/* Chapter-site primitives. Styled after evjang.com/autogo:
   warm cream paper, Fraunces serif at weight 400, JetBrains Mono eyebrows,
   dual OKLCH accents (blue/net + orange/search).

   Generated pages must compose with these classes — no .card. Vocabulary:
     .pc-prose            prose container (typography baseline)
     .pc-eyebrow          mono uppercase label (used for section eyebrows,
                          figure labels, callout titles, skip reasons)
     .pc-figure           figure block (image + caption)
     .pc-figure--zoom     opt-in to click-to-enlarge
     .pc-fig-interactive  host element for JS/SVG figures
     .pc-callout          aside / definition / note
     .pc-callout--alt     orange accent variant (use sparingly)
     .pc-skip             collapsible low-importance block
     .pc-nav              chapter table of contents (in-site nav)
     .pc-page             a single concept page wrapper
*/

@import url('https://fonts.googleapis.com/css2?family=Fraunces:ital,opsz,wght@0,9..144,400;0,9..144,500;0,9..144,600;1,9..144,400&family=JetBrains+Mono:wght@400;500;600&display=swap');

/* Agent compatibility shim — section-writers frequently emit invalid
   SVG like `<rect fill="var(--accent-soft)" />`. SVG presentation
   attributes don't parse `var(...)`, so without this they'd render as
   solid black. CSS attribute selectors match the literal attribute
   string, and CSS — unlike SVG attrs — DOES resolve var(). The brief
   tells agents to use `style="..."` instead, but this safety net keeps
   chapters from looking broken when they slip up. */
svg [fill="var(--accent)"]      { fill: var(--accent); }
svg [fill="var(--accent-alt)"]  { fill: var(--accent-alt); }
svg [fill="var(--accent-soft)"] { fill: var(--accent-soft); }
svg [fill="var(--ink)"]         { fill: var(--ink); }
svg [fill="var(--ink-soft)"]    { fill: var(--ink-soft); }
svg [fill="var(--paper)"]       { fill: var(--paper); }
svg [fill="var(--border)"]      { fill: var(--border); }
svg [fill="var(--bg)"]          { fill: var(--bg); }
svg [stroke="var(--accent)"]      { stroke: var(--accent); }
svg [stroke="var(--accent-alt)"]  { stroke: var(--accent-alt); }
svg [stroke="var(--accent-soft)"] { stroke: var(--accent-soft); }
svg [stroke="var(--ink)"]         { stroke: var(--ink); }
svg [stroke="var(--ink-soft)"]    { stroke: var(--ink-soft); }
svg [stroke="var(--paper)"]       { stroke: var(--paper); }
svg [stroke="var(--border)"]      { stroke: var(--border); }
svg [stroke="var(--bg)"]          { stroke: var(--bg); }
svg [font-family="var(--mono)"]   { font-family: var(--mono); }
svg [font-family="var(--serif)"]  { font-family: var(--serif); }
svg [font-family="var(--sans)"]   { font-family: var(--sans); }

:root {
  --bg: #f6f1e7;
  --bg-soft: #eee6d4;
  --paper: #fbf6ea;
  --ink: #1f1a14;
  --ink-soft: #6a5d4a;
  --border: #d9cdb0;
  /* Dual accent palette: blue for primary callouts / nav, orange for
     contrasts ("alt" callouts, interactive figures, warnings). */
  --accent: oklch(58% 0.12 245);
  --accent-soft: oklch(92% 0.04 245);
  --accent-alt: oklch(55% 0.16 35);
  --accent-alt-soft: oklch(95% 0.04 35);

  --serif: 'Fraunces', Georgia, "Iowan Old Style", serif;
  --mono: 'JetBrains Mono', ui-monospace, SFMono-Regular, Menlo, monospace;
}

* { box-sizing: border-box; }
[hidden] { display: none !important; }

html, body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font: 17px/1.65 var(--serif);
  font-variation-settings: "opsz" 14;
}

/* Body gets the sidebar gutter so prose can re-center via auto margins
   instead of being pinned to the left edge of the post-sidebar area. */
body { padding-left: 200px; }
@media (max-width: 800px) {
  body { padding-left: 0; }
}
.pc-page {
  max-width: 760px;
  margin: 0 auto;
  padding: 64px 32px 96px;
}

