/* ============================================================
   AI Engineering Interview Handbook — 2026 Senior GenAI edition
   Light-only premium design system. Offline-first, no CDN calls.
   Fonts and Mermaid are vendored locally under assets/.
   ============================================================ */

/* ---------- Self-hosted fonts ---------- */
@font-face { font-family: "Inter"; src: url("fonts/inter-400.woff2") format("woff2"); font-weight: 400; font-style: normal; font-display: swap; }
@font-face { font-family: "Inter"; src: url("fonts/inter-500.woff2") format("woff2"); font-weight: 500; font-style: normal; font-display: swap; }
@font-face { font-family: "Inter"; src: url("fonts/inter-600.woff2") format("woff2"); font-weight: 600; font-style: normal; font-display: swap; }
@font-face { font-family: "Inter"; src: url("fonts/inter-700.woff2") format("woff2"); font-weight: 700; font-style: normal; font-display: swap; }
@font-face { font-family: "Inter"; src: url("fonts/inter-800.woff2") format("woff2"); font-weight: 800; font-style: normal; font-display: swap; }
@font-face { font-family: "Fraunces"; src: url("fonts/fraunces-500.woff2") format("woff2"); font-weight: 500; font-style: normal; font-display: swap; }
@font-face { font-family: "Fraunces"; src: url("fonts/fraunces-600.woff2") format("woff2"); font-weight: 600; font-style: normal; font-display: swap; }
@font-face { font-family: "Fraunces"; src: url("fonts/fraunces-700.woff2") format("woff2"); font-weight: 700; font-style: normal; font-display: swap; }
@font-face { font-family: "JetBrains Mono"; src: url("fonts/jetbrains-mono-400.woff2") format("woff2"); font-weight: 400; font-style: normal; font-display: swap; }
@font-face { font-family: "JetBrains Mono"; src: url("fonts/jetbrains-mono-600.woff2") format("woff2"); font-weight: 600; font-style: normal; font-display: swap; }

/* ---------- Design tokens ---------- */
:root {
  --nav-width: 284px;
  --top-height: 68px;

  --canvas: #f8faff;
  --paper: #ffffff;
  --paper-warm: #f0f5ff;
  --tint: #eff6ff;
  --ink: #0f172a;
  --ink-soft: #475569;
  --muted: #94a3b8;
  --line: #e2e8f0;
  --line-strong: #cbd5e1;

  --forest: #0f172a;
  --forest-2: #1e3a8a;
  --green: #1d4ed8;
  --green-bright: #3b82f6;
  --green-soft: #dbeafe;
  --gold: #d3a13f;
  --gold-soft: #f7ecd3;

  --aws: #c9720d;
  --aws-soft: #fdf2e2;
  --gcp: #2f6fdb;
  --gcp-soft: #e9f0fd;

  --font-body: "Inter", ui-sans-serif, system-ui, -apple-system, "Segoe UI", sans-serif;
  --font-display: "Fraunces", Georgia, "Times New Roman", serif;
  --font-mono: "JetBrains Mono", ui-monospace, SFMono-Regular, Consolas, monospace;

  --shadow-sm: 0 2px 10px rgba(15, 23, 42, .06);
  --shadow-md: 0 10px 32px rgba(15, 23, 42, .10);
  --shadow-lg: 0 24px 70px rgba(15, 23, 42, .15);
  --radius: 16px;
  --radius-sm: 10px;
  --reader-size: 1rem;

  /* default accent, overridden by .accent-* */
  --acc: var(--green);
  --acc-soft: var(--green-soft);
  --acc-ink: #1e3a8a;

