:root {
  --bg: #f7f5f0;
  --bg-alt: #efece5;
  --panel: #ffffff;
  --ink: #1c1a17;
  --ink-soft: #55504a;
  --ink-faint: #8a837a;
  --line: #ddd7cc;
  --accent: #a4243b;
  --accent-soft: #e8d5d9;
  --serif: "Iowan Old Style", "Palatino Linotype", "Book Antiqua", Palatino, Georgia, serif;
  --sans: "Inter", "Helvetica Neue", Helvetica, Arial, sans-serif;
  --mono: "SF Mono", "Fira Code", Menlo, Consolas, monospace;
  --content-size: 18px;
  --sidebar-w: 300px;
}
html[data-theme="dark"] {
  --bg: #15161a;
  --bg-alt: #1b1d22;
  --panel: #1f2127;
  --ink: #e8e4dc;
  --ink-soft: #b3ada2;
  --ink-faint: #777168;
  --line: #33353d;
  --accent: #e07a8b;
  --accent-soft: #3a2a2f;
}
* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; height: 100%; }
body {
  background: var(--bg);
  color: var(--ink);
  font-family: var(--serif);
  font-size: var(--content-size);
  line-height: 1.62;
}

#app { display: grid; grid-template-rows: auto 1fr; grid-template-columns: var(--sidebar-w) 1fr; height: 100vh; }
#topbar {
  grid-column: 1 / -1;
  display: flex; align-items: center; gap: 14px;
  padding: 10px 18px;
  background: var(--panel);
  border-bottom: 1px solid var(--line);
  z-index: 30;
}
#brand { display: flex; align-items: baseline; gap: 10px; min-width: 0; }
.flp-title { font-family: var(--sans); font-weight: 700; font-size: 15px; letter-spacing: .01em; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.flp-sub { font-family: var(--sans); font-size: 12px; color: var(--ink-faint); }
#menu-toggle { display: none; background: none; border: 1px solid var(--line); border-radius: 6px; color: var(--ink); font-size: 16px; padding: 4px 10px; cursor: pointer; }
#toolbar { margin-left: auto; display: flex; gap: 6px; }
#toolbar button {
  font-family: var(--sans); font-size: 13px; color: var(--ink-soft);
  background: none; border: 1px solid var(--line); border-radius: 6px;
  padding: 4px 10px; cursor: pointer;
}
#toolbar button:hover { color: var(--accent); border-color: var(--accent); }

#sidebar {
  background: var(--bg-alt);
  border-right: 1px solid var(--line);
  overflow: hidden;
  display: flex; flex-direction: column;
}
#sidebar-scroll { overflow-y: auto; padding: 14px 0 40px; }
.sidebar-loading { padding: 20px; font-family: var(--sans); font-size: 13px; color: var(--ink-faint); }

.vol-group { margin-bottom: 6px; }
.vol-head {
  font-family: var(--sans); font-weight: 700; font-size: 12.5px; letter-spacing: .06em;
  text-transform: uppercase; color: var(--ink-faint);
  padding: 12px 18px 6px;
}
.vol-head .vol-desc { display: block; text-transform: none; letter-spacing: 0; font-weight: 400; font-size: 11.5px; margin-top: 2px; }
.toc-item {
  display: flex; gap: 8px; align-items: baseline;
  padding: 4px 18px 4px 18px;
  font-family: var(--sans); font-size: 13px; color: var(--ink-soft);
  cursor: pointer; border: none; background: none; width: 100%; text-align: left;
}
.toc-item:hover { background: var(--accent-soft); color: var(--ink); }
.toc-item.active { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
.toc-item .num { color: var(--ink-faint); font-variant-numeric: tabular-nums; min-width: 26px; }
.toc-item .ttl { flex: 1; }
.toc-item .viz-dot { color: var(--accent); font-size: 10px; visibility: hidden; }
.toc-item.has-viz .viz-dot { visibility: visible; }