/* --- Eyebrow utility ------------------------------------------------ */
/* The autogo signature: mono uppercase label used above sections and
   inside callouts/skip blocks. */
.pc-eyebrow {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  font-weight: 500;
  color: var(--ink-soft);
}

/* Source-page citation for each section. Same monospace family as
   eyebrows but smaller and dimmer — reads as a citation. Clickable:
   when the chapter site is loaded inside paperchat, clicking jumps
   the underlying PDF viewer to that page and closes the chapter
   overlay. The pc.js click handler dispatches a postMessage. */
.pc-source {
  display: inline-block;
  font-family: var(--mono);
  font-size: 10px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--muted, var(--ink-soft));
  opacity: 0.75;
  margin-top: -0.15rem;
  cursor: pointer;
  border: 0;
  background: transparent;
  padding: 2px 6px;
  border-radius: 3px;
  transition: opacity 0.12s ease, background 0.12s ease;
}
.pc-source::before { content: "↳ "; opacity: 0.6; }
.pc-source:hover {
  opacity: 1;
  background: var(--accent-soft);
  color: var(--accent);
}
.pc-source:hover::after {
  content: " — open in PDF";
  opacity: 0.7;
  font-size: 9px;
  letter-spacing: 0.08em;
}

/* --- pc-anki: Anki-style review-card deck ------------------------- */
.pc-anki { margin: 1.4em 0; }
.pc-anki-head {
  display: flex; align-items: baseline; justify-content: space-between;
  gap: 12px; margin-bottom: .5rem;
}
.pc-anki-toggle {
  appearance: none; border: 0; background: transparent; cursor: pointer;
  font-family: var(--mono); font-size: 11px; letter-spacing: 0.12em;
  text-transform: uppercase; color: var(--accent);
  padding: 4px 8px; border-radius: 3px;
}
.pc-anki-toggle:hover { background: var(--accent-soft); }
.pc-anki-list {
  list-style: none; margin: 0; padding: 0;
  border-top: 1px solid var(--border);
}
.pc-anki-card {
  border-bottom: 1px solid var(--border);
}
.pc-anki-q {
  appearance: none; width: 100%; cursor: pointer;
  display: flex; align-items: flex-start; gap: 14px;
  padding: 14px 10px; text-align: left;
  background: transparent; border: 0;
  font: inherit; color: var(--ink);
  line-height: 1.45;
  transition: background 0.12s ease;
}
.pc-anki-q:hover { background: var(--accent-soft); }
.pc-anki-num {
  font-family: var(--mono); font-size: 11px; font-weight: 500;
  color: var(--muted); flex: 0 0 28px; padding-top: 2px;
  font-variant-numeric: tabular-nums;
}
.pc-anki-q-text { flex: 1; }
.pc-anki-chev {
  flex: 0 0 16px; color: var(--accent); font-size: 12px;
  transition: transform 0.18s ease; padding-top: 2px;
}
.pc-anki-open .pc-anki-chev { transform: rotate(90deg); }
.pc-anki-a {
  padding: 0 10px 14px 52px;  /* aligned with the question text (gap+num) */
}
.pc-anki-a-inner {
  border-left: 2px solid var(--accent);
  padding: 4px 14px;
  color: var(--ink-soft);
  font-size: 15px;
  line-height: 1.55;
}
.pc-anki-a-inner p:first-child { margin-top: 0; }
.pc-anki-a-inner p:last-child  { margin-bottom: 0; }

