@import url('https://fonts.googleapis.com/css2?family=IBM+Plex+Sans:wght@400;500;600;700&family=IBM+Plex+Mono:wght@400;500;600&display=swap');

:root {
  --bg: #11100d;
  --paper: #f7f0e3;
  --paper-2: #efe3ce;
  --ink: #201a13;
  --muted: #6d604e;
  --rule: rgba(32, 26, 19, 0.16);
  --rule-strong: rgba(32, 26, 19, 0.32);
  --accent: #9f4f24;
  --accent-2: #1f6f68;
  --accent-3: #735f20;
  --code-bg: #171411;
  --code-text: #f2e8d5;
  --sidebar: #181511;
  --sidebar-text: #eadfc8;
  --sidebar-muted: #a99c84;
  font-family: 'IBM Plex Sans', system-ui, sans-serif;
  color: var(--ink);
  background: var(--bg);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; min-width: 320px; }
a { color: inherit; }
code, pre { font-family: 'IBM Plex Mono', monospace; }

* {
  scrollbar-color: rgba(159, 79, 36, 0.72) rgba(24, 21, 17, 0.18);
  scrollbar-width: thin;
}

*::-webkit-scrollbar {
  width: 11px;
  height: 11px;
}

*::-webkit-scrollbar-track {
  background: rgba(24, 21, 17, 0.14);
}

*::-webkit-scrollbar-thumb {
  background: linear-gradient(180deg, var(--accent), var(--accent-2));
  border: 2px solid rgba(247,240,227,0.58);
  border-radius: 999px;
}

*::-webkit-scrollbar-thumb:hover {
  background: linear-gradient(180deg, #b96330, #2b8179);
}

.skip-link {
  position: fixed;
  left: 14px;
  top: 10px;
  z-index: 40;
  transform: translateY(-160%);
  background: var(--paper);
  color: var(--ink);
  border: 2px solid var(--accent-2);
  border-radius: 6px;
  padding: 8px 10px;
}

.skip-link:focus {
  transform: translateY(0);
}

a:focus-visible,
button:focus-visible,
input:focus-visible {
  outline: 3px solid rgba(31,111,104,0.45);
  outline-offset: 2px;
}

.reading-progress {
  position: fixed;
  top: 0;
  left: 0;
  z-index: 30;
  width: 100%;
  height: 3px;
  background: var(--accent-2);
  transform: scaleX(0);
  transform-origin: 0 50%;
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  height: 60px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  padding: 0 24px;
  color: var(--sidebar-text);
  background: rgba(24, 21, 17, 0.94);
  border-bottom: 1px solid rgba(255,255,255,0.12);
  backdrop-filter: blur(14px);
}

.brand {
  font-family: 'IBM Plex Mono', monospace;
  font-weight: 700;
  text-decoration: none;
}

.topbar nav {
  display: flex;
  align-items: center;
  gap: 16px;
  color: var(--sidebar-muted);
  font-size: 14px;
}

.topbar nav a { text-decoration: none; }

.sidebar-toggle {
  border: 1px solid rgba(217,189,132,0.35);
  background: rgba(217,189,132,0.1);
  color: var(--sidebar-text);
  border-radius: 6px;
  padding: 7px 10px;
  font: inherit;
  cursor: pointer;
}

.sidebar-toggle:hover {
  background: rgba(217,189,132,0.18);
}

.book-layout {
  display: grid;
  grid-template-columns: 330px minmax(0, 1fr);
  min-height: calc(100vh - 60px);
  transition: grid-template-columns 180ms ease;
}

body.sidebar-collapsed .book-layout {
  grid-template-columns: 0 minmax(0, 1fr);
}

.sidebar {
  position: sticky;
  top: 60px;
  height: calc(100vh - 60px);
  overflow: auto;
  background:
    linear-gradient(rgba(255,255,255,0.035) 1px, transparent 1px),
    var(--sidebar);
  background-size: 100% 32px;
  color: var(--sidebar-text);
  padding: 24px 18px 40px;
  border-right: 1px solid rgba(255,255,255,0.1);
  transition: padding 180ms ease, border-color 180ms ease, opacity 140ms ease;
}

body.sidebar-collapsed .sidebar {
  padding: 0;
  border-color: transparent;
  opacity: 0;
  overflow: hidden;
  pointer-events: none;
}

.sidebar-title {
  font-family: 'IBM Plex Mono', monospace;
  font-weight: 700;
  color: #d9bd84;
  margin-bottom: 16px;
}

