/* Sudoku site styles.
   Both palettes are shipping in-app themes, taken verbatim from
   ~/Projects/sudoku/src/theme/index.ts:
     light = "pure"    (#FFFFFF page, #F2F2F7 card, #000000 ink, #2C4A7C accent,
                        #E5E5EA border, board lines #E0E0E5 / #86868C)
     dark  = "volcano" (#0E0F14 page, #181A24 card, #E0E0F0 ink, #FF4D1A accent,
                        #252840 border, board lines #2B2E3E / #5A5E80)
   No web fonts, no CDN, no client JS. */

:root {
  --bg: #FFFFFF;
  --panel: #F2F2F7;
  --panel-2: #E8E8ED;
  --line: #E5E5EA;
  --ink: #000000;
  --ink-dim: #3C3C43;
  --accent: #2C4A7C;
  --accent-2: #3D5F96;
  --btn-ink: #FFFFFF;
  --grid-line: #E0E0E5;
  --grid-box: #86868C;
  --cell-sel: #B2C5E3;
  --radius: 14px;
  --maxw: 1080px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0E0F14;
    --panel: #181A24;
    --panel-2: #1E2030;
    --line: #252840;
    --ink: #E0E0F0;
    --ink-dim: #9A9AC0;
    --accent: #FF6A3A;
    --accent-2: #FF4D1A;
    --btn-ink: #0E0F14;
    --grid-line: #2B2E3E;
    --grid-box: #5A5E80;
    --cell-sel: #5E2C13;
  }
}

* { box-sizing: border-box; }

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

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font: 16px/1.65 -apple-system, BlinkMacSystemFont, "Segoe UI", "Helvetica Neue",
        "Hiragino Sans", "Noto Sans CJK JP", "Apple SD Gothic Neo", Arial, sans-serif;
  overflow-wrap: break-word;
}

a { color: var(--accent); }

h1, h2, h3 { line-height: 1.25; letter-spacing: -0.01em; }

/* ---------------------------------------------------------- chrome */

.skip {
  position: absolute; left: -9999px; top: 0;
  background: var(--panel); color: var(--ink); padding: 10px 16px; z-index: 10;
}
.skip:focus { left: 8px; top: 8px; }

.topbar {
  display: flex; align-items: center; gap: 20px; flex-wrap: wrap;
  max-width: var(--maxw); margin: 0 auto; padding: 18px 20px;
}

.brand {
  display: inline-flex; align-items: center; gap: 9px;
  font-weight: 700; font-size: 19px; color: var(--ink); text-decoration: none;
}
.brand-mark {
  width: 28px; height: 28px; display: grid; place-items: center;
  border-radius: 8px; font-size: 15px;
  background: linear-gradient(150deg, var(--accent-2), var(--accent));
  color: var(--btn-ink);
}

.topnav { display: flex; gap: 18px; flex-wrap: wrap; margin-inline-start: auto; }
.topnav a { color: var(--ink-dim); text-decoration: none; font-size: 15px; }
.topnav a:hover { color: var(--ink); }

.btn {
  display: inline-block; background: var(--accent); color: var(--btn-ink);
  text-decoration: none; font-weight: 700; border-radius: 999px;
  padding: 13px 26px; border: 1px solid transparent;
}
.btn:hover { filter: brightness(1.08); }
.btn-small { padding: 8px 16px; font-size: 14px; }
.btn-big { font-size: 17px; }

/* ---------------------------------------------------------- hero */

.hero {
  max-width: var(--maxw); margin: 0 auto; padding: 40px 20px 12px;
  display: grid; gap: 40px; grid-template-columns: 1fr;
}
@media (min-width: 900px) {
  .hero { grid-template-columns: 1.05fr 0.95fr; align-items: center; padding-top: 64px; }
}

.kicker {
  margin: 0 0 10px; font-size: 13px; font-weight: 700; letter-spacing: 0.12em;
  text-transform: uppercase; color: var(--accent);
}
.hero h1 { margin: 0 0 18px; font-size: clamp(30px, 5.2vw, 50px); }
.lede { color: var(--ink-dim); font-size: 17px; margin: 0 0 26px; max-width: 60ch; }
.cta-row { margin: 0; }
.cta-note { color: var(--ink-dim); font-size: 14px; margin: 12px 0 0; }