  color-scheme: light only;
}

/* 16 chapter accent families */
.accent-sage   { --acc: #4e7d5b; --acc-soft: #e7efe6; --acc-ink: #2c4a35; }
.accent-violet { --acc: #6d5bd0; --acc-soft: #ebe8fa; --acc-ink: #3e3382; }
.accent-amber  { --acc: #b97d10; --acc-soft: #f9efd8; --acc-ink: #6d4a09; }
.accent-teal   { --acc: #0f766e; --acc-soft: #dcf0ee; --acc-ink: #0b4f4a; }
.accent-iris   { --acc: #5964d6; --acc-soft: #e7e9fb; --acc-ink: #333c8f; }
.accent-gold   { --acc: #b28a24; --acc-soft: #f7eed4; --acc-ink: #6b5312; }
.accent-blue   { --acc: #2569c3; --acc-soft: #e3edfa; --acc-ink: #163f78; }
.accent-orange { --acc: #c9720d; --acc-soft: #fdf0dd; --acc-ink: #7c4507; }
.accent-cobalt { --acc: #3b66e0; --acc-soft: #e6ecfc; --acc-ink: #23408f; }
.accent-indigo { --acc: #4956c4; --acc-soft: #e6e8f9; --acc-ink: #2b3478; }
.accent-rose   { --acc: #bb3a5c; --acc-soft: #f9e4ea; --acc-ink: #77243b; }
.accent-slate  { --acc: #52627a; --acc-soft: #e8ecf2; --acc-ink: #32405a; }
.accent-mint   { --acc: #199a72; --acc-soft: #def3ea; --acc-ink: #0e5c45; }
.accent-cyan   { --acc: #0e7f9c; --acc-soft: #def0f5; --acc-ink: #0a4f62; }
.accent-lime   { --acc: #5c7f1e; --acc-soft: #edf3da; --acc-ink: #3a5013; }
.accent-bronze { --acc: #9a6b32; --acc-soft: #f4ebdd; --acc-ink: #5f4120; }
/* legacy aliases used by earlier builds */
.accent-sage, .accent-teal, .accent-violet, .accent-amber, .accent-blue,
.accent-indigo, .accent-rose, .accent-orange, .accent-mint, .accent-cyan,
.accent-lime, .accent-gold { /* kept */ }

* { box-sizing: border-box; }

html { scroll-behavior: smooth; scroll-padding-top: calc(var(--top-height) + 24px); }

body {
  margin: 0;
  background: var(--canvas);
  color: var(--ink);
  font-family: var(--font-body);
  font-size: var(--reader-size);
  line-height: 1.68;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
}
body.reader-large { --reader-size: 1.09rem; }
body[data-font-size="-2"] { --reader-size: 0.82rem; }
body[data-font-size="-1"] { --reader-size: 0.91rem; }
body[data-font-size="1"]  { --reader-size: 1.09rem; }
body[data-font-size="2"]  { --reader-size: 1.18rem; }

button, input, select, textarea { font: inherit; color: inherit; }
button, a { -webkit-tap-highlight-color: transparent; }
a { color: inherit; }
img, svg { max-width: 100%; }
svg { width: 1.2rem; height: 1.2rem; fill: none; stroke: currentColor; stroke-width: 1.8; stroke-linecap: round; stroke-linejoin: round; }
::selection { background: #bfdbfe; color: #0c1a4c; }

:focus-visible { outline: 2px solid var(--green-bright); outline-offset: 2px; border-radius: 4px; }

.sr-only {
  position: absolute !important; width: 1px; height: 1px;
  padding: 0; margin: -1px; overflow: hidden;
  clip: rect(0, 0, 0, 0); white-space: nowrap; border: 0;
}

.skip-link {
  position: fixed; left: 1rem; top: -5rem; z-index: 1000;
  background: var(--gold); color: #17201b;
  padding: .7rem 1rem; border-radius: .55rem; font-weight: 800; text-decoration: none;
}
.skip-link:focus { top: 1rem; }

.app-shell { min-height: 100vh; }
.page-shell { width: calc(100% - var(--nav-width)); margin-left: var(--nav-width); min-height: 100vh; display: flex; flex-direction: column; }
.page-shell main { flex: 1; }