/* --- pc-term: inline term with hover/focus tooltip ---------------- */
.pc-term {
  position: relative;
  display: inline;
  cursor: help;
  outline: none;
}
.pc-term-trigger {
  border-bottom: 1px dashed var(--accent);
  padding-bottom: 1px;
}
.pc-term:hover .pc-term-trigger,
.pc-term:focus .pc-term-trigger,
.pc-term.pc-term-open .pc-term-trigger {
  background: var(--accent-soft);
}
/* Tooltip is rendered as a popover so it always paints in the browser's
   top layer, escaping any ancestor stacking context created by
   pc-rise / pc-fade-in transforms. JS positions it relative to the trigger. */
.pc-term-tip {
  position: fixed;
  inset: auto;
  margin: 0;
  border: 0;
  width: max-content;
  max-width: min(360px, 80vw);
  padding: 10px 12px;
  background: var(--ink);
  color: var(--paper);
  font-family: var(--serif);
  font-size: 13px;
  line-height: 1.45;
  letter-spacing: 0;
  text-transform: none;
  border-radius: 4px;
  box-shadow: 0 6px 18px rgba(0,0,0,0.18);
  white-space: normal;
  overflow: visible;
}
.pc-term-tip:not(:popover-open) { display: none; }
.pc-term-tip::before {
  content: "";
  position: absolute;
  left: 14px;
  top: -5px;
  width: 10px; height: 10px;
  background: var(--ink);
  transform: rotate(45deg);
}

/* --- Prose ---------------------------------------------------------- */
.pc-prose h1,
.pc-prose h2,
.pc-prose h3 {
  font-family: var(--serif);
  font-weight: 400;
  letter-spacing: -0.012em;
  font-variation-settings: "opsz" 96;
  color: var(--ink);
}
.pc-prose h1 { font-size: 2.4rem; line-height: 1.15; margin: 0 0 0.4em; }
.pc-prose h2 { font-size: 1.55rem; line-height: 1.2; margin: 2.2em 0 0.5em; }
.pc-prose h3 {
  font-size: 1.0rem;
  line-height: 1.3;
  margin: 1.6em 0 0.3em;
  color: var(--ink-soft);
  font-family: var(--mono);
  font-weight: 500;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}
.pc-prose p  { margin: 0 0 1em; }
.pc-prose em { font-style: italic; }
.pc-prose strong { font-weight: 600; }
.pc-prose a  {
  color: var(--accent);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
  text-decoration-color: color-mix(in srgb, var(--accent) 50%, transparent);
}
.pc-prose a:hover { text-decoration-color: var(--accent); }
.pc-prose code {
  font: 0.9em/1.4 var(--mono);
  background: var(--bg-soft);
  padding: 0.05em 0.4em;
  border-radius: 3px;
  color: var(--ink);
}
.pc-prose pre {
  background: #1f1a14;
  color: #f6f1e7;
  padding: 14px 16px;
  border-radius: 6px;
  overflow-x: auto;
  font: 0.88em/1.55 var(--mono);
}
.pc-prose pre code { background: none; color: inherit; padding: 0; }
.pc-prose blockquote {
  margin: 1em 0;
  padding: 0.1em 0 0.1em 16px;
  border-left: 2px solid var(--accent);
  color: var(--ink-soft);
  font-style: italic;
}

/* sub/sup compressed like autogo */
.pc-prose sub, .pc-prose sup { font-size: 0.7em; }

/* --- Figures -------------------------------------------------------- */
.pc-figure {
  margin: 1.8em 0;
  text-align: center;
}
.pc-figure img,
.pc-figure svg,
.pc-figure canvas {
  max-width: 100%;
  height: auto;
  background: var(--paper);
  border: 1px solid var(--border);
  border-radius: 3px;
}
.pc-figure figcaption {
  margin-top: 0.7em;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.06em;
  color: var(--ink-soft);
}
.pc-figure figcaption strong {
  text-transform: uppercase;
  letter-spacing: 0.22em;
  color: var(--ink);
  margin-right: 0.5em;
  font-weight: 500;
}
.pc-figure--zoom img { cursor: zoom-in; }

.pc-fig-interactive {
  background: var(--paper);
  border: 1px solid var(--border);
  border-radius: 3px;
  padding: 16px;
  margin: 1.8em 0;
}

