:root {
  --bg: #101412;
  --bg-soft: #17201c;
  --panel: rgba(245, 241, 229, 0.06);
  --panel-strong: rgba(245, 241, 229, 0.1);
  --text: #f6f0df;
  --text-soft: #d9cfb8;
  --text-dim: #a99f89;
  --line: rgba(240, 201, 106, 0.2);
  --primary: #f0c96a;
  --accent: #69b3a2;
  --danger: #ee8877;
  --reading-width: 47rem;
  --header-height: 56px;
  --font-sans: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", monospace;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: calc(var(--header-height) + 20px); }
html, body { overflow-x: hidden; }
body {
  margin: 0;
  min-height: 100vh;
  color: var(--text);
  font-family: var(--font-sans);
  line-height: 1.85;
  font-size: 1.0625rem;
  background:
    linear-gradient(115deg, rgba(105, 179, 162, 0.12), transparent 34%),
    linear-gradient(245deg, rgba(240, 201, 106, 0.13), transparent 30%),
    linear-gradient(180deg, #0f1412 0%, #111714 54%, #0d1110 100%);
  background-attachment: fixed;
}
a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }

.book-header {
  position: fixed;
  inset: 0 0 auto 0;
  z-index: 50;
  height: var(--header-height);
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0 1rem;
  background: rgba(13, 18, 16, 0.86);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(14px);
}
.book-header__menu, .book-header__home {
  border: 1px solid var(--line);
  background: rgba(255, 255, 255, 0.04);
  color: var(--text);
  min-height: 40px;
}
.book-header__menu {
  width: 40px;
  border-radius: 8px;
  cursor: pointer;
  font-size: 1.1rem;
}
.book-header__home {
  display: inline-flex;
  align-items: center;
  padding: 0 0.75rem;
  border-radius: 8px;
  font-weight: 750;
  white-space: nowrap;
}
.book-header__current {
  min-width: 0;
  flex: 1;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  color: var(--text-dim);
  font-size: 0.95rem;
}
.book-progress {
  position: fixed;
  top: var(--header-height);
  left: 0;
  z-index: 51;
  height: 3px;
  width: 0;
  background: linear-gradient(90deg, var(--primary), var(--accent));
}

.book-toc-backdrop {
  position: fixed;
  inset: 0;
  z-index: 60;
  background: rgba(0, 0, 0, 0.48);
  opacity: 0;
  pointer-events: none;
  transition: opacity 180ms ease;
}
.book-toc-backdrop.is-open { opacity: 1; pointer-events: auto; }
.book-toc {
  position: fixed;
  top: 0;
  left: 0;
  bottom: 0;
  z-index: 61;
  width: min(25rem, 86vw);
  padding: 1rem;
  overflow-y: auto;
  background: #121915;
  border-right: 1px solid var(--line);
  display: none;
  transform: translateX(calc(-100% - 24px));
}
.book-toc.is-open { display: block; transform: translateX(0); visibility: visible; }
.book-toc__title {
  margin: 0.25rem 0 1rem;
  color: var(--primary);
  font-weight: 850;
}
.book-toc__part {
  margin: 1rem 0 0.35rem;
  color: var(--text-dim);
  font-size: 0.86rem;
}
.book-toc__link {
  display: grid;
  grid-template-columns: 2.5rem 1fr;
  gap: 0.5rem;
  padding: 0.55rem 0.65rem;
  border-radius: 8px;
  color: var(--text-soft);
}
.book-toc__link:hover, .book-toc__link.is-current {
  background: rgba(240, 201, 106, 0.11);
  color: var(--text);
  text-decoration: none;
}

.book-layout {
  width: 100%;
}

.book-layout__main {
  min-width: 0;
}

.book-rail--chapters { grid-column: 1; }
.book-layout__main { grid-column: 2; }
.book-rail--outline { grid-column: 3; }

.book-rail {
  display: none;
}

.book-rail__title {
  margin: 0 0 0.75rem;
  color: var(--primary);
  font-weight: 850;
  font-size: 0.92rem;
}

.book-rail__list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.book-rail__part {
  margin: 1rem 0 0.35rem;
  color: var(--text-dim);
  font-size: 0.78rem;
  font-weight: 800;
}

.book-rail__part:first-child {
  margin-top: 0;
}

.book-rail__link,
.book-rail__outline-link {
  display: grid;
  gap: 0.25rem;
  padding: 0.46rem 0.55rem;
  border-radius: 8px;
  color: var(--text-soft);
  line-height: 1.35;
}

.book-rail__link {
  grid-template-columns: 2.2rem minmax(0, 1fr);
}

.book-rail__link:hover,
.book-rail__outline-link:hover {
  background: rgba(240, 201, 106, 0.1);
  color: var(--text);
  text-decoration: none;
}

.book-rail__link.is-current,
.book-rail__outline-link.is-current {
  background: rgba(240, 201, 106, 0.15);
  color: var(--text);
}

.book-rail__num {
  color: var(--accent);
  font-size: 0.8rem;
  font-weight: 850;
}