/* ============================================================
   Sidebar
   ============================================================ */
.site-nav {
  position: fixed; inset: 0 auto 0 0; z-index: 60;
  width: var(--nav-width); padding: 1.4rem 1rem 1.2rem;
  display: flex; flex-direction: column;
  color: #c8d5e8;
  background:
    radial-gradient(circle at 20% -4%, rgba(59, 130, 246, .22), transparent 32%),
    radial-gradient(circle at 90% 110%, rgba(147, 197, 253, .08), transparent 34%),
    linear-gradient(178deg, #0f172a 0%, #0a1322 100%);
  overflow-y: auto; scrollbar-width: thin; scrollbar-color: rgba(255,255,255,.22) transparent;
}
.nav-head { display: flex; align-items: flex-start; justify-content: space-between; padding: .15rem .4rem 1.15rem; }
.wordmark { display: flex; align-items: center; gap: .7rem; color: #ccd9f0; text-decoration: none; font-size: .82rem; line-height: 1.12; letter-spacing: .01em; }
.wordmark strong { color: #fff; font-size: .98rem; }
.wordmark-mark {
  width: 2.6rem; height: 2.6rem; display: grid; place-items: center; flex: none;
  border-radius: .85rem; color: #0c1445; font-weight: 800; letter-spacing: -.03em; font-size: .95rem;
  background: linear-gradient(140deg, #efd292, #cf9c37); box-shadow: 0 4px 14px rgba(0,0,0,.28);
}
.nav-close { display: none; border: 0; background: transparent; color: #9dbde0; font-size: 1.8rem; cursor: pointer; }
.nav-main { display: grid; gap: .16rem; padding: 0 .05rem .95rem; border-bottom: 1px solid rgba(213, 233, 225, .13); }
.nav-main a { display: flex; align-items: center; gap: .7rem; padding: .62rem .72rem; border-radius: .6rem; color: #93b4d4; text-decoration: none; font-size: .82rem; font-weight: 600; }
.nav-main a:hover, .nav-main a:focus-visible { color: #fff; background: rgba(255, 255, 255, .08); }
.nav-main svg { width: 1.02rem; }
.nav-label { margin: 1rem .7rem .4rem; color: #4a6fa5; font-size: .6rem; letter-spacing: .16em; font-weight: 800; }
.chapter-nav { display: grid; gap: .05rem; }
.chapter-nav a {
  display: grid; grid-template-columns: 1.5rem 1fr .6rem; align-items: center; gap: .4rem;
  min-height: 1.95rem; padding: .4rem .6rem; border-radius: .5rem;
  color: #8da3c0; text-decoration: none; font-size: .69rem; line-height: 1.25;
}
.chapter-nav a > span:first-child { color: #4a6fa5; font-size: .58rem; font-weight: 800; letter-spacing: .05em; }
.chapter-nav a:hover, .chapter-nav a:focus-visible, .chapter-nav a.active { color: #fff; background: rgba(255, 255, 255, .08); }
.chapter-nav a.active { box-shadow: inset 2px 0 0 var(--gold); }
.chapter-nav a.active > span:first-child { color: #efd292; }
.chapter-nav i { width: .4rem; height: .4rem; border-radius: 50%; justify-self: end; background: transparent; }
.chapter-nav i.done { background: #60a5fa; box-shadow: 0 0 0 3px rgba(96, 165, 250, .16); }
.nav-progress { margin-top: auto; padding: 1.2rem .65rem .1rem; color: #8da3c0; font-size: .68rem; }
.nav-progress > div:first-child { display: flex; justify-content: space-between; margin-bottom: .5rem; }
.nav-progress strong { color: #fff; }
.nav-progress small { display: block; margin-top: .5rem; color: #4a6fa5; }

.progress-track { height: .36rem; overflow: hidden; border-radius: 999px; background: rgba(120, 144, 136, .28); }
.progress-track i { display: block; width: 0; height: 100%; border-radius: inherit; background: linear-gradient(90deg, var(--gold), #ecca77); transition: width .35s ease; }

.nav-scrim { display: none; }

/* ============================================================
   Top bar
   ============================================================ */
.topbar {
  position: sticky; top: 0; z-index: 45; height: var(--top-height);
  display: flex; align-items: center; gap: 1rem;
  padding: 0 clamp(1rem, 3.6vw, 3.4rem);
  border-bottom: 1px solid var(--line);
  background: color-mix(in srgb, var(--paper-warm) 88%, transparent);
  backdrop-filter: blur(14px);
}
.menu-button { display: none !important; }
.mobile-title { display: none; text-decoration: none; font-size: .86rem; }
.mobile-title strong { color: var(--green); }
.search-trigger {
  width: min(34rem, 60%); display: flex; align-items: center; gap: .65rem;
  padding: .58rem .8rem; border: 1px solid var(--line); border-radius: .7rem;
  background: var(--paper); color: var(--muted); cursor: pointer; text-align: left;
  box-shadow: var(--shadow-sm);
}
.search-trigger:hover { border-color: #93c5fd; }
.search-trigger svg { width: .98rem; }
.search-trigger span { flex: 1; font-size: .78rem; }
kbd {
  padding: .08rem .38rem; border: 1px solid var(--line-strong); border-bottom-width: 2px;
  border-radius: .32rem; background: var(--paper); color: var(--muted);
  font-size: .63rem; font-family: var(--font-body);
}
.top-actions { display: flex; gap: .25rem; margin-left: auto; }
.icon-button {
  width: 2.4rem; height: 2.4rem; display: grid; place-items: center; padding: 0;
  border: 0; border-radius: .6rem; background: transparent; color: var(--ink-soft); cursor: pointer;
}
.icon-button:hover, .icon-button:focus-visible { background: var(--tint); color: var(--ink); }
.text-size { font-weight: 700; font-family: var(--font-display); font-size: .92rem; }