/* --- Callouts ------------------------------------------------------- */
.pc-callout {
  margin: 1.4em 0;
  padding: 14px 18px;
  background: var(--accent-soft);
  border-left: 2px solid var(--accent);
  border-radius: 0 4px 4px 0;
}
.pc-callout > :first-child { margin-top: 0; }
.pc-callout > :last-child  { margin-bottom: 0; }
.pc-callout-title {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  font-weight: 500;
  color: var(--accent);
  margin-bottom: 0.4em;
}
.pc-callout--alt {
  background: var(--accent-alt-soft);
  border-left-color: var(--accent-alt);
}
.pc-callout--alt .pc-callout-title { color: var(--accent-alt); }

/* --- Skip blocks ---------------------------------------------------- */
.pc-skip {
  margin: 1.4em 0;
  padding: 8px 14px;
  border: 1px dashed var(--border);
  border-radius: 4px;
  background: transparent;
  color: var(--ink-soft);
}
.pc-skip > summary {
  cursor: pointer;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.12em;
  color: var(--ink-soft);
  list-style: none;
  padding: 4px 0;
}
.pc-skip > summary::before {
  content: "▸ ";
  color: var(--accent);
}
.pc-skip[open] > summary::before { content: "▾ "; }
.pc-skip[open] {
  background: var(--paper);
  color: var(--ink);
  padding-bottom: 12px;
}
.pc-skip-reason {
  font-family: var(--mono);
  font-size: 10px;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--accent);
  margin-right: 0.5em;
}
body.pc-skip-hide .pc-skip { display: none; }

/* --- Left-side sticky section nav (autogo SectionSidebar idiom) ------
   The chapter site is infinite-scroll: all .pc-page sections stacked
   vertically. This nav is a fixed strip on the left that auto-highlights
   the active section as the user scrolls. */
.pc-nav {
  position: fixed;
  left: 16px;
  top: 24px;
  bottom: 24px;
  width: 168px;
  display: flex;
  flex-direction: column;
  gap: 6px;
  font-family: var(--mono);
  font-size: 12px;
  color: var(--ink-soft);
  z-index: 10;
  overflow-y: auto;
}
@media (max-width: 800px) {
  .pc-nav { position: static; flex-direction: row; flex-wrap: wrap; width: auto; padding: 12px 16px; border-bottom: 1px solid var(--border); }
}

.pc-nav .pc-nav-title {
  font-size: 11px;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  font-weight: 500;
  color: var(--ink-soft);
  padding: 4px 8px 8px;
  border-bottom: 1px dotted var(--border);
  margin-bottom: 4px;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.pc-nav .pc-nav-pages { display: flex; flex-direction: column; gap: 2px; }
.pc-nav a {
  display: block;
  font-size: 12px;
  letter-spacing: 0.04em;
  color: var(--ink);
  text-decoration: none;
  padding: 4px 8px;
  border-left: 2px solid transparent;
  border-radius: 0;
  opacity: 0.6;
  transition: all 70ms ease-out;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.pc-nav a:hover { background: rgba(31, 26, 20, 0.06); opacity: 1; }
.pc-nav a.pc-done    { opacity: 0.5; }
.pc-nav a[aria-current="page"] {
  background: var(--ink);
  color: var(--bg);
  opacity: 1;
  border-left-color: var(--accent);
  font-weight: 600;
}
.pc-nav .pc-skip-toggle {
  font-family: var(--mono);
  font-size: 10px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  border: 1px solid var(--border);
  background: transparent;
  padding: 5px 10px;
  border-radius: 3px;
  cursor: pointer;
  color: var(--ink-soft);
  align-self: flex-start;
  margin-top: 8px;
}
.pc-nav .pc-skip-toggle:hover { background: rgba(31, 26, 20, 0.06); color: var(--ink); }

/* Each section gets a top margin so scrollIntoView places it nicely
   below the optional fixed-top spacing (we don't have a top bar but a
   little breathing room helps when jumping). */
section.pc-page { scroll-margin-top: 24px; min-height: 60vh; }
.pc-nav .pc-skip-toggle[aria-pressed="true"] { background: var(--ink); color: var(--bg); border-color: var(--ink); }

/* --- Anchored headings --------------------------------------------- */
.pc-prose h2,
.pc-prose h3 { position: relative; }
.pc-anchor {
  position: absolute;
  left: -22px;
  top: 0.1em;
  opacity: 0;
  transition: opacity 0.1s;
  color: var(--ink-soft);
  text-decoration: none;
  font-weight: normal;
}
.pc-prose h2:hover .pc-anchor,
.pc-prose h3:hover .pc-anchor { opacity: 1; }

