[hidden] { display: none !important; }
:root {
  --paper: #f7f5f0;
  --card: #ffffff;
  --ink: #1f1f1f;
  --muted: #5d5a52;
  --line: #d7d1c3;
  --grid: #b9b2a3;
  --blue: #2f5da8;
  --blue-soft: #e4ecf8;
  --warn: #b3261e;
  --warn-soft: #fbe7e5;
  --ok: #1d7a46;
  --hi: #fff1b8;
  --ca: #ffd9a8;
  --cb: #cfe0ff;
  --body: Inter, system-ui, -apple-system, "Segoe UI", Roboto, "Noto Sans", sans-serif;
}
@media (prefers-color-scheme: dark) {
  :root {
    --paper: #15171a;
    --card: #1e2125;
    --ink: #eceae4;
    --muted: #a8a49a;
    --line: #3a3d42;
    --grid: #565a61;
    --blue: #8fb3ff;
    --blue-soft: #232c3d;
    --warn: #ff8f86;
    --warn-soft: #3a2220;
    --ok: #6fd69b;
    --hi: #4a4120;
    --ca: #5a3e1b;
    --cb: #22345a;
  }
}
* { box-sizing: border-box; }
html { overflow-x: clip; -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--paper); color: var(--ink); font: 17px/1.7 var(--body); }
a { color: var(--blue); text-underline-offset: 3px; }
a:focus-visible, button:focus-visible, summary:focus-visible { outline: 3px solid var(--blue); outline-offset: 3px; }
img { max-width: 100%; height: auto; }
.wrap { max-width: 1120px; margin: 0 auto; padding-inline: 24px; }
.narrow { max-width: 780px; }

/* header */
.bar { display: flex; align-items: center; justify-content: space-between; gap: 16px; padding-block: 18px; flex-wrap: wrap; }
.brand { display: inline-flex; align-items: center; gap: 10px; font-weight: 700; color: var(--ink); text-decoration: none; font-size: 19px; }
.brand img { width: 30px; height: 30px; border-radius: 7px; }
.bar nav { display: flex; gap: 22px; flex-wrap: wrap; font-size: 15px; }
.bar nav a { color: var(--muted); text-decoration: none; padding-block: 4px; }
.bar nav a:hover, .bar nav a[aria-current="page"] { color: var(--ink); }
.bar nav a[aria-current="page"] { border-bottom: 2px solid var(--blue); }

/* footer */
footer { border-top: 1px solid var(--line); margin-top: 72px; padding-block: 28px 44px; font-size: 14px; color: var(--muted); }
footer .row { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 10px 28px; }
footer a { color: var(--muted); }
footer nav { display: flex; flex-wrap: wrap; gap: 8px 20px; }
.langs { display: flex; flex-wrap: wrap; gap: 6px 16px; margin-top: 18px; }
.langs span[aria-current] { color: var(--ink); font-weight: 600; }

/* type */
h1 { font-weight: 600; font-size: clamp(34px, 5.4vw, 58px); line-height: 1.12; letter-spacing: -.03em; margin: 16px 0 18px; }
h2 { font-weight: 600; font-size: clamp(24px, 3vw, 31px); line-height: 1.25; margin: 52px 0 14px; letter-spacing: -.01em; }
h3 { font-size: 20px; margin: 28px 0 8px; }
p, li { max-width: 74ch; }
.eyebrow { font-size: 13px; text-transform: uppercase; letter-spacing: .14em; color: var(--blue); font-weight: 600; margin: 0; }
.lead { font-size: 20px; color: var(--muted); max-width: 62ch; }
.crumbs { font-size: 14px; color: var(--muted); padding-top: 8px; }
.crumbs a { color: var(--muted); }
.crumbs .sep { margin-inline: 8px; }
.meta { font-size: 14px; color: var(--muted); margin: 0 0 24px; }

/* answer box */
.answer { background: var(--blue-soft); border-inline-start: 4px solid var(--blue); border-radius: 10px; padding: 18px 22px; margin: 26px 0 8px; }
.answer b { display: block; font-size: 13px; text-transform: uppercase; letter-spacing: .12em; color: var(--blue); margin-bottom: 6px; }
.answer p { margin: 0; }
.callout { background: var(--card); border: 1px solid var(--line); border-radius: 10px; padding: 14px 18px; margin: 20px 0; }

/* body lists */
.article ol, .article ul { padding-inline-start: 1.3em; }
.article li { margin: 6px 0; }