.book-search {
  display: block;
  margin-bottom: 22px;
}

.book-search span {
  display: block;
  margin-bottom: 8px;
  color: var(--sidebar-muted);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.book-search input {
  width: 100%;
  border: 1px solid rgba(255,255,255,0.16);
  border-radius: 6px;
  background: rgba(255,255,255,0.07);
  color: var(--sidebar-text);
  font: inherit;
  font-size: 14px;
  padding: 10px 11px;
  outline: none;
}

.book-search input:focus {
  border-color: rgba(217, 189, 132, 0.55);
  box-shadow: 0 0 0 3px rgba(217, 189, 132, 0.12);
}

.book-search input::placeholder {
  color: rgba(234,223,200,0.5);
}

.nav-part {
  margin-bottom: 24px;
}

.nav-part h3 {
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--sidebar-muted);
  margin: 0 0 8px;
}

.nav-part a {
  display: grid;
  grid-template-columns: 38px 1fr;
  gap: 8px;
  padding: 8px 10px;
  border-radius: 6px;
  text-decoration: none;
  color: var(--sidebar-text);
  line-height: 1.25;
  font-size: 14px;
}

.nav-part a span {
  color: var(--sidebar-muted);
  font-family: 'IBM Plex Mono', monospace;
}

.nav-part a.active,
.nav-part a:hover {
  background: rgba(217, 189, 132, 0.12);
}

.nav-part[hidden],
.nav-part a[hidden] {
  display: none;
}

.page {
  min-width: 0;
  background:
    radial-gradient(circle at 12% 0%, rgba(159, 79, 36, 0.14), transparent 32rem),
    linear-gradient(90deg, rgba(32,26,19,0.04) 1px, transparent 1px),
    var(--paper);
  background-size: auto, 32px 32px, auto;
}

.page-hero {
  padding: clamp(42px, 7vw, 96px) clamp(20px, 6vw, 96px) 28px;
  border-bottom: 1px solid var(--rule);
}

.eyebrow {
  font-family: 'IBM Plex Mono', monospace;
  font-weight: 700;
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--accent);
  margin: 0 0 14px;
}

h1 {
  font-size: clamp(42px, 7vw, 90px);
  line-height: 0.95;
  letter-spacing: 0;
  max-width: 1040px;
  margin: 0 0 18px;
}

.subtitle {
  max-width: 920px;
  color: var(--muted);
  font-size: clamp(18px, 2vw, 24px);
  line-height: 1.55;
  margin: 0;
}

.source-note {
  margin: 18px 0 0;
  color: var(--muted);
  font-size: 14px;
}

.source-note code {
  background: rgba(32,26,19,0.08);
  border: 1px solid var(--rule);
  border-radius: 4px;
  padding: 2px 5px;
}

.content-shell {
  display: grid;
  grid-template-columns: minmax(0, 920px) 260px;
  gap: clamp(24px, 5vw, 72px);
  align-items: start;
  padding: 38px clamp(20px, 6vw, 96px) 96px;
}

.prose {
  min-width: 0;
}

.prose h2 {
  font-size: clamp(30px, 4vw, 48px);
  line-height: 1.06;
  margin: 54px 0 18px;
  padding-top: 12px;
  border-top: 2px solid var(--rule);
}

.prose h3 {
  font-size: clamp(23px, 3vw, 32px);
  margin: 36px 0 14px;
  color: var(--accent);
}

.prose h4 {
  font-size: 20px;
  margin: 28px 0 10px;
}

.prose p,
.prose li,
.prose blockquote {
  font-size: clamp(17px, 1.4vw, 20px);
  line-height: 1.78;
}

.prose p,
.prose ul,
.prose ol,
.prose blockquote {
  margin-bottom: 20px;
}

.prose li {
  margin: 8px 0;
}

.prose code {
  background: rgba(32,26,19,0.09);
  border: 1px solid var(--rule);
  border-radius: 4px;
  padding: 0 4px;
  font-size: 0.88em;
}

pre {
  position: relative;
  overflow: auto;
  background: var(--code-bg);
  color: var(--code-text);
  border-radius: 8px;
  padding: 20px;
  border: 1px solid rgba(0,0,0,0.28);
  box-shadow: inset 0 1px 0 rgba(255,255,255,0.06);
}

.diagram-shell {
  margin: 28px 0;
  overflow-x: auto;
  border: 1px solid var(--rule);
  border-radius: 8px;
  background: rgba(255,255,255,0.34);
  padding: 18px;
}

.mermaid {
  min-width: 560px;
  text-align: center;
}

.mermaid svg {
  max-width: 100%;
  height: auto;
}

.mermaid-failed {
  color: var(--accent);
  font-family: 'IBM Plex Mono', monospace;
  text-align: left;
  white-space: pre;
}

