/* chapter.css — Chapter-specific typography and structural styling.
 * Uses tokens from tokens.css and the .prose wrapper from layout.css.
 */

/* ===== Chapter header ===== */
.chapter-header {
  margin-bottom: var(--space-8);
  border-bottom: 1px solid var(--color-border);
  padding-bottom: var(--space-6);
}
.chapter-header h1 {
  margin-top: var(--space-2);
  margin-bottom: var(--space-3);
}
.chapter-description {
  font-size: var(--text-lg);
  color: var(--color-text-muted);
  margin: var(--space-3) 0;
  text-indent: 0;
  font-style: italic;
}
.chapter-meta {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-4);
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  font-family: var(--font-code);
  margin-bottom: var(--space-2);
}
.chapter-meta > span {
  display: inline-flex;
  gap: 0.3em;
}
.chapter-meta-label {
  text-transform: uppercase;
  letter-spacing: 0.05em;
  font-size: 0.75em;
}

/* Inline companion-artifact chips inside .chapter-meta.
 * v3.2.0: structural inline rendering. Previous v3.1.0 emitted a sibling
 * <aside class="chapter-companions"><ul>...</ul></aside> with no CSS
 * coverage; UA-default block layout added ~100px height at <=1280px,
 * producing a uniform vertical pixel shift on academic chapter pages
 * vs the v2.0 baseline. The inline span here adds zero block height by
 * construction; styling matches the surrounding .chapter-meta spans. */
.chapter-companion {
  font-family: var(--font-code);
  font-size: var(--text-sm);
  color: var(--color-text-muted);
}
.chapter-companion a,
.chapter-companion code {
  color: inherit;
  text-decoration: none;
  border-bottom: 1px dotted var(--color-border);
}
.chapter-companion a:hover {
  color: var(--color-link);
  border-bottom-style: solid;
}

/* Volatility + tool badges: reuse .tool-badge from callouts.css */
.volatility-badge {
  display: inline-block;
  padding: 0.05em 0.45em;
  border-radius: var(--radius-sm);
  font-size: var(--text-xs);
  font-weight: 500;
  font-family: var(--font-code);
  letter-spacing: 0;
}
.volatility-stable-principle {
  background: var(--warm-green-tint);
  color: var(--warm-green);
  border: 1px solid var(--warm-green);
}
.volatility-architectural-pattern {
  background: var(--warm-gold-tint);
  color: var(--warm-gold);
  border: 1px solid var(--warm-gold);
}
.volatility-feature-surface {
  background: var(--warm-rose-tint);
  color: var(--warm-rose);
  border: 1px solid var(--warm-rose);
}

/* Freshness badge — inline with "Last verified" in chapter-meta.
 * Three status bands map to the same warm palette as volatility:
 *   fresh       → green  (last_verified is recent relative to volatility threshold)
 *   verify-soon → gold   (75-100% of threshold elapsed)
 *   stale       → rose   (past threshold; verify before trusting claims)
 */
.freshness-badge {
  display: inline-block;
  padding: 0.02em 0.45em;
  border-radius: var(--radius-sm);
  font-size: 0.85em;
  font-weight: 500;
  letter-spacing: 0;
  line-height: 1.4;
  vertical-align: baseline;
  cursor: help;
  /* Prevent the "2026-04-17 · Fresh" pair from breaking across lines when
   * chapter-meta wraps on narrow viewports. */
  white-space: nowrap;
}
.freshness-badge[data-status='fresh'] {
  background: var(--warm-green-tint);
  color: var(--warm-green);
  border: 1px solid var(--warm-green);
}
.freshness-badge[data-status='verify-soon'] {
  background: var(--warm-gold-tint);
  color: var(--warm-gold);
  border: 1px solid var(--warm-gold);
}
.freshness-badge[data-status='stale'] {
  background: var(--warm-rose-tint);
  color: var(--warm-rose);
  border: 1px solid var(--warm-rose);
  font-weight: 600;
}

.chapter-badge-row {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  align-items: center;
  margin-top: var(--space-3);
  font-size: var(--text-sm);
  color: var(--color-text-muted);
}
.chapter-badge-row-label {
  font-weight: 500;
}