/* diagrams */
figure.fig { margin: 26px 0; }
figure.fig .scroll { overflow-x: auto; }
figure.fig figcaption { font-size: 15px; color: var(--muted); margin-top: 10px; max-width: 74ch; }
svg.dg { display: block; width: 100%; max-width: 640px; min-width: 460px; height: auto; background: var(--card); border: 1px solid var(--line); border-radius: 10px; }
svg.dg-map { max-width: 460px; min-width: 300px; }
svg.dg-xy { max-width: 600px; }
svg.dg .cell { fill: var(--card); stroke: var(--line); stroke-width: 1; }
svg.dg .cell.hi { fill: var(--hi); }
svg.dg .cell.ca { fill: var(--ca); }
svg.dg .cell.cb { fill: var(--cb); }
svg.dg .cell.el { fill: var(--warn-soft); }
svg.dg .frame { fill: none; stroke: var(--ink); stroke-width: 2; }
svg.dg .line { stroke: var(--line); stroke-width: 1; }
svg.dg .line.thick { stroke: var(--ink); stroke-width: 2; }
svg.dg .gv { fill: var(--muted); font-weight: 600; }
svg.dg .cd { fill: var(--muted); font-weight: 500; }
svg.dg .cd.ky { fill: var(--blue); font-weight: 800; }
svg.dg .cd.ex { fill: var(--warn); font-weight: 800; text-decoration: line-through; }
svg.dg .lb { fill: var(--muted); }
.dg-note { font-size: 13px; color: var(--muted); }

/* buttons & cta */
.play img { height: 62px; width: auto; display: block; }
.btn { display: inline-flex; align-items: center; justify-content: center; gap: 8px; border: 1px solid var(--line); background: var(--card); color: var(--ink); border-radius: 10px; padding: 10px 16px; font: inherit; font-size: 15px; font-weight: 600; cursor: pointer; text-decoration: none; min-height: 44px; }
.btn:hover { border-color: var(--blue); }
.btn.primary { background: var(--blue); border-color: var(--blue); color: #fff; }
@media (prefers-color-scheme: dark) { .btn.primary { color: #0f1a2e; } }
.btn[aria-pressed="true"] { background: var(--blue-soft); border-color: var(--blue); color: var(--blue); }
.cta-box { display: grid; grid-template-columns: 180px 1fr; gap: 28px; align-items: center; background: var(--card); border: 1px solid var(--line); border-radius: 16px; padding: 24px; margin: 56px 0 0; }
.cta-box img { border-radius: 12px; border: 1px solid var(--line); width: 100%; }
.cta-box h2 { margin: 0 0 8px; font-size: 26px; }
.cta-box p { margin-top: 0; }
.badges { display: flex; align-items: center; gap: 16px; flex-wrap: wrap; }
.pill { font-size: 13px; color: var(--muted); }

/* faq */
.faq details { border-bottom: 1px solid var(--line); padding: 14px 0; }
.faq summary { cursor: pointer; font-weight: 600; list-style-position: outside; }
.faq details p { margin: 10px 0 0; }

/* cards */
ul.cards { list-style: none; margin: 0; padding: 0; display: grid; grid-template-columns: repeat(auto-fill, minmax(250px, 1fr)); gap: 14px; }
ul.cards li { max-width: none; margin: 0; }
ul.cards a { display: block; height: 100%; background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 16px 18px; text-decoration: none; color: var(--ink); }
ul.cards a:hover { border-color: var(--blue); }
ul.cards b { display: block; margin-bottom: 4px; }
ul.cards span { display: block; font-size: 14px; color: var(--muted); line-height: 1.5; }

/* home */
.hero { display: grid; grid-template-columns: 1.1fr .9fr; gap: 64px; align-items: center; padding-block: 36px 8px; }
.hero .lead { margin-bottom: 22px; }
.preview { max-width: 460px; width: 100%; }
.daily { font-size: 13px; color: var(--muted); margin: 0 0 10px; }
.board { display: grid; grid-template-columns: repeat(9, 1fr); grid-template-rows: repeat(9, 1fr); aspect-ratio: 1; background: var(--card); border: 3px solid var(--ink); border-radius: 12px; overflow: hidden; box-shadow: 0 10px 30px rgba(0,0,0,.10); }
.board .c, .board .cell { display: grid; place-items: center; min-width: 0; min-height: 0; margin: 0; padding: 0; border: 0; border-inline-end: 1px solid var(--grid); border-bottom: 1px solid var(--grid); font-size: clamp(16px, 3.4vw, 30px); font-weight: 600; font-variant-numeric: tabular-nums; line-height: 1; color: var(--ink); background: transparent; }
.board .c:nth-child(3n), .board .cell:nth-child(3n) { border-inline-end: 2px solid var(--ink); }
.board .c:nth-child(9n), .board .cell:nth-child(9n) { border-inline-end: 0; }
.board .c:nth-child(n+19):nth-child(-n+27), .board .c:nth-child(n+46):nth-child(-n+54), .board .cell:nth-child(n+19):nth-child(-n+27), .board .cell:nth-child(n+46):nth-child(-n+54) { border-bottom: 2px solid var(--ink); }
.board .c:nth-child(n+73), .board .cell:nth-child(n+73) { border-bottom: 0; }
.features { display: grid; grid-template-columns: repeat(3, 1fr); gap: 32px; margin-top: 56px; border-top: 1px solid var(--line); }
.features h3 { font-size: 21px; }
.screens { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; margin: 24px 0; }
.screens img { width: 100%; border: 1px solid var(--line); border-radius: 12px; }

