/* =================================================================
   sudoku.tips — "modern broadsheet" design system
   Warm paper · ink black · pencil-red accent · refined serif display
   ================================================================= */

:root {
  /* Palette */
  --paper:      #f4efe4;
  --paper-2:    #ece5d4;
  --ink:        #1b1a17;
  --ink-soft:   #4a4640;
  --ink-faint:  #5c5546;   /* AA-contrast (>=4.5) on paper, paper-2 & card */
  --line:       #cdc4b0;
  --line-soft:  #ddd5c2;
  --accent:     #c0362c;   /* pencil / proof-reader red */
  --accent-dk:  #99291f;
  --blue:       #2c4a7c;   /* given-number ink-blue */
  --gold:       #b88a2e;
  --good:       #3f6e3a;
  --card:       #fbf8f0;
  --shadow:     22, 20, 16;

  /* Type */
  --display: "Fraunces", Georgia, "Times New Roman", serif;
  --body: ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto,
          "Helvetica Neue", "Hiragino Kaku Gothic ProN", "Yu Gothic UI",
          "Microsoft YaHei", "Malgun Gothic", "Noto Sans", sans-serif;
  --num: "Fraunces", Georgia, serif;

  --maxw: 1120px;
  --radius: 4px;
}

* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }

body {
  font-family: var(--body);
  color: var(--ink);
  background-color: var(--paper);
  background-image:
    radial-gradient(circle at 12% -10%, rgba(192,54,44,.05), transparent 36%),
    radial-gradient(circle at 90% 8%, rgba(44,74,124,.05), transparent 40%),
    url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='120' height='120'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='.9' numOctaves='2'/%3E%3CfeColorMatrix type='saturate' values='0'/%3E%3C/filter%3E%3Crect width='120' height='120' filter='url(%23n)' opacity='.035'/%3E%3C/svg%3E");
  line-height: 1.6;
  font-size: 17px;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}

.wrap { max-width: var(--maxw); margin: 0 auto; padding: 0 24px; }
a { color: var(--accent); text-decoration: none; }
a:hover { color: var(--accent-dk); }
::selection { background: var(--accent); color: var(--paper); }

/* ---------- Masthead ---------- */
.masthead {
  border-bottom: 2px solid var(--ink);
  background: var(--paper);
  position: sticky; top: 0; z-index: 50;
}
.masthead .wrap {
  display: flex; align-items: center; justify-content: space-between;
  gap: 18px; padding-top: 14px; padding-bottom: 14px;
}
.brand { display: flex; align-items: center; gap: 12px; }
.brand .mark { width: 34px; height: 34px; flex: none; }
.brand .name {
  font-family: var(--display); font-weight: 600; font-size: 1.5rem;
  letter-spacing: -.02em; color: var(--ink); line-height: 1;
}
.brand .name b { color: var(--accent); font-weight: 600; }
.brand .tag {
  font-size: .66rem; letter-spacing: .22em; text-transform: uppercase;
  color: var(--ink-faint); margin-top: 3px;
}
.nav { display: flex; align-items: center; gap: 26px; }
.nav a {
  color: var(--ink-soft); font-weight: 500; font-size: .92rem;
  letter-spacing: .01em; position: relative; padding: 2px 0;
}
.nav a::after {
  content: ""; position: absolute; left: 0; bottom: -3px; height: 2px;
  width: 0; background: var(--accent); transition: width .25s ease;
}
.nav a:hover { color: var(--ink); }
.nav a:hover::after { width: 100%; }

