/* Per-problem page layout */

.page-hero {
  padding: 48px 0 28px;
  border-bottom: 1px solid var(--hairline);
}
.page-hero .eyebrow { display: block; margin-bottom: 14px; }
.page-hero h1 {
  font-size: clamp(40px, 6vw, 72px);
  letter-spacing: -0.02em;
  line-height: 1.02;
  max-width: 18ch;
}
.page-hero .standfirst {
  margin-top: 18px;
  font-family: var(--font-display);
  font-style: italic;
  font-size: clamp(17px, 1.6vw, 21px);
  line-height: 1.45;
  color: var(--muted);
  max-width: 56ch;
}
.page-hero .hero-meta {
  margin-top: 22px;
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

/* Two-column article grid */
.article {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1.6fr);
  gap: clamp(28px, 4vw, 64px);
  padding: 48px 0;
}
.article .col-aside { min-width: 0; }
.article .col-main  { min-width: 0; }

@media (max-width: 920px) {
  .article { grid-template-columns: 1fr; }
}

.section {
  padding: 32px 0;
  border-top: 1px solid var(--hairline);
}
.section:first-of-type { border-top: 0; }

.section-title {
  font-family: var(--font-display);
  font-size: clamp(22px, 2.4vw, 30px);
  letter-spacing: -0.01em;
  margin-bottom: 14px;
}
.section-title .num {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.18em;
  color: var(--accent);
  display: block;
  margin-bottom: 6px;
  text-transform: uppercase;
}

.lede {
  font-family: var(--font-display);
  font-size: clamp(18px, 1.8vw, 22px);
  line-height: 1.5;
  max-width: 60ch;
}
.body-prose { max-width: 62ch; }
.body-prose p { margin: 0 0 14px; }
.body-prose p:last-child { margin-bottom: 0; }
.body-prose strong { font-weight: 600; }
.body-prose code {
  font-family: var(--font-mono);
  font-size: 0.92em;
  background: var(--ink-soft);
  padding: 1px 4px;
  border-radius: 2px;
}

/* Spec table */
.spec-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 13px;
  font-variant-numeric: tabular-nums;
}
.spec-table th,
.spec-table td {
  text-align: left;
  padding: 9px 0;
  border-bottom: 1px solid var(--hairline);
  vertical-align: top;
}
.spec-table th {
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: 0.10em;
  text-transform: uppercase;
  color: var(--muted);
  font-weight: 500;
  width: 44%;
}
.spec-table td {
  color: var(--fg);
  font-family: var(--font-mono);
}
.spec-table .pass { color: var(--accent); }

/* I/O specification block */
.io-block {
  display: grid;
  grid-template-columns: 1fr;
  gap: 14px;
}
.io-card {
  border: 1px solid var(--hairline);
  background: var(--surface);
  padding: 14px 16px;
}
.io-card .label {
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 6px;
}
.io-card .sig {
  font-family: var(--font-mono);
  font-size: 12.5px;
  color: var(--fg);
  white-space: pre-wrap;
  word-break: break-word;
}

/* Visualization canvas */
.viz {
  margin-top: 8px;
  border: 1px solid var(--hairline);
  background: var(--surface);
}
.viz-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 14px;
  border-bottom: 1px solid var(--hairline);
  gap: 16px;
  flex-wrap: wrap;
}
.viz-head .caption {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.10em;
  text-transform: uppercase;
  color: var(--muted);
}
.viz-stage {
  position: relative;
  padding: 18px;
  min-height: 320px;
  display: flex;
  align-items: center;
  justify-content: center;
  background:
    repeating-linear-gradient(
      0deg,
      transparent 0 24px,
      var(--ink-soft) 24px 24px
    ),
    var(--surface);
  background:
    radial-gradient(circle at 16px 16px, var(--ink-soft) 1px, transparent 1.5px) 0 0 / 24px 24px,
    var(--surface);
}
.viz-stage svg { width: 100%; height: 100%; display: block; }
.viz-stage .stage-svg { width: 100%; max-width: 720px; }
.viz-foot {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 14px;
  border-top: 1px solid var(--hairline);
  gap: 12px;
  flex-wrap: wrap;
}
.viz-controls {
  display: flex;
  align-items: center;
  gap: 8px;
}
.viz-controls .btn { padding: 6px 12px; font-size: 12px; }
.step-info {
  font-family: var(--font-mono);
  font-size: 11.5px;
  color: var(--muted);
  letter-spacing: 0.04em;
}
.step-info .step-label {
  color: var(--fg);
  font-weight: 500;
}

/* Step narrator */
.step-narrator {
  padding: 14px 16px;
  border-top: 1px solid var(--hairline);
  font-family: var(--font-display);
  font-style: italic;
  font-size: 15px;
  line-height: 1.5;
  color: var(--fg);
  min-height: 56px;
}
.step-narrator .step-tag {
  display: inline-block;
  font-family: var(--font-mono);
  font-style: normal;
  font-size: 10.5px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  margin-right: 8px;
}

/* Algorithm pseudo block */
.pseudo {
  font-family: var(--font-mono);
  font-size: 12.5px;
  line-height: 1.6;
  white-space: pre-wrap;
  background: var(--paper);
  border: 1px solid var(--hairline);
  border-left: 3px solid var(--accent);
  padding: 14px 16px;
  margin: 0;
  overflow-x: auto;
}

/* Pull quote */
.pullquote {
  font-family: var(--font-display);
  font-size: clamp(22px, 2.6vw, 32px);
  font-style: italic;
  line-height: 1.25;
  letter-spacing: -0.01em;
  margin: 28px 0;
  padding: 4px 0 6px 18px;
  border-left: 2px solid var(--accent);
  max-width: 28ch;
}

/* Related problems */
.related {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 14px;
}
.related a {
  display: block;
  border: 1px solid var(--hairline);
  background: var(--surface);
  padding: 12px 14px;
  transition: border-color 100ms ease;
}
.related a:hover { border-color: var(--fg); }
.related .r-eyebrow {
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--accent);
}
.related .r-title {
  display: block;
  font-family: var(--font-display);
  font-size: 17px;
  letter-spacing: -0.01em;
  margin-top: 4px;
}

/* Difficulty meta */
.diff-row { display: flex; gap: 4px; align-items: center; }
.diff-dot {
  width: 8px; height: 8px;
  border: 1px solid var(--rule);
  border-radius: 50%;
  background: transparent;
}
.diff-dot.on { background: var(--accent); border-color: var(--accent); }

/* Back link */
.back-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--muted);
  padding: 10px 0;
}
.back-link:hover { color: var(--accent); }
.back-link::before { content: "←"; font-family: var(--font-display); font-size: 14px; }

/* Stat ribbon */
.stat-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: 0;
  border: 1px solid var(--hairline);
  background: var(--surface);
}
.stat-row .cell {
  padding: 14px 16px;
  border-right: 1px solid var(--hairline);
}
.stat-row .cell:last-child { border-right: 0; }
.stat-row .cell .k {
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--muted);
}
.stat-row .cell .v {
  font-family: var(--font-display);
  font-size: 22px;
  letter-spacing: -0.01em;
  margin-top: 4px;
  display: block;
  font-variant-numeric: tabular-nums;
}

/* small */
.muted { color: var(--muted); }
.serif { font-family: var(--font-display); }
.mono  { font-family: var(--font-mono); }