/* ============================================================
   Shared
   ============================================================ */
.overline { margin: 0; color: #60a5fa; font-size: .67rem; font-weight: 800; letter-spacing: .16em; }
.overline.dark { color: var(--green); }
.primary-action, .secondary-action {
  min-height: 2.95rem; display: inline-flex; align-items: center; justify-content: center; gap: .7rem;
  padding: .7rem 1.15rem; border: 1px solid transparent; border-radius: .72rem;
  text-decoration: none; font-weight: 700; font-size: .84rem; cursor: pointer;
}
.primary-action { background: var(--gold); color: #1a1f1a; box-shadow: 0 8px 22px rgba(211, 161, 63, .28); }
.primary-action:hover { background: #e0b154; transform: translateY(-1px); }
.primary-action svg { width: 1rem; }
.secondary-action { border-color: rgba(255, 255, 255, .3); color: #fff; }
.secondary-action:hover { background: rgba(255, 255, 255, .09); }
.section-heading { display: flex; align-items: flex-end; justify-content: space-between; gap: 2rem; margin-bottom: 2rem; }
.section-heading h2 { margin: .35rem 0 0; font-family: var(--font-display); font-weight: 600; font-size: clamp(1.9rem, 3.4vw, 3rem); line-height: 1.06; letter-spacing: -.02em; }
.section-heading > p { max-width: 24rem; margin: 0; color: var(--muted); font-size: .82rem; }
.section-heading.light h2 { color: #fff; }

/* ============================================================
   Homepage
   ============================================================ */
.home-hero {
  min-height: 37rem; display: grid; grid-template-columns: minmax(0, 1.14fr) minmax(19rem, .86fr);
  align-items: center; gap: clamp(2rem, 6vw, 6.5rem);
  padding: clamp(3.6rem, 7vw, 6.6rem) clamp(2rem, 6.4vw, 7rem);
  overflow: hidden; color: #fff;
  background:
    radial-gradient(circle at 84% 16%, rgba(59, 130, 246, .20), transparent 26%),
    radial-gradient(circle at 72% 88%, rgba(147, 197, 253, .12), transparent 30%),
    linear-gradient(128deg, #0a1322, #1e3a8a 62%, #0f172a);
}
.hero-copy h1 { margin: 1.1rem 0 1.2rem; font-family: var(--font-display); font-weight: 600; font-size: clamp(2.5rem, 5vw, 4.1rem); line-height: 1.03; letter-spacing: -.02em; }
.hero-copy h1 em { font-style: italic; color: #ecca77; }
.hero-lead { max-width: 34rem; margin: 0 0 2rem; color: #b8cfed; font-size: .98rem; }
.hero-badges { display: flex; flex-wrap: wrap; gap: .5rem; margin-top: 1.4rem; }
.hero-badges span { padding: .38rem .8rem; border: 1px solid rgba(255,255,255,.22); border-radius: 999px; font-size: .68rem; font-weight: 700; letter-spacing: .06em; color: #c0d4ee; }
.hero-actions { display: flex; flex-wrap: wrap; gap: .8rem; }