/* language menu */
.langbox { position: relative; }
.langbtn {
  display: inline-flex; align-items: center; gap: 7px; cursor: pointer;
  border: 1px solid var(--line); background: var(--card); color: var(--ink);
  padding: 7px 12px; border-radius: var(--radius); font: inherit;
  font-size: .85rem; font-weight: 600;
}
.langbtn:hover { border-color: var(--ink); }
.langbtn svg { width: 14px; height: 14px; }
.langmenu {
  position: absolute; right: 0; top: calc(100% + 8px); min-width: 200px;
  background: var(--card); border: 1px solid var(--line);
  border-radius: var(--radius); box-shadow: 0 18px 40px -16px rgba(var(--shadow),.4);
  padding: 6px; display: none; z-index: 60;
}
.langmenu.open { display: block; }
.langmenu a {
  display: flex; justify-content: space-between; gap: 16px;
  padding: 8px 12px; color: var(--ink-soft); border-radius: 3px;
  font-size: .9rem;
}
.langmenu a:hover { background: var(--paper-2); color: var(--ink); }
.langmenu a[aria-current="true"] { color: var(--accent); font-weight: 600; }
.langmenu a .en { color: var(--ink-faint); font-size: .78rem; }

.burger { display: none; background: none; border: 0; cursor: pointer; }
.burger span { display: block; width: 24px; height: 2px; background: var(--ink); margin: 5px 0; transition: .25s; }

/* ---------- Hero / play ---------- */
.hero { padding: 46px 0 30px; }
.hero .wrap { display: grid; grid-template-columns: 1.05fr 1.15fr; gap: 56px; align-items: start; }
.kicker {
  display: inline-flex; align-items: center; gap: 9px;
  font-size: .72rem; letter-spacing: .2em; text-transform: uppercase;
  color: var(--accent); font-weight: 700; margin-bottom: 18px;
}
.kicker::before { content: ""; width: 26px; height: 1px; background: var(--accent); }
.hero h1 {
  font-family: var(--display); font-weight: 600; font-size: clamp(2.5rem, 5.4vw, 4rem);
  line-height: .98; letter-spacing: -.025em; color: var(--ink);
  margin-bottom: 20px;
}
.hero h1 em { font-style: italic; color: var(--accent); }
.hero .lead { font-size: 1.12rem; color: var(--ink-soft); max-width: 46ch; margin-bottom: 26px; }
.hero .stats { display: flex; gap: 34px; margin-top: 30px; padding-top: 26px; border-top: 1px solid var(--line); }
.hero .stats .n { font-family: var(--display); font-size: 1.9rem; font-weight: 600; line-height: 1; color: var(--ink); }
.hero .stats .l { font-size: .76rem; letter-spacing: .08em; text-transform: uppercase; color: var(--ink-faint); margin-top: 6px; }

/* hero animation on load */
.reveal { opacity: 0; transform: translateY(14px); animation: rise .7s cubic-bezier(.2,.7,.3,1) forwards; }
.reveal.d1 { animation-delay: .05s; }
.reveal.d2 { animation-delay: .14s; }
.reveal.d3 { animation-delay: .23s; }
.reveal.d4 { animation-delay: .32s; }
@keyframes rise { to { opacity: 1; transform: none; } }
@media (prefers-reduced-motion: reduce) { .reveal { animation: none; opacity: 1; transform: none; } }

/* ---------- Sudoku board card ---------- */
.play-card {
  background: var(--card); border: 1px solid var(--line);
  border-radius: 8px; padding: 20px;
  box-shadow: 0 30px 60px -34px rgba(var(--shadow),.55), 0 2px 0 var(--line-soft);
  position: relative;
}
.play-head { display: flex; align-items: center; justify-content: space-between; margin-bottom: 14px; gap: 12px; flex-wrap: wrap; }
.diff-tabs { display: inline-flex; background: var(--paper-2); border: 1px solid var(--line-soft); border-radius: 999px; padding: 3px; }
.diff-tabs button {
  border: 0; background: none; cursor: pointer; font: inherit; font-size: .8rem; font-weight: 600;
  color: var(--ink-soft); padding: 6px 13px; border-radius: 999px; transition: .2s; white-space: nowrap;
}
.diff-tabs button.active { background: var(--ink); color: var(--paper); }
.meta { display: flex; align-items: center; gap: 16px; font-variant-numeric: tabular-nums; }
.meta .item { display: flex; flex-direction: column; align-items: flex-end; }
.meta .item .lab { font-size: .62rem; letter-spacing: .12em; text-transform: uppercase; color: var(--ink-faint); }
.meta .item .val { font-family: var(--num); font-size: 1.18rem; font-weight: 600; color: var(--ink); line-height: 1; }
.meta .val.warn { color: var(--accent); }