.table-wrap {
  overflow-x: auto;
  margin: 24px 0;
  border: 1px solid var(--rule);
  border-radius: 8px;
  background: rgba(255,255,255,0.24);
}

table {
  width: 100%;
  min-width: 620px;
  border-collapse: collapse;
}

th,
td {
  border-bottom: 1px solid var(--rule);
  padding: 11px 13px;
  text-align: left;
  vertical-align: top;
  font-size: 15px;
  line-height: 1.5;
}

th {
  background: rgba(32,26,19,0.08);
  color: var(--accent);
  font-weight: 700;
}

tr:last-child td {
  border-bottom: 0;
}

pre code {
  background: transparent !important;
  border: 0 !important;
  color: inherit;
  padding: 0 !important;
  font-size: 14px;
  line-height: 1.62;
}

.copy-code {
  position: absolute;
  top: 10px;
  right: 10px;
  border: 1px solid rgba(255,255,255,0.18);
  background: rgba(255,255,255,0.08);
  color: var(--code-text);
  border-radius: 5px;
  padding: 5px 8px;
  cursor: pointer;
}

blockquote {
  border-left: 4px solid var(--accent-2);
  background: rgba(31,111,104,0.09);
  padding: 16px 18px;
  margin-left: 0;
}

.chapter-toc {
  position: sticky;
  top: 86px;
  background: rgba(255,255,255,0.32);
  border: 1px solid var(--rule);
  border-radius: 8px;
  padding: 16px;
}

.chapter-toc strong {
  display: block;
  margin-bottom: 10px;
}

.chapter-toc a {
  display: block;
  text-decoration: none;
  color: var(--muted);
  font-size: 14px;
  line-height: 1.35;
  padding: 6px 0;
}

.chapter-toc a.active {
  color: var(--accent);
  font-weight: 700;
}

.index-intro p {
  font-size: clamp(19px, 2vw, 25px);
  line-height: 1.62;
  max-width: 1040px;
}

.coverage-strip {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 12px;
  margin: 34px 0 52px;
}

.coverage-strip div,
.chapter-card {
  border: 1px solid var(--rule);
  background: rgba(255,255,255,0.32);
  border-radius: 8px;
  padding: 18px;
}

.coverage-strip strong {
  display: block;
  font-size: 32px;
  color: var(--accent);
}

.coverage-strip span {
  color: var(--muted);
}

.part-index {
  margin-top: 48px;
}

.chapter-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 14px;
}

.chapter-card {
  display: block;
  text-decoration: none;
  min-height: 190px;
}

.chapter-card span {
  font-family: 'IBM Plex Mono', monospace;
  color: var(--accent-2);
  font-weight: 700;
}

.chapter-card h3 {
  margin: 14px 0 10px;
  font-size: 22px;
}

.chapter-card p {
  color: var(--muted);
  line-height: 1.5;
}

.pager {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 20px;
  margin-top: 72px;
  padding-top: 24px;
  border-top: 1px solid var(--rule);
}

.pager-link {
  display: block;
  min-height: 112px;
  border: 1px solid var(--rule);
  border-radius: 8px;
  background: rgba(255,255,255,0.28);
  padding: 18px;
  color: var(--ink);
  text-decoration: none;
}

.pager-link:hover {
  border-color: var(--rule-strong);
  background: rgba(255,255,255,0.42);
}

.pager-link span {
  display: block;
  color: var(--accent-2);
  font-family: 'IBM Plex Mono', monospace;
  font-size: 12px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 10px;
}

.pager-link strong {
  display: block;
  font-size: 20px;
  line-height: 1.25;
}

.pager-link.previous::before,
.pager-link.next::before {
  color: var(--accent);
  font-family: 'IBM Plex Mono', monospace;
  font-weight: 700;
}

.pager-link.previous::before {
  content: "<-";
}

.pager-link.next {
  text-align: right;
}

.pager-link.next::before {
  content: "->";
}

@media (max-width: 1180px) {
  .book-layout {
    grid-template-columns: 1fr;
  }
  .sidebar {
    position: static;
    height: auto;
    max-height: 360px;
    padding-top: 18px;
  }
  .content-shell {
    grid-template-columns: 1fr;
  }
  .chapter-toc {
    position: static;
    order: -1;
  }
  .chapter-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 720px) {
  .topbar {
    height: auto;
    min-height: 60px;
    align-items: flex-start;
    flex-direction: column;
    padding: 14px 18px;
  }
  .topbar nav {
    flex-wrap: wrap;
  }
  .coverage-strip,
  .chapter-grid,
  .pager {
    grid-template-columns: 1fr;
  }
  .page-hero,
  .content-shell {
    padding-left: 18px;
    padding-right: 18px;
  }
}