/* ===== Chapter TOC (collapsed <details> at top) ===== */
.chapter-toc {
  margin: var(--space-4) 0 var(--space-6);
  padding: var(--space-2) var(--space-3);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background: var(--color-bg-subtle);
  font-size: var(--text-sm);
}
.chapter-toc > summary {
  cursor: pointer;
  font-weight: 500;
  color: var(--color-link);
  list-style: none;
  padding: var(--space-1) 0;
}
.chapter-toc > summary::-webkit-details-marker {
  display: none;
}
.chapter-toc > summary::before {
  content: "▸ ";
  display: inline-block;
  transition: transform 120ms ease;
}
.chapter-toc[open] > summary::before {
  content: "▾ ";
}
.chapter-toc ol {
  list-style: none;
  padding-left: 0;
  margin: var(--space-2) 0 0;
}
.chapter-toc li {
  margin: var(--space-1) 0;
  padding-left: var(--space-3);
  border-left: 2px solid var(--color-border);
}
.chapter-toc li.toc-h3 {
  padding-left: var(--space-6);
}
.chapter-toc a {
  text-decoration: none;
  color: var(--color-text);
}
.chapter-toc a:hover {
  text-decoration: underline;
  color: var(--color-link);
}

/* ===== Chapter nav (prev/next at bottom) ===== */
.chapter-nav {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-4);
  margin-top: var(--space-12);
  padding-top: var(--space-6);
  border-top: 1px solid var(--color-border);
}
.chapter-nav a {
  display: block;
  padding: var(--space-3);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  text-decoration: none;
  color: var(--color-text);
  transition: border-color 120ms ease, background 120ms ease;
}
.chapter-nav a:hover {
  border-color: var(--color-link);
  background: var(--color-bg-subtle);
}
.chapter-nav a .nav-label {
  display: block;
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 0.25em;
}
.chapter-nav a .nav-title {
  font-weight: 500;
  color: var(--color-link);
}
.chapter-nav .prev { text-align: left; }
.chapter-nav .next { text-align: right; grid-column: 2; }
.chapter-nav .prev:only-child { grid-column: 1; }

@media (max-width: 48rem) {
  .chapter-nav {
    grid-template-columns: 1fr;
  }
  .chapter-nav .next { grid-column: 1; text-align: left; }
}

/* Display math (KaTeX) — scroll a too-wide equation WITHIN its own block instead
   of forcing a horizontal scroll on the whole page. KaTeX sets no `overflow` on
   `.katex-display`, so it defaults to `visible`; a wide equation (long
   derivations, big matrices) then overflows the viewport and the page scrolls
   sideways on mobile. WCAG 1.4.10 Reflow. See book-scaffold-astro#162.
   overflow-y is deliberately NOT set: once overflow-x is non-visible the CSS
   overflow rule already computes overflow-y to `auto`, so there is no spurious
   vertical scrollbar — and an explicit `hidden` would silently clip tall
   equations if a consumer ever constrains .katex-display's height. */
.katex-display {
  overflow-x: auto;
  /* a little room so the horizontal scrollbar doesn't clip the equation's descenders */
  padding-block-end: 0.25rem;
  /* Edge scroll-shadow when a wide equation scrolls (v4.25.3; docs/responsive-reading.md).
   * Same Lea Verou layered technique as code blocks, page-bg covers. */
  background-image:
    linear-gradient(to right, var(--color-bg) 30%, rgba(0, 0, 0, 0)),
    linear-gradient(to right, rgba(0, 0, 0, 0), var(--color-bg) 70%),
    radial-gradient(farthest-side at 0 50%, rgba(0, 0, 0, 0.12), rgba(0, 0, 0, 0)),
    radial-gradient(farthest-side at 100% 50%, rgba(0, 0, 0, 0.12), rgba(0, 0, 0, 0));
  background-position: 0 0, 100% 0, 0 0, 100% 0;
  background-repeat: no-repeat;
  background-size: 30px 100%, 30px 100%, 12px 100%, 12px 100%;
  background-attachment: local, local, scroll, scroll;
}