/* the grid */
.board-frame { position: relative; }
.board {
  display: grid; grid-template-columns: repeat(9, 1fr); grid-template-rows: repeat(9, 1fr);
  aspect-ratio: 1/1;
  background: var(--card); border: 2.5px solid var(--ink);
  border-radius: 3px; overflow: hidden; touch-action: manipulation;
  user-select: none;
}
/* Grid lines are real cell borders (no gap, no box-shadow, cream board bg) so
   the board can never flash black between cells on re-layout, and no cell gets
   a compositing layer WebKit could leave behind as a stale highlight. */
.cell {
  background: var(--card); display: flex; align-items: center; justify-content: center;
  min-width: 0; min-height: 0; box-sizing: border-box;
  border-right: 1px solid var(--line-soft); border-bottom: 1px solid var(--line-soft);
  font-family: var(--num); font-size: clamp(1.1rem, 4.2vw, 1.7rem); font-weight: 500;
  cursor: pointer; position: relative; color: var(--blue);
}
.cell.col  { border-right: 2px solid var(--ink); }
.cell.band { border-bottom: 2px solid var(--ink); }
.cell.band.col { border-right: 2px solid var(--ink); border-bottom: 2px solid var(--ink); }
.cell:nth-child(9n)   { border-right: 0; }
.cell:nth-child(n+73) { border-bottom: 0; }
.cell.given { color: var(--ink); font-weight: 600; }
.cell.user { color: var(--accent); }
.cell.peer { background: #efe9da; }
.cell.same { background: #e3dcc8; }
.cell.sel { background: #f6e3c6; outline: 2px solid var(--gold); outline-offset: -2px; }
.cell.err { color: #fff; background: var(--accent); }
.cell.flash { animation: flash .5s ease; }
@keyframes flash { 0%,100%{ background: var(--card); } 40%{ background: #d8efd4; } }
.cell .notes {
  position: absolute; inset: 0; display: grid; grid-template-columns: repeat(3,1fr);
  grid-template-rows: repeat(3,1fr); font-size: .52rem; color: var(--ink-faint);
  font-family: var(--body); font-weight: 600;
}
.cell .notes span { display: flex; align-items: center; justify-content: center; }

/* controls */
.controls { margin-top: 16px; }
.pad { display: grid; grid-template-columns: repeat(9, 1fr); gap: 6px; }
.pad button {
  font-family: var(--num); font-size: 1.25rem; font-weight: 600; color: var(--ink);
  background: var(--paper-2); border: 1px solid var(--line-soft); border-radius: var(--radius);
  padding: 12px 0; cursor: pointer; transition: .15s; position: relative;
}
.pad button:hover { background: var(--ink); color: var(--paper); border-color: var(--ink); }
.pad button .left { position: absolute; top: 3px; right: 5px; font-size: .56rem; font-weight: 700; color: var(--ink-faint); font-family: var(--body); }
.pad button:hover .left { color: var(--paper-2); }
.pad button.done { opacity: .35; pointer-events: none; }