.hero-visual { position: relative; display: grid; place-items: center; min-height: 24rem; }
.book-cover {
  width: min(19rem, 88%); aspect-ratio: 3 / 4.05; padding: 1.7rem 1.6rem;
  display: flex; flex-direction: column; border-radius: 14px; color: #f4efe2;
  background:
    radial-gradient(circle at 18% 8%, rgba(233, 200, 122, .18), transparent 34%),
    linear-gradient(160deg, #162040, #0a1525 70%);
  border: 1px solid rgba(233, 200, 122, .34);
  box-shadow: var(--shadow-lg), inset 0 0 0 1px rgba(255,255,255,.03);
  transform: rotate(-2.5deg);
}
.book-cover span { width: 2.9rem; height: 2.9rem; display: grid; place-items: center; border-radius: .8rem; background: linear-gradient(140deg, #efd292, #cf9c37); color: #0c1445; font-weight: 800; }
.book-cover p { margin: 1.2rem 0 .3rem; font-size: .62rem; letter-spacing: .2em; color: #8aaccc; font-weight: 700; }
.book-cover h2 { margin: 0; font-family: var(--font-display); font-weight: 600; font-size: 1.75rem; line-height: 1.1; }
.book-cover small { margin-top: auto; font-size: .62rem; letter-spacing: .12em; color: #8aaccc; line-height: 1.5; }
.book-cover small strong { color: #ecca77; }
.hero-stat {
  position: absolute; padding: .85rem 1.1rem; border-radius: 12px;
  background: rgba(10, 20, 45, .82); border: 1px solid rgba(255,255,255,.14);
  backdrop-filter: blur(8px); box-shadow: var(--shadow-md); text-align: left;
}
.hero-stat strong { display: block; font-family: var(--font-display); font-size: 1.5rem; color: #ecca77; }
.hero-stat span { font-size: .66rem; color: #b0c8e8; letter-spacing: .04em; }
.stat-one { top: 8%; right: 2%; }
.stat-two { bottom: 10%; left: 0; }

.dashboard-wrap, .toc-section, .method-section, .cloud-tracks { padding: clamp(2.6rem, 5vw, 4.6rem) clamp(1.4rem, 5vw, 6rem); }
.dashboard-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(13rem, 1fr)); gap: 1rem; }
.progress-panel, .metric-panel {
  padding: 1.4rem 1.5rem; border-radius: var(--radius); background: var(--paper);
  border: 1px solid var(--line); box-shadow: var(--shadow-sm);
}
.progress-panel span, .metric-panel span { font-size: .63rem; font-weight: 800; letter-spacing: .13em; color: var(--muted); }
.progress-panel strong, .metric-panel strong { display: block; margin: .5rem 0 .4rem; font-family: var(--font-display); font-weight: 600; font-size: 2.1rem; color: var(--green); }
.progress-panel .progress-track { background: var(--tint); margin-bottom: .7rem; }
.progress-panel p, .metric-panel p { margin: 0; color: var(--muted); font-size: .8rem; }

.inline-search { display: inline-flex; align-items: center; gap: .55rem; padding: .62rem 1rem; border: 1px solid var(--line); border-radius: .7rem; background: var(--paper); color: var(--ink-soft); font-size: .8rem; font-weight: 600; cursor: pointer; box-shadow: var(--shadow-sm); }
.inline-search:hover { border-color: #93c5fd; color: var(--ink); }
.inline-search svg { width: .95rem; }

.chapter-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(19rem, 1fr)); gap: 1.1rem; }
.chapter-card {
  position: relative; display: flex; flex-direction: column; gap: .65rem;
  padding: 1.5rem 1.5rem 1.25rem; border-radius: var(--radius);
  background: var(--paper); border: 1px solid var(--line);
  text-decoration: none; box-shadow: var(--shadow-sm);
  transition: transform .18s ease, box-shadow .18s ease, border-color .18s ease;
  overflow: hidden;
}
.chapter-card::before { content: ""; position: absolute; inset: 0 auto 0 0; width: 4px; background: var(--acc); }
.chapter-card:hover { transform: translateY(-3px); box-shadow: var(--shadow-md); border-color: var(--line-strong); }
.card-top { display: flex; justify-content: space-between; align-items: center; }
.card-top span { font-size: .62rem; font-weight: 800; letter-spacing: .13em; color: var(--acc); }
.card-top i { padding: .22rem .6rem; border-radius: 999px; background: var(--acc-soft); color: var(--acc-ink); font-size: .62rem; font-style: normal; font-weight: 700; }
.chapter-card h2 { margin: 0; font-family: var(--font-display); font-weight: 600; font-size: 1.28rem; line-height: 1.22; letter-spacing: -.01em; }
.chapter-card p { margin: 0; color: var(--ink-soft); font-size: .82rem; flex: 1; }
.card-bottom { display: flex; align-items: center; gap: 1rem; padding-top: .7rem; border-top: 1px dashed var(--line); color: var(--muted); font-size: .72rem; }
.card-bottom strong { margin-left: auto; color: var(--acc-ink); font-size: .78rem; }
.chapter-card.done::after { content: "✓ complete"; position: absolute; top: .9rem; right: .95rem; padding: .2rem .55rem; border-radius: 999px; background: var(--green-soft); color: var(--green); font-size: .6rem; font-weight: 800; }
.chapter-card.done .card-top i { visibility: hidden; }