.book-rail__name {
  min-width: 0;
  overflow-wrap: anywhere;
}

.book-rail__outline-item--sub .book-rail__outline-link {
  padding-left: 1.25rem;
  font-size: 0.9rem;
  color: var(--text-dim);
}

.book-rail__empty {
  margin: 0;
  color: var(--text-dim);
  font-size: 0.9rem;
}

.cover {
  min-height: 78vh;
  display: grid;
  place-items: center;
  padding: 7rem 1.25rem 4rem;
}
.cover__inner {
  width: min(68rem, 100%);
}
.cover__eyebrow, .chapter__eyebrow, .toc-part {
  color: var(--primary);
  font-weight: 800;
  letter-spacing: 0;
}
.cover h1 {
  margin: 0;
  max-width: 12ch;
  font-size: clamp(3.2rem, 7vw, 6.5rem);
  line-height: 1.02;
  letter-spacing: 0;
}
.cover__lead {
  max-width: 48rem;
  color: var(--text-soft);
  font-size: 1.22rem;
}
.cover__actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.8rem;
  margin: 2rem 0 1rem;
}
.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 0.55rem 1rem;
  border-radius: 8px;
  border: 1px solid var(--line);
  font-weight: 800;
}
.button--primary { background: var(--primary); color: #15130c; }
.button--ghost { color: var(--text); background: rgba(255,255,255,0.05); }
.muted { color: var(--text-dim); }

.toc-section {
  width: min(72rem, calc(100% - 2rem));
  margin: 0 auto 5rem;
}
.toc-section h2 {
  margin-top: 0;
  font-size: 2rem;
}
.toc-section__hint { color: var(--text-soft); }
.toc-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.9rem;
  margin-bottom: 2rem;
}
.toc-card {
  display: grid;
  gap: 0.25rem;
  min-height: 9.5rem;
  padding: 1rem;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.045);
  color: var(--text);
}
.toc-card:hover {
  text-decoration: none;
  border-color: rgba(240, 201, 106, 0.42);
  background: rgba(255, 255, 255, 0.07);
}
.toc-card__num { color: var(--accent); font-weight: 800; font-size: 0.92rem; }
.toc-card__title { font-size: 1.18rem; font-weight: 850; }
.toc-card__desc { color: var(--text-soft); font-size: 0.96rem; }

.chapter {
  padding: calc(var(--header-height) + 2.4rem) 1.2rem 2rem;
}
.chapter__inner {
  max-width: var(--reading-width);
  margin: 0 auto;
}
.chapter h1 {
  margin: 0 0 1rem;
  font-size: clamp(2rem, 5vw, 2.9rem);
  line-height: 1.14;
  letter-spacing: 0;
}
.lead {
  margin: 0 0 2.5rem;
  color: var(--text);
  font-size: 1.18rem;
  line-height: 1.8;
}
.chapter p {
  margin: 1rem 0;
  color: var(--text-soft);
}
.chapter h2 {
  margin: 3rem 0 1rem;
  padding-top: 0.6rem;
  font-size: clamp(1.5rem, 3.4vw, 2rem);
  line-height: 1.2;
  letter-spacing: 0;
}
.chapter h3 {
  margin: 2.2rem 0 0.8rem;
  font-size: 1.28rem;
  color: var(--text);
}
.summary, .quiz, .glossary-list, .references {
  border-left: 2px solid rgba(240, 201, 106, 0.28);
  padding-left: 1.1rem;
}
ul, ol { padding-left: 1.35rem; }
li + li { margin-top: 0.25rem; }
strong { color: #fff7df; }

.table-wrap {
  overflow-x: auto;
  margin: 1.2rem 0;
}
table {
  width: 100%;
  border-collapse: collapse;
  min-width: 40rem;
  background: rgba(255, 255, 255, 0.035);
}
th, td {
  border: 1px solid rgba(240, 201, 106, 0.18);
  padding: 0.68rem 0.75rem;
  vertical-align: top;
}
th {
  color: var(--primary);
  text-align: left;
  background: rgba(240, 201, 106, 0.07);
}

pre {
  max-width: 100%;
  overflow-x: auto;
  white-space: pre;
}

code {
  font-family: var(--font-mono);
}

.code-walk__code {
  display: block;
  margin: 1rem 0;
  padding: 1rem;
  border: 1px solid rgba(240, 201, 106, 0.18);
  border-radius: 8px;
  background: rgba(0, 0, 0, 0.22);
  color: var(--text-soft);
  line-height: 1.55;
}

.callout {
  margin: 1.2rem 0;
  padding: 1rem;
  border: 1px solid rgba(105, 179, 162, 0.35);
  border-radius: 8px;
  background: rgba(105, 179, 162, 0.08);
}

.objectives {
  margin: 1.6rem 0 2rem;
  padding: 1.1rem 1.3rem;
  border: 1px solid var(--line);
  border-radius: 20px;
  background: var(--panel);
}

.objectives h2 {
  margin: 0 0 0.6rem;
  padding: 0;
  border: 0;
  color: var(--accent);
  font-size: 1rem;
}

.objectives ul {
  margin: 0;
}

.figure {
  margin: 1.8rem 0 2.2rem;
}

.figure--reading {
  padding: 0;
}

.chapter-map {
  display: block;
  width: 100%;
  height: auto;
  border-radius: 20px;
}