.tools { display: flex; gap: 8px; margin-top: 12px; flex-wrap: wrap; }
.tools button {
  flex: 1 1 0; min-width: 78px; display: inline-flex; align-items: center; justify-content: center; gap: 7px;
  font: inherit; font-size: .82rem; font-weight: 600; color: var(--ink-soft);
  background: var(--card); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 10px 6px; cursor: pointer; transition: .15s;
}
.tools button:hover { border-color: var(--ink); color: var(--ink); }
.tools button svg { width: 16px; height: 16px; }
.tools button.on { background: var(--gold); border-color: var(--gold); color: #fff; }
.tools button.on .badge { background:#fff; color:var(--gold); }
.tools button .badge {
  font-size: .6rem; background: var(--ink); color: var(--paper); border-radius: 3px;
  padding: 1px 5px; margin-left: 2px; font-family: var(--num);
}
.btn-primary {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  background: var(--accent); color: #fff; border: 0; border-radius: var(--radius);
  font: inherit; font-weight: 700; font-size: .95rem; padding: 13px 22px; cursor: pointer;
  box-shadow: 0 8px 22px -10px rgba(192,54,44,.7); transition: .15s;
}
.btn-primary:hover { background: var(--accent-dk); transform: translateY(-1px); }
.btn-ghost {
  display: inline-flex; align-items: center; gap: 8px; background: none; border: 1.5px solid var(--ink);
  color: var(--ink); border-radius: var(--radius); font: inherit; font-weight: 600; font-size: .95rem;
  padding: 11px 20px; cursor: pointer; transition: .15s;
}
.btn-ghost:hover { background: var(--ink); color: var(--paper); }
.hero .cta { display: flex; gap: 12px; flex-wrap: wrap; }

/* win overlay */
.win {
  position: absolute; inset: 0; background: var(--card);
  display: none; flex-direction: column; align-items: center; justify-content: center; text-align: center;
  border-radius: 8px; z-index: 5; padding: 24px;
}
.win.show { display: flex; animation: rise .4s ease; }
.win .seal {
  font-family: var(--display); font-style: italic; color: var(--accent); font-size: 1rem;
  letter-spacing: .04em; margin-bottom: 8px;
}
.win h3 { font-family: var(--display); font-size: 2.4rem; font-weight: 600; line-height: 1; margin-bottom: 10px; }
.win p { color: var(--ink-soft); margin-bottom: 22px; }
.win .time { font-family: var(--num); font-weight: 700; color: var(--ink); }

/* ---------- Section scaffolding ---------- */
section { padding: 64px 0; }
.section-head { max-width: 60ch; margin-bottom: 40px; }
.section-head .kicker { margin-bottom: 14px; }
.section-head h2 {
  font-family: var(--display); font-weight: 600; font-size: clamp(1.9rem, 4vw, 2.8rem);
  letter-spacing: -.02em; line-height: 1.04; color: var(--ink);
}
.section-head p { color: var(--ink-soft); margin-top: 14px; font-size: 1.05rem; }
.rule { border: 0; border-top: 1px solid var(--line); }

/* how-to steps */
.steps { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }
.step { background: var(--card); border: 1px solid var(--line); border-radius: 6px; padding: 26px; position: relative; }
.step .no { font-family: var(--display); font-size: 2.4rem; font-weight: 600; color: var(--line); line-height: 1; position: absolute; top: 18px; right: 22px; }
.step h3 { font-family: var(--display); font-size: 1.25rem; font-weight: 600; margin-bottom: 8px; padding-right: 40px; }
.step p { color: var(--ink-soft); font-size: .95rem; }

/* techniques */
.tech-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 18px; }
.tech {
  background: var(--card); border: 1px solid var(--line); border-radius: 6px; padding: 22px 24px;
  display: flex; gap: 18px; align-items: flex-start; transition: .2s;
}
.tech:hover { border-color: var(--ink); transform: translateY(-2px); box-shadow: 0 18px 40px -26px rgba(var(--shadow),.5); }
.tech .lvl { font-family: var(--num); font-size: .72rem; font-weight: 700; letter-spacing: .05em; text-transform: uppercase; color: #fff; background: var(--blue); padding: 3px 8px; border-radius: 3px; white-space: nowrap; flex: none; margin-top: 3px; }
.tech .lvl.e { background: var(--good); }
.tech .lvl.m { background: var(--gold); }
.tech .lvl.h { background: var(--accent); }
.tech h3 { font-family: var(--display); font-size: 1.18rem; font-weight: 600; margin-bottom: 5px; }
.tech p { color: var(--ink-soft); font-size: .93rem; }