.method-section { background: linear-gradient(180deg, var(--canvas), #ecebe4); }
.method-intro { max-width: 42rem; margin-bottom: 2.2rem; }
.method-intro h2 { margin: .4rem 0 .8rem; font-family: var(--font-display); font-weight: 600; font-size: clamp(1.9rem, 3.4vw, 3rem); line-height: 1.06; }
.method-intro p { margin: 0; color: var(--ink-soft); }
.method-steps { display: grid; grid-template-columns: repeat(auto-fit, minmax(14rem, 1fr)); gap: 1rem; margin: 0; padding: 0; list-style: none; counter-reset: none; }
.method-steps li { display: flex; gap: 1rem; padding: 1.3rem 1.35rem; border-radius: var(--radius); background: var(--paper); border: 1px solid var(--line); box-shadow: var(--shadow-sm); }
.method-steps span { font-family: var(--font-display); font-size: 1.35rem; color: var(--gold); font-weight: 600; }
.method-steps h3 { margin: 0 0 .3rem; font-size: .95rem; }
.method-steps p { margin: 0; color: var(--muted); font-size: .8rem; }

/* Cloud tracks (AWS / GCP) on home */
.cloud-tracks-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(19rem, 1fr)); gap: 1.1rem; }
.cloud-track { padding: 1.6rem 1.6rem 1.4rem; border-radius: var(--radius); background: var(--paper); border: 1px solid var(--line); box-shadow: var(--shadow-sm); position: relative; overflow: hidden; }
.cloud-track::before { content: ""; position: absolute; inset: 0 0 auto 0; height: 4px; }
.cloud-track.aws::before { background: linear-gradient(90deg, #e58a1d, #c9720d); }
.cloud-track.gcp::before { background: linear-gradient(90deg, #4285f4, #34a853); }
.cloud-track h3 { margin: .2rem 0 .5rem; font-family: var(--font-display); font-weight: 600; font-size: 1.3rem; }
.cloud-track p { margin: 0 0 .9rem; color: var(--ink-soft); font-size: .84rem; }
.cloud-track ul { margin: 0; padding: 0; list-style: none; display: grid; gap: .4rem; }
.cloud-track li { display: flex; gap: .55rem; align-items: baseline; font-size: .8rem; color: var(--ink-soft); }
.cloud-track li::before { content: "▸"; font-size: .7rem; }
.cloud-track.aws li::before { color: var(--aws); }
.cloud-track.gcp li::before { color: var(--gcp); }
.cloud-track .track-tag { display: inline-block; margin-bottom: .6rem; padding: .24rem .65rem; border-radius: 999px; font-size: .62rem; font-weight: 800; letter-spacing: .1em; }
.cloud-track.aws .track-tag { background: var(--aws-soft); color: var(--aws); }
.cloud-track.gcp .track-tag { background: var(--gcp-soft); color: var(--gcp); }