.chapter-diagram {
  display: block;
  width: 100%;
  height: auto;
  border-radius: 20px;
  background: rgba(18, 29, 49, 0.55);
  border: 1px solid rgba(105, 179, 162, 0.22);
  padding: 0.4rem;
}

.figure__cap {
  margin: 0.55rem 0 0;
  color: var(--text-dim);
  font-size: 0.92rem;
  text-align: center;
}
.summary {
  margin-top: 3rem;
  padding: 1rem 1rem 1rem 1.25rem;
  border: 1px solid rgba(240, 201, 106, 0.22);
  border-radius: 8px;
  background: rgba(240, 201, 106, 0.06);
}
.summary h2, .quiz h2, .glossary-list h2, .references h2 { margin-top: 0; }
.quiz {
  margin-top: 2rem;
  padding: 1rem 0 0 1.1rem;
}
.quiz__item {
  margin: 0.8rem 0;
  padding: 0.8rem 1rem;
  border: 1px solid rgba(255,255,255,0.12);
  border-radius: 8px;
  background: rgba(255,255,255,0.04);
}
.quiz__item summary {
  cursor: pointer;
  font-weight: 800;
  color: var(--text);
}
.quiz__item p { color: var(--text-soft); }

.map-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.8rem;
  margin: 1.2rem 0;
}
.map-grid div {
  min-height: 7rem;
  padding: 1rem;
  border: 1px solid rgba(240, 201, 106, 0.2);
  border-radius: 8px;
  background: rgba(255,255,255,0.045);
}
.map-grid strong, .map-grid span { display: block; }
.map-grid span { color: var(--text-soft); margin-top: 0.35rem; }

.glossary-list ul {
  list-style: none;
  padding: 0;
}
.glossary-list li {
  padding: 1rem 0;
  border-bottom: 1px solid rgba(255,255,255,0.1);
}
.glossary-list p { margin: 0.2rem 0 0; color: var(--text-soft); }
.references li { overflow-wrap: anywhere; }

.chapter-nav {
  width: min(var(--reading-width), calc(100% - 2rem));
  margin: 3rem auto 0;
  display: flex;
  justify-content: space-between;
  gap: 1rem;
}
.chapter-nav a {
  flex: 1;
  padding: 0.9rem 1rem;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: rgba(255,255,255,0.04);
  color: var(--text);
}
.chapter-nav a:last-child { text-align: right; }

.reveal { opacity: 0; transform: translateY(10px); transition: opacity 260ms ease, transform 260ms ease; }
.reveal.is-visible { opacity: 1; transform: none; }

@media (max-width: 760px) {
  body { font-size: 1rem; }
  .cover { min-height: 72vh; padding-top: 6rem; }
  .cover h1 { font-size: 3rem; }
  .cover__lead, .lead { font-size: 1.08rem; }
  .toc-grid, .map-grid { grid-template-columns: 1fr; }
  .toc-card { min-height: auto; }
  .chapter { padding-left: 1rem; padding-right: 1rem; }
  .chapter h1 { font-size: 2.25rem; }
  .chapter h2 { font-size: 1.42rem; }
  .summary, .quiz, .glossary-list, .references { padding-left: 0.85rem; }
  .book-header__home { max-width: 7.5rem; overflow: hidden; text-overflow: ellipsis; }
}

@media (min-width: 1180px) {
  .chapter {
    padding: calc(var(--header-height) + 1.4rem) 1rem 4rem;
  }

  .book-layout {
    display: grid;
    grid-template-columns: 220px minmax(0, var(--reading-width)) minmax(180px, 220px);
    gap: 2rem;
    align-items: start;
    max-width: 1280px;
    width: auto;
    margin: 0 auto;
  }

  .book-layout__main .chapter__inner {
    width: 100%;
    max-width: none;
    margin: 0;
  }

  .book-rail {
    display: block;
    position: sticky;
    top: calc(var(--header-height) + 1.25rem);
    max-height: calc(100vh - var(--header-height) - 2rem);
    overflow-y: auto;
    padding: 0.2rem 0.2rem 1rem 0;
    border: 0;
    border-radius: 0;
    background: transparent;
    scrollbar-width: none;
  }

  .book-rail.is-fixed {
    position: fixed;
    top: calc(var(--header-height) + 1.25rem);
    z-index: 20;
  }

  .book-rail::-webkit-scrollbar {
    width: 0;
    height: 0;
    display: none;
  }

  .book-rail::-webkit-scrollbar-thumb {
    background: rgba(240, 201, 106, 0.25);
    border-radius: 999px;
  }

  .chapter-nav {
    width: 100%;
  }
}

@media (min-width: 1320px) {
  .book-layout {
    max-width: 1480px;
    grid-template-columns: 248px minmax(0, 52rem) 248px;
    gap: 2.4rem;
  }
}

@media (min-width: 1680px) {
  .book-layout {
    max-width: 1600px;
    grid-template-columns: 280px minmax(0, 56rem) 300px;
    gap: 3rem;
  }
}