/* feature strip */
.features { display: grid; grid-template-columns: repeat(4, 1fr); gap: 0; border: 1px solid var(--line); border-radius: 6px; overflow: hidden; background: var(--card); }
.feature { padding: 30px 26px; border-right: 1px solid var(--line); }
.feature:last-child { border-right: 0; }
.feature .ic { width: 30px; height: 30px; color: var(--accent); margin-bottom: 14px; }
.feature h3 { font-family: var(--display); font-size: 1.1rem; font-weight: 600; margin-bottom: 6px; }
.feature p { font-size: .9rem; color: var(--ink-soft); }

/* faq */
.faq { max-width: 820px; }
.qa { border-top: 1px solid var(--line); }
.qa:last-child { border-bottom: 1px solid var(--line); }
.qa summary {
  cursor: pointer; list-style: none; padding: 22px 4px; display: flex; justify-content: space-between;
  gap: 20px; align-items: center; font-family: var(--display); font-size: 1.22rem; font-weight: 600; color: var(--ink);
}
.qa summary::-webkit-details-marker { display: none; }
.qa summary .sign { flex: none; width: 22px; height: 22px; position: relative; }
.qa summary .sign::before, .qa summary .sign::after { content:""; position:absolute; background: var(--accent); transition:.25s; }
.qa summary .sign::before { top: 10px; left: 0; width: 22px; height: 2px; }
.qa summary .sign::after { top: 0; left: 10px; width: 2px; height: 22px; }
.qa[open] summary .sign::after { transform: rotate(90deg); opacity: 0; }
.qa .ans { padding: 0 4px 24px; color: var(--ink-soft); max-width: 70ch; }

/* CTA band */
.band { background: var(--ink); color: var(--paper); border-radius: 10px; padding: 56px; text-align: center; position: relative; overflow: hidden; }
.band::before { content:""; position:absolute; inset:0; background-image: radial-gradient(circle at 80% 120%, rgba(192,54,44,.35), transparent 50%); }
.band h2 { font-family: var(--display); font-size: clamp(1.8rem,4vw,2.6rem); font-weight: 600; position: relative; }
.band p { color: #cfc7b6; margin: 14px auto 28px; max-width: 52ch; position: relative; }
.band .btn-primary { position: relative; }

/* footer */
.foot { border-top: 2px solid var(--ink); padding: 50px 0 40px; margin-top: 30px; }
.foot .grid { display: grid; grid-template-columns: 1.4fr 1fr 1fr 1fr; gap: 36px; }
.foot .name { font-family: var(--display); font-size: 1.4rem; font-weight: 600; }
.foot .name b { color: var(--accent); }
.foot p { color: var(--ink-soft); font-size: .9rem; margin-top: 10px; max-width: 34ch; }
.foot h2 { font-family: var(--body); font-weight: 700; font-size: .72rem; letter-spacing: .14em; text-transform: uppercase; color: var(--ink-faint); margin-bottom: 14px; }
.foot ul { list-style: none; }
.foot ul li { margin-bottom: 9px; }
.foot ul a { color: var(--ink-soft); font-size: .92rem; }
.foot ul a:hover { color: var(--accent); }
.foot .bottom { margin-top: 44px; padding-top: 22px; border-top: 1px solid var(--line); display: flex; justify-content: space-between; flex-wrap: wrap; gap: 12px; color: var(--ink-faint); font-size: .82rem; }

/* ---------- Responsive ---------- */
@media (max-width: 900px) {
  .hero .wrap { grid-template-columns: 1fr; gap: 36px; }
  .play-card { order: -1; }
  .steps { grid-template-columns: 1fr; }
  .tech-grid { grid-template-columns: 1fr; }
  .features { grid-template-columns: repeat(2, 1fr); }
  .feature:nth-child(2) { border-right: 0; }
  .feature:nth-child(1), .feature:nth-child(2) { border-bottom: 1px solid var(--line); }
  .foot .grid { grid-template-columns: 1fr 1fr; }
}
@media (max-width: 680px) {
  .nav .nav-links { display: none; }
  .nav .nav-links.open { display: flex; }
  .burger { display: block; }
  body { font-size: 16px; }
  .features { grid-template-columns: 1fr; }
  .feature { border-right: 0 !important; border-bottom: 1px solid var(--line); }
  .feature:last-child { border-bottom: 0; }
  .foot .grid { grid-template-columns: 1fr; gap: 26px; }
  .band { padding: 40px 24px; }
  .pad button { font-size: 1.05rem; padding: 10px 0; }
  .hero { padding: 30px 0 10px; }
}