#content { overflow-y: auto; position: relative; scroll-behavior: smooth; }
#welcome { max-width: 680px; margin: 0 auto; padding: 80px 32px; }
#welcome h1 { font-size: 34px; line-height: 1.2; margin: 0 0 8px; }
.welcome-sub { color: var(--ink-soft); font-size: 16px; margin: 0 0 28px; }
.welcome-note { color: var(--ink-soft); font-size: 17px; margin: 0 0 40px; }
.welcome-vol { padding: 18px 0; border-top: 1px solid var(--line); }
.welcome-vol h3 { font-family: var(--sans); font-size: 15px; margin: 0 0 4px; }
.welcome-vol p { margin: 0; color: var(--ink-soft); font-size: 15px; }
.welcome-vol a { color: var(--accent); text-decoration: none; font-family: var(--sans); font-size: 14px; }

#chapter { max-width: 760px; margin: 0 auto; padding: 44px 32px 120px; }
.chapter-crumb { font-family: var(--sans); font-size: 12.5px; color: var(--ink-faint); text-transform: uppercase; letter-spacing: .05em; margin-bottom: 10px; }
.chapter-title { font-size: 30px; line-height: 1.22; margin: 0 0 6px; }
.chapter-title .ch-num { color: var(--accent); margin-right: 10px; }
.chapter-photo { margin: 22px 0; }
.chapter-photo img { max-width: 100%; border-radius: 4px; filter: saturate(.92); }
.chapter-photo figcaption { font-family: var(--sans); font-size: 12.5px; color: var(--ink-faint); margin-top: 6px; }

.sec { margin-top: 44px; }
.sec-head { display: flex; gap: 12px; align-items: baseline; margin-bottom: 14px; }
.sec-num { font-family: var(--sans); font-weight: 700; color: var(--accent); font-size: 15px; white-space: nowrap; }
.sec-title { font-size: 21px; margin: 0; line-height: 1.3; }

p.p { margin: 0 0 14px; }
p.p em { font-style: italic; }

.eq { margin: 20px 0; overflow-x: auto; overflow-y: hidden; padding: 2px 4px; }
.eq .eq-tag { font-family: var(--sans); font-size: 12px; color: var(--ink-faint); margin-left: 18px; white-space: nowrap; }
.eq .katex-display { margin: 0; }

.fig { margin: 26px 0; }
.fig img { max-width: 100%; display: block; border-radius: 3px; }
html[data-theme="dark"] .fig img { filter: invert(.92) hue-rotate(180deg); }
.fig .cap { font-size: 14.5px; color: var(--ink-soft); margin-top: 8px; }
.fig .cap .tag { font-weight: 700; font-family: var(--sans); font-size: 13px; margin-right: 6px; }
.fig-multi { display: flex; flex-wrap: wrap; gap: 10px; }
.fig-multi img { flex: 1 1 180px; max-width: 100%; }
.fig-multi .cap { flex-basis: 100%; }

.table-block { margin: 26px 0; overflow-x: auto; }
.table-block table { border-collapse: collapse; font-size: 15.5px; }
.table-block td, .table-block th { padding: 5px 12px; border-bottom: 1px solid var(--line); vertical-align: top; }
.table-block .cap { font-size: 14.5px; color: var(--ink-soft); margin-top: 8px; }
.table-block .cap .tag { font-weight: 700; font-family: var(--sans); font-size: 13px; margin-right: 6px; }

.note { margin: 20px 0; padding: 10px 16px; border-left: 3px solid var(--accent); background: var(--bg-alt); font-size: 15.5px; color: var(--ink-soft); }

.footnotes { margin-top: 60px; border-top: 1px solid var(--line); padding-top: 18px; font-size: 14.5px; color: var(--ink-soft); }
.footnotes h4 { font-family: var(--sans); font-size: 12.5px; text-transform: uppercase; letter-spacing: .06em; margin: 0 0 10px; color: var(--ink-faint); }
.footnotes ol { margin: 0; padding-left: 22px; }
.footnotes li { margin-bottom: 8px; }