/* --- Zoom lightbox ------------------------------------------------- */
.pc-zoom-overlay {
  position: fixed;
  inset: 0;
  background: rgba(10, 8, 4, 0.88);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  cursor: zoom-out;
}
.pc-zoom-overlay img {
  max-width: 95vw;
  max-height: 95vh;
  background: var(--paper);
  box-shadow: 0 8px 40px rgba(0, 0, 0, 0.4);
}

/* KaTeX defense-in-depth */
.katex .katex-mathml {
  position: absolute !important;
  clip: rect(1px, 1px, 1px, 1px) !important;
  width: 1px !important;
  height: 1px !important;
  overflow: hidden !important;
}
.katex-display { overflow-x: auto; overflow-y: hidden; }

/* Visible focus indicator (autogo-style). */
:focus-visible {
  outline: 2px solid var(--ink);
  outline-offset: 2px;
  border-radius: 2px;
}
:focus:not(:focus-visible) { outline: none; }

/* --- Animation primitives (autogo-style) ---------------------------- */
/* Defaults: 70ms ease-out (autogo's transition baseline). Entrance
   animations are subtle — small Y shift + opacity. Honor reduced-motion. */

@keyframes pcFadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to   { opacity: 1; transform: translateY(0); }
}
@keyframes pcRise {
  from { opacity: 0; transform: translateY(16px); }
  to   { opacity: 1; transform: translateY(0); }
}
@keyframes pcDrawIn {
  to { stroke-dashoffset: 0; }
}

/* Apply to any element to fade-up when it enters the viewport (wired by
   pc.js IntersectionObserver). Initial state is transparent; the
   .pc-revealed class flipped by pc.js plays the animation. */
.pc-fade-in {
  opacity: 0;
  transform: translateY(8px);
  will-change: opacity, transform;
}
.pc-fade-in.pc-revealed {
  animation: pcFadeIn 180ms cubic-bezier(0.2, 0.7, 0.2, 1) forwards;
}
.pc-rise {
  opacity: 0;
  transform: translateY(16px);
  will-change: opacity, transform;
}
.pc-rise.pc-revealed {
  animation: pcRise 240ms cubic-bezier(0.2, 0.7, 0.2, 1) forwards;
}

/* Stagger children: each child gets a sequential delay (40ms steps).
   Up to 16 children — autogo never needs more in one batch. */
.pc-stagger > .pc-fade-in,
.pc-stagger > .pc-rise {
  animation-delay: calc(var(--pc-i, 0) * 40ms);
}

/* SVG path that draws itself in: pc.js measures path length and sets
   stroke-dasharray; the .pc-revealed class plays pcDrawIn. */
.pc-draw {
  stroke-dasharray: var(--pc-len, 1000);
  stroke-dashoffset: var(--pc-len, 1000);
}
.pc-draw.pc-revealed {
  animation: pcDrawIn 600ms cubic-bezier(0.2, 0.7, 0.2, 1) forwards;
}

/* Page transitions (hash-routed): fade-out the leaving page, fade-up the
   entering one. Default transition is autogo's 140ms baseline. */
section.pc-page {
  transition: opacity 70ms ease-out;
}
section.pc-page.pc-leaving {
  opacity: 0;
  pointer-events: none;
}
section.pc-page.pc-entering {
  animation: pcFadeIn 160ms cubic-bezier(0.2, 0.7, 0.2, 1);
}

/* Smooth color / state transitions on interactive bits. */
.pc-callout, .pc-figure, .pc-fig-interactive, .pc-skip,
.pc-nav a, .pc-nav .pc-skip-toggle {
  transition: background 70ms ease-out, color 70ms ease-out, border-color 70ms ease-out;
}

/* Reduced-motion: kill everything, snap to final state. */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
    scroll-behavior: auto !important;
  }
  .pc-fade-in, .pc-rise { opacity: 1; transform: none; }
  .pc-draw { stroke-dashoffset: 0 !important; }
}