li { color: var(--ink-soft); }
.prose code { background: var(--cell-bg-alt); padding: 1px 5px; border-radius: 4px; font-size: 90%; }
.prose table { border-collapse: collapse; width: 100%; margin: 16px 0; font-size: 14.5px; }
.prose th, .prose td { border-bottom: 1px solid var(--line); padding: 8px 10px; text-align: left; }
.prose th { color: var(--ink); font-weight: 600; }
.prose blockquote { margin: 18px 0; padding: 10px 16px; border-left: 3px solid var(--accent); background: var(--accent-soft); border-radius: 0 8px 8px 0; }
.prose blockquote p { margin: 0; color: var(--ink); }

/* ---------- overlay ---------- */
.overlay {
  position: fixed; inset: 0; background: rgba(12, 11, 9, .55); display: grid; place-items: center;
  z-index: 60; padding: 20px; backdrop-filter: blur(3px);
}
.overlay[hidden] { display: none; }
.dialog { background: var(--bg-elev); border: 1px solid var(--line); border-radius: 16px; padding: 26px; max-width: 420px; width: 100%; box-shadow: var(--shadow); }
.dialog h2 { margin: 0 0 6px; font-family: var(--font-display); font-size: 26px; }
.dialog p { color: var(--ink-soft); margin: 0 0 16px; }
.dialog .stats { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin: 16px 0; }
.dialog .stats div { background: var(--cell-bg-alt); border-radius: 10px; padding: 10px 12px; }
.dialog .stats b { display: block; font-size: 20px; font-variant-numeric: tabular-nums; }
.dialog .stats span { font-size: 12px; color: var(--ink-mute); text-transform: uppercase; letter-spacing: .08em; }

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

@media (prefers-reduced-motion: reduce) {
  * { animation: none !important; transition: none !important; }
}

/* ---------- print ---------- */
@media print {
  .site-header, .site-footer, .toolbar, .numpad, .hintbox, .pager, .no-print, .overlay { display: none !important; }
  body { background: #fff; color: #000; }
  .board { width: 15cm; border: 2px solid #000; }
  .cell { border-color: #999; color: #000; font-size: 16pt; }
  .cell.given { color: #000; font-weight: 700; }
  .split { display: block; }
  .prose, .hero p { color: #000; }
  a[href]::after { content: ""; }
}

/* ---------- interactive technique player ---------- */
.board.mini { width: min(100%, 360px); }
.player { margin: 26px 0 8px; padding: 18px; border: 1px solid var(--line); border-radius: 14px; background: var(--bg-elev); }
.player .board { margin: 0 auto; }
.player-bar { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; margin-top: 14px; }
.player-bar .btn { padding: 7px 12px; font-size: 13.5px; }
.player-count { font-size: 13px; color: var(--ink-mute); font-variant-numeric: tabular-nums; margin: 0 4px; }
.player-progress { height: 3px; background: var(--line); border-radius: 2px; margin-top: 10px; overflow: hidden; }
.player-progress i { display: block; height: 100%; width: 0; background: var(--accent); transition: width .15s ease; }
.player-caption { margin: 12px 0 0; font-size: 14.5px; color: var(--ink-soft); min-height: 3em; }
.player-caption strong { color: var(--accent-ink); }
.cell.hl { background: var(--accent-soft); box-shadow: inset 0 0 0 2px var(--accent); }
.cell.elim { background: var(--cell-same); }
.cell.elim::after { content: ""; position: absolute; inset: 30%; border: 1.5px dashed var(--ink-mute); border-radius: 4px; opacity: .55; }
.player .cell { font-size: clamp(14px, 2.6vw, 20px); }

/* 表格在正文中的可读性 */
.prose table { font-size: 14px; }
.prose table td, .prose table th { padding: 7px 9px; }
.prose ul li, .prose ol li { margin: 4px 0; }
.prose h2 { scroll-margin-top: 80px; }
.prose h3 { scroll-margin-top: 80px; }

/* 标题断行更自然 */
.hero h1, .prose h1, .section h2 { text-wrap: balance; }