.viz-card {
  margin: 34px 0; border: 1px solid var(--line); border-radius: 10px;
  background: var(--panel); overflow: hidden;
}
.viz-head {
  display: flex; align-items: center; gap: 10px;
  padding: 12px 18px; border-bottom: 1px solid var(--line);
  font-family: var(--sans); font-size: 13px; font-weight: 700; letter-spacing: .02em;
  text-transform: uppercase; color: var(--accent);
}
.viz-head .viz-kind { margin-left: auto; text-transform: none; letter-spacing: 0; font-weight: 400; color: var(--ink-faint); font-size: 12px; }
.viz-body { padding: 16px 18px 20px; }
.viz-body canvas { max-width: 100%; height: auto; display: block; margin: 0 auto; }
.viz-legend { display: flex; flex-wrap: wrap; gap: 16px; margin-top: 12px; font-family: var(--sans); font-size: 12.5px; color: var(--ink-soft); }
.viz-legend .lg { display: flex; align-items: center; gap: 6px; }
.viz-legend .sw { width: 12px; height: 12px; border-radius: 3px; display: inline-block; }
.viz-controls { display: flex; flex-wrap: wrap; gap: 14px 22px; margin-top: 14px; align-items: center; font-family: var(--sans); font-size: 12.5px; color: var(--ink-soft); }
.viz-controls label { display: flex; align-items: center; gap: 8px; }
.viz-body > label { display: flex; align-items: center; flex-wrap: wrap; gap: 8px; margin-top: 10px; font-family: var(--sans); font-size: 12.5px; color: var(--ink-soft); }
.viz-controls input[type=range] { width: 150px; accent-color: var(--accent); }
.viz-body > label input[type=range] { width: 150px; accent-color: var(--accent); }
.viz-controls .val { font-variant-numeric: tabular-nums; color: var(--ink); min-width: 52px; }
.viz-body > label .val { font-variant-numeric: tabular-nums; color: var(--ink); min-width: 52px; }
.viz-caption { margin-top: 12px; font-size: 14px; color: var(--ink-soft); }

.ch-nav { display: flex; justify-content: space-between; gap: 16px; margin-top: 70px; padding-top: 20px; border-top: 1px solid var(--line); font-family: var(--sans); font-size: 13.5px; }
.ch-nav a { color: var(--accent); text-decoration: none; }
.ch-nav a:hover { text-decoration: underline; }
.ch-nav .disabled { color: var(--ink-faint); }

#scrim { position: fixed; inset: 0; background: rgba(0,0,0,.35); z-index: 20; }

@media (max-width: 900px) {
  #app { grid-template-columns: minmax(0, 1fr); }
  #topbar { padding: 8px 12px; gap: 10px; min-width: 0; }
  #brand { flex: 1 1 auto; min-width: 0; }
  .flp-sub { display: none; }
  #toolbar { flex: 0 0 auto; }
  #sidebar { position: fixed; left: 0; top: 53px; bottom: 0; width: min(84vw, 330px); z-index: 25; transform: translateX(-102%); transition: transform .22s ease; box-shadow: 0 8px 30px rgba(0,0,0,.18); }
  #sidebar.open { transform: translateX(0); }
  #menu-toggle { display: block; }
  #content { min-width: 0; }
  #chapter { padding: 26px 16px 90px; }
  #welcome { padding: 44px 18px; }
  #welcome h1 { font-size: 27px; }
  .chapter-title { font-size: 24px; }
  .sec-title { font-size: 19px; }
  .sec-head { gap: 9px; }
  .viz-body { padding: 12px 12px 16px; }
  .viz-controls input[type=range] { width: 120px; }
  .viz-body > label input[type=range] { width: 120px; }
  .viz-controls { gap: 10px 16px; }
  .fig-multi img { flex: 1 1 140px; }
  .table-block table { font-size: 14.5px; }
  .table-block td, .table-block th { padding: 4px 8px; }
  .ch-nav { flex-direction: column; gap: 10px; }
  .ch-nav a[style] { text-align: left !important; }
  .footnotes { font-size: 13.5px; }
}