.coverage-section { padding: clamp(2.6rem, 5vw, 4.8rem) clamp(1.4rem, 5vw, 6rem); color: #e0eeff; background: linear-gradient(140deg, #0a1322, #1e3a8a 70%, #0f172a); }
.coverage-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(13.5rem, 1fr)); gap: 1rem; margin-top: 1.6rem; }
.coverage-grid article { padding: 1.35rem 1.3rem; border: 1px solid rgba(255,255,255,.13); border-radius: var(--radius); background: rgba(255,255,255,.045); }
.coverage-grid span { font-family: var(--font-display); color: #ecca77; font-size: 1.05rem; }
.coverage-grid h3 { margin: .55rem 0 .4rem; font-size: .98rem; color: #fff; }
.coverage-grid p { margin: 0; color: #b0c8e8; font-size: .79rem; }
.source-strip { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 1rem; margin-top: 2rem; padding: 1.15rem 1.4rem; border-radius: var(--radius); background: rgba(255,255,255,.06); border: 1px solid rgba(255,255,255,.12); }
.source-strip p { margin: 0; font-size: .8rem; color: #b8cfe8; max-width: 46rem; }
.source-strip a { color: #ecca77; font-weight: 700; font-size: .8rem; text-decoration: none; }
.source-strip a:hover { text-decoration: underline; }

/* ============================================================
   Chapter page
   ============================================================ */
.reading-progress { position: sticky; top: var(--top-height); z-index: 40; height: 3px; background: transparent; }
.reading-progress i { display: block; width: 0; height: 100%; background: linear-gradient(90deg, var(--green), var(--gold)); }

.chapter-page { padding-bottom: 4rem; }
.chapter-hero {
  position: relative; padding: clamp(2.4rem, 5vw, 4rem) clamp(1.4rem, 5vw, 6rem) clamp(2.2rem, 4vw, 3.2rem);
  background:
    radial-gradient(circle at 88% 0%, color-mix(in srgb, var(--acc) 14%, transparent), transparent 42%),
    linear-gradient(180deg, var(--paper-warm), var(--canvas));
  border-bottom: 1px solid var(--line);
  overflow: hidden;
}
.chapter-hero::after {
  content: attr(data-number); position: absolute; right: clamp(.5rem, 4vw, 3rem); top: -1.4rem;
  font-family: var(--font-display); font-weight: 700; font-size: clamp(7rem, 16vw, 13rem);
  color: color-mix(in srgb, var(--acc) 9%, transparent); line-height: 1; pointer-events: none;
}
.breadcrumbs { display: flex; gap: .5rem; margin-bottom: 1.2rem; color: var(--muted); font-size: .72rem; }
.breadcrumbs a { text-decoration: none; color: var(--green); font-weight: 600; }
.breadcrumbs a:hover { text-decoration: underline; }
.chapter-eyebrow { display: flex; align-items: center; gap: .7rem; font-size: .66rem; font-weight: 800; letter-spacing: .15em; color: var(--acc); }
.chapter-eyebrow i { width: 2.2rem; height: 1px; background: var(--acc); opacity: .55; }
.chapter-hero h1 { max-width: 46rem; margin: .9rem 0 1rem; font-family: var(--font-display); font-weight: 600; font-size: clamp(2.1rem, 4.4vw, 3.6rem); line-height: 1.05; letter-spacing: -.02em; }
.chapter-hero > p { max-width: 42rem; margin: 0 0 1.4rem; color: var(--ink-soft); font-size: .95rem; }
.chapter-meta { display: flex; flex-wrap: wrap; gap: 1.2rem; align-items: center; color: var(--muted); font-size: .78rem; }
.chapter-meta span { display: inline-flex; align-items: center; gap: .45rem; }
.chapter-meta svg { width: .95rem; }
.chapter-meta button { display: inline-flex; align-items: center; gap: .45rem; padding: .5rem .85rem; border: 1px solid var(--line); border-radius: .6rem; background: var(--paper); cursor: pointer; font-size: .76rem; color: var(--ink-soft); }
.chapter-meta button:hover { border-color: var(--line-strong); color: var(--ink); }