/* tools */
.tool { background: var(--card); border: 1px solid var(--line); border-radius: 16px; padding: 20px; margin: 24px 0; }
.tool-bar { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; margin-bottom: 14px; }
.tool-bar .grow { flex: 1; }
.tool-stat { font-variant-numeric: tabular-nums; color: var(--muted); font-size: 15px; }
.tool-msg { min-height: 1.6em; margin: 12px 0 0; font-weight: 600; }
.tool-msg.ok { color: var(--ok); }
.tool-msg.bad { color: var(--warn); }
.play-grid { display: grid; grid-template-columns: minmax(280px, 520px) 1fr; gap: 28px; align-items: start; }
.sb { display: grid; grid-template-columns: repeat(9, 1fr); border: 2px solid var(--ink); aspect-ratio: 1; width: 100%; max-width: 520px; background: var(--card); user-select: none; -webkit-user-select: none; touch-action: manipulation; }
.sb .k { position: relative; display: grid; place-items: center; border: 0; border-inline-end: 1px solid var(--line); border-bottom: 1px solid var(--line); background: transparent; color: var(--ink); font: inherit; font-size: clamp(18px, 4.6vw, 30px); padding: 0; cursor: pointer; border-radius: 0; }
.sb .k:nth-child(3n) { border-inline-end: 2px solid var(--ink); }
.sb .k:nth-child(n+19):nth-child(-n+27), .sb .k:nth-child(n+46):nth-child(-n+54) { border-bottom: 2px solid var(--ink); }
.sb .k.given { font-weight: 700; }
.sb .k.user { color: var(--blue); }
.sb .k.rel { background: var(--blue-soft); }
.sb .k.same { background: var(--hi); }
.sb .k.sel { background: var(--ca); outline: 2px solid var(--blue); outline-offset: -2px; z-index: 1; }
.sb .k.err { color: var(--warn); background: var(--warn-soft); }
.sb .k.hint { box-shadow: inset 0 0 0 3px var(--ok); }
.sb .k .nt { display: grid; grid-template-columns: repeat(3, 1fr); width: 100%; height: 100%; font-size: clamp(8px, 1.9vw, 12px); line-height: 1; color: var(--muted); padding: 2px; }
.sb .k .nt i { font-style: normal; display: grid; place-items: center; }
.sb .k .nt i.x { color: var(--warn); font-weight: 800; text-decoration: line-through; }
.sb .k .nt i.y { color: var(--blue); font-weight: 800; }
.sb .k.sel .nt { color: var(--ink); }
.pad { display: grid; grid-template-columns: repeat(9, 1fr); gap: 6px; margin-top: 14px; max-width: 520px; }
.pad .btn { padding: 8px 0; font-size: 20px; min-height: 48px; }
.pad .btn small { display: block; font-size: 10px; color: var(--muted); font-weight: 500; line-height: 1; }
.side h3 { margin-top: 0; }
.sol-input .k { font-size: clamp(18px, 4.6vw, 28px); }
.sol-input .k input { width: 100%; height: 100%; border: 0; background: transparent; color: inherit; font: inherit; text-align: center; padding: 0; min-width: 0; -moz-appearance: textfield; }
.sol-input .k input:focus { outline: 2px solid var(--blue); outline-offset: -2px; background: var(--ca); }
.sol-input .k.out input { color: var(--blue); font-weight: 600; }
.sol-input .k.err input { color: var(--warn); background: var(--warn-soft); }
.print-opts { display: flex; flex-wrap: wrap; gap: 14px 18px; align-items: end; margin-bottom: 18px; }
.print-opts label { display: grid; gap: 4px; font-size: 14px; color: var(--muted); }
.print-opts select { font: inherit; padding: 9px 10px; border: 1px solid var(--line); border-radius: 8px; background: var(--card); color: var(--ink); min-height: 44px; }
.sheet { display: grid; grid-template-columns: repeat(2, 1fr); gap: 28px; }
.sheet .pz h4 { margin: 0 0 6px; font-size: 14px; color: var(--muted); font-weight: 600; }
.sheet .board { max-width: 340px; margin: 0; }
.sheet .board .c { font-size: clamp(14px, 2.2vw, 21px); }

@media (max-width: 860px) {
  .hero, .features, .screens, .play-grid { grid-template-columns: 1fr; gap: 24px; }
  .cta-box { grid-template-columns: 1fr; }
  .cta-box img { max-width: 200px; }
  .sheet { grid-template-columns: 1fr; }
  .wrap { padding-inline: 18px; }
  .pad { gap: 4px; }
}
@media print {
  .bar, footer, .crumbs, .answer, .cta-box, .faq, .related, .no-print, .print-opts, .article > h1, .article > .lead, .article > h2, .article > p, .article > ul, .article > ol, .article > figure { display: none !important; }
  body { background: #fff; color: #000; font-size: 12pt; }
  .tool { border: 0; padding: 0; margin: 0; }
  .sheet { gap: 18mm 12mm; }
  .sheet .pz { break-inside: avoid; }
  .sheet .board { max-width: 80mm; border-color: #000; }
  .sheet .board .c { border-color: #888; color: #000; }
}