/* === sudoku.tips generated components (managed by build.py) === */
.skip-link{position:absolute;left:-999px;top:0;z-index:200;background:#1b1a17;color:#f4efe4;padding:.6em 1em}
.skip-link:focus{left:0}
.pagehero{padding-bottom:.5rem}
.pagehero h1{max-width:18ch}
.play-section{padding-top:.5rem}
.play-section .play-card{max-width:560px;margin:0 auto}
.crumbs{font-size:.8rem;color:#807a6c;padding:.9rem 0 0}
.crumbs ol{display:flex;flex-wrap:wrap;gap:.4em;list-style:none;margin:0;padding:0}
.crumbs li:not(:last-child)::after{content:"\203A";margin-left:.4em;color:#b3a78d}
.crumbs a{color:#807a6c;text-decoration:none}
.crumbs a:hover{color:#c0362c}
.prose{max-width:70ch}
.prose h2{font-size:1.5rem;margin:1.6em 0 .4em}
.prose h3{font-size:1.2rem;margin:1.3em 0 .3em}
.prose p,.prose li{line-height:1.65}
.prose ul,.prose ol{padding-left:1.3em}
.prose li{margin:.35em 0}
.note{border-left:3px solid #c0362c;background:rgba(192,54,44,.05);padding:.8rem 1.1rem;margin:1.3rem 0;border-radius:0 6px 6px 0}
.note p{margin:0}
.cardgrid{display:grid;gap:1rem;grid-template-columns:repeat(auto-fill,minmax(230px,1fr))}
.linkcard{display:block;border:1px solid #d8cfbc;border-radius:8px;padding:1.1rem 1.2rem;background:#fbf8f1;color:#1b1a17;text-decoration:none;transition:border-color .15s,box-shadow .15s}
.linkcard:hover{border-color:#c0362c;box-shadow:0 6px 20px rgba(27,26,23,.07)}
.linkcard h3{margin:0 0 .3em;font-size:1.15rem}
.linkcard p{margin:0 0 .6em;font-size:.93rem;color:#4a463d}
.linkcard .go{font-size:.82rem;color:#c0362c;font-weight:600}
.pillrow{display:flex;flex-wrap:wrap;gap:.5rem}
.pill{display:inline-block;padding:.45rem .95rem;border:1px solid #b3a78d;border-radius:100px;background:#f4efe4;color:#4a463d;font-size:.9rem;font-weight:500;text-decoration:none}
.pill:hover{border-color:#c0362c;color:#c0362c}
figure.diagram{margin:1.3rem 0}
figure.diagram figcaption{font-size:.85rem;color:#807a6c;margin-top:.5rem}
.minigrid{display:grid;grid-template-columns:repeat(9,1fr);gap:1px;background:#b3a78d;border:2px solid #1b1a17;width:100%;max-width:320px;aspect-ratio:1/1}
.minigrid .c{background:#fbf8f1;display:flex;align-items:center;justify-content:center;font-family:Georgia,serif;font-size:clamp(.7rem,3vw,1.05rem);color:#2c4a7c}
.minigrid .c.g{color:#1b1a17;font-weight:600}
.minigrid .c.mark{background:#f6d9b0;color:#c0362c;font-weight:700}
.minigrid .c.elim{background:#f6dcd8}
.minigrid .c.br{border-right:2px solid #1b1a17}
.minigrid .c.bb{border-bottom:2px solid #1b1a17}
.steps .step p{margin:0}
.section-head h2{margin:0}
/* === end generated components === */