/* A 9x9 grid drawn in CSS — no image, no request. The givens shown are a real
   puzzle position; the highlighted cell is the selection colour from the theme. */
.hero-art { display: flex; justify-content: center; }
.sd {
  width: 100%; max-width: 380px; padding: 10px;
  border-radius: 20px; border: 1px solid var(--line);
  background: var(--panel);
  box-shadow: 0 24px 60px rgba(0, 0, 0, 0.18);
}
.sd-grid {
  display: grid; grid-template-columns: repeat(9, 1fr);
  border: 2px solid var(--grid-box); border-radius: 6px; overflow: hidden;
  background: var(--bg);
}
.sd-cell {
  aspect-ratio: 1; display: grid; place-items: center;
  font-size: clamp(11px, 3.2vw, 17px); font-weight: 700; color: var(--ink);
  border-inline-end: 1px solid var(--grid-line);
  border-block-end: 1px solid var(--grid-line);
}
.sd-cell:nth-child(9n) { border-inline-end: 0; }
.sd-cell:nth-child(3n):not(:nth-child(9n)) { border-inline-end: 2px solid var(--grid-box); }
.sd-cell.r3 { border-block-end: 2px solid var(--grid-box); }
.sd-cell.r9 { border-block-end: 0; }
.sd-cell.u { color: var(--accent); font-weight: 600; }
.sd-cell.sel { background: var(--cell-sel); }

/* ---------------------------------------------------------- sections */

section { max-width: var(--maxw); margin: 0 auto; padding: 34px 20px; }
section h2 { font-size: clamp(23px, 3.4vw, 32px); margin: 0 0 18px; }

.stats ul {
  list-style: none; margin: 0; padding: 0;
  display: grid; grid-template-columns: repeat(2, 1fr); gap: 12px;
}
@media (min-width: 700px) { .stats ul { grid-template-columns: repeat(4, 1fr); } }
.stats li {
  background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 18px; text-align: center;
}
.stats strong { display: block; font-size: 30px; color: var(--accent); }
.stats span { color: var(--ink-dim); font-size: 14px; }

.grid { display: grid; gap: 16px; grid-template-columns: 1fr; }
@media (min-width: 760px) { .grid { grid-template-columns: 1fr 1fr; } }
.card {
  background: var(--panel); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 22px;
}
.card h3 { margin: 0 0 8px; font-size: 18px; }
.card p { margin: 0; color: var(--ink-dim); font-size: 15px; }

.setup { border-top: 1px solid var(--line); }
.steps { counter-reset: step; list-style: none; margin: 8px 0 0; padding: 0; }
.steps li {
  counter-increment: step; position: relative;
  padding: 0 0 20px 46px; border-inline-start: 2px solid var(--line);
  margin-inline-start: 13px;
}
.steps li:last-child { border-inline-start-color: transparent; padding-bottom: 0; }
.steps li::before {
  content: counter(step);
  position: absolute; inset-inline-start: -15px; top: 0;
  width: 28px; height: 28px; border-radius: 50%;
  display: grid; place-items: center;
  background: var(--accent); color: var(--btn-ink);
  font-size: 14px; font-weight: 700;
}
.steps strong { display: block; }
.steps span { color: var(--ink-dim); font-size: 15px; }
.note { color: var(--ink-dim); font-size: 14px; }

.privacy, .pricing { border-top: 1px solid var(--line); }
.privacy p, .pricing p { color: var(--ink-dim); max-width: 72ch; }

.faq { border-top: 1px solid var(--line); }
.faq details {
  background: var(--panel); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 14px 18px; margin-bottom: 10px;
}
.faq summary { cursor: pointer; font-weight: 600; }
.faq p { color: var(--ink-dim); margin: 10px 0 0; }

/* ---------------------------------------------------------- guides
   Additive only: these classes exist solely on /guides/ and the long-tail
   pages, so nothing above changes on the home pages. */

.guide {
  max-width: var(--maxw); margin: 0 auto; padding: 28px 20px 8px;
}
.guide h1 { margin: 8px 0 14px; font-size: clamp(26px, 4.2vw, 40px); }
.guide h2 { margin: 34px 0 12px; font-size: 22px; }
.guide h3 { margin: 24px 0 8px; font-size: 18px; }
.guide p { color: var(--ink-dim); max-width: 72ch; line-height: 1.65; }
.guide ul, .guide ol { color: var(--ink-dim); max-width: 72ch; line-height: 1.65; }
.guide li { margin-bottom: 8px; }
.guide .faq, .guide .pricing { border-top: none; padding: 0; }
.crumbs { font-size: 14px; color: var(--ink-dim); }
.guide-index { list-style: none; margin: 0; padding: 0; }
.guide-index li { margin-bottom: 22px; }
.guide-index h2 { margin: 0 0 6px; font-size: 19px; }
.guide-index p { margin: 0; font-size: 15px; }
.related { list-style: none; margin: 0 0 18px; padding: 0; }

/* ---------------------------------------------------------- footer */

.footer {
  max-width: var(--maxw); margin: 0 auto; padding: 28px 20px 56px;
  border-top: 1px solid var(--line);
}
.langs ul {
  list-style: none; display: flex; flex-wrap: wrap; gap: 8px 16px;
  margin: 0 0 16px; padding: 0; font-size: 15px;
}
.lang-current { color: var(--ink); font-weight: 700; }
.legal { display: flex; flex-wrap: wrap; gap: 8px 18px; font-size: 14px; margin-bottom: 12px; }
.small { color: var(--ink-dim); font-size: 13px; margin: 0; }