.chapter-layout {
  display: grid; grid-template-columns: minmax(0, 1fr);
  gap: 0;
  padding: clamp(1.8rem, 4vw, 3rem) clamp(1.4rem, 5vw, 6rem) 0;
  align-items: start;
}
.chapter-rail { display: none; }
.chapter-rail { position: sticky; top: calc(var(--top-height) + 1.4rem); display: grid; gap: 1rem; }
.rail-card { padding: 1.05rem 1.1rem; border-radius: 14px; background: var(--paper); border: 1px solid var(--line); box-shadow: var(--shadow-sm); }
.rail-label { margin: 0 0 .6rem; font-size: .6rem; font-weight: 800; letter-spacing: .15em; color: var(--muted); }
.page-toc { display: grid; gap: .12rem; max-height: 44vh; overflow-y: auto; scrollbar-width: thin; }
.page-toc a { padding: .35rem .55rem; border-radius: .45rem; border-left: 2px solid transparent; color: var(--ink-soft); text-decoration: none; font-size: .74rem; line-height: 1.3; }
.page-toc a:hover { background: var(--tint); color: var(--ink); }
.page-toc a.active { border-left-color: var(--acc, var(--green)); background: var(--acc-soft, var(--green-soft)); color: var(--acc-ink, var(--green)); font-weight: 600; }
.page-toc .toc-level-3 { padding-left: 1.15rem; font-size: .7rem; }
.complete-button {
  width: 100%; display: flex; align-items: center; justify-content: center; gap: .5rem;
  padding: .68rem .8rem; border: 1px solid var(--line-strong); border-radius: .65rem;
  background: var(--paper); color: var(--ink-soft); font-weight: 700; font-size: .78rem; cursor: pointer;
}
.complete-button:hover { border-color: var(--green); color: var(--green); }
.complete-button.done { background: var(--green); border-color: var(--green); color: #fff; }
.complete-button svg { width: .95rem; }
.practice-link { display: flex; align-items: center; justify-content: center; gap: .5rem; margin-top: .6rem; padding: .55rem; border-radius: .6rem; color: var(--green); background: var(--green-soft); text-decoration: none; font-size: .76rem; font-weight: 700; }
.practice-link:hover { filter: brightness(.97); }
.practice-link svg { width: .9rem; }
.notes-card summary { display: flex; align-items: center; gap: .5rem; cursor: pointer; font-size: .8rem; font-weight: 700; color: var(--ink-soft); list-style: none; }
.notes-card summary::-webkit-details-marker { display: none; }
.notes-card svg { width: .95rem; }
.notes-card textarea { width: 100%; margin-top: .7rem; padding: .65rem .7rem; border: 1px solid var(--line); border-radius: .55rem; background: var(--paper-warm); resize: vertical; font-size: .8rem; line-height: 1.5; }
.notes-card small { display: block; margin-top: .4rem; color: var(--muted); font-size: .66rem; }

.chapter-pagination { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem; margin-top: 3.4rem; padding: 0 clamp(1.4rem, 5vw, 6rem); }
.chapter-turn { display: grid; gap: .25rem; padding: 1.15rem 1.3rem; border: 1px solid var(--line); border-radius: var(--radius); background: var(--paper); text-decoration: none; box-shadow: var(--shadow-sm); }
.chapter-turn:hover { border-color: var(--line-strong); box-shadow: var(--shadow-md); }
.chapter-turn span { color: var(--muted); font-size: .68rem; font-weight: 700; letter-spacing: .08em; }
.chapter-turn strong { font-family: var(--font-display); font-weight: 600; font-size: 1.02rem; }
.chapter-turn.next { text-align: right; }

/* ============================================================
   Chapter content typography
   ============================================================ */
.chapter-content { max-width: none; min-width: 0; font-size: calc(var(--reader-size) * .97); }
.chapter-content > section { margin-bottom: 2.6rem; }
.chapter-content h2 {
  margin: 0 0 .9rem; padding-bottom: .55rem; border-bottom: 1px solid var(--line);
  font-family: var(--font-display); font-weight: 600; font-size: 1.72rem; line-height: 1.16; letter-spacing: -.015em;
}
.chapter-content h3 { margin: 1.7rem 0 .55rem; font-size: 1.06rem; font-weight: 700; }
.chapter-content h4 { margin: 1.3rem 0 .4rem; font-size: .92rem; font-weight: 700; color: var(--ink-soft); }
.chapter-content p { margin: 0 0 1rem; color: #1e293b; }
.chapter-content ul, .chapter-content ol { margin: 0 0 1.1rem; padding-left: 1.35rem; color: #1e293b; }
.chapter-content li { margin-bottom: .4rem; }
.chapter-content li::marker { color: var(--acc, var(--green)); font-weight: 700; }
.chapter-content a { color: var(--green); text-decoration: underline; text-decoration-color: #93c5fd; text-underline-offset: 3px; }
.chapter-content a:hover { text-decoration-color: var(--green); }
.chapter-content strong { color: var(--ink); }

.chapter-content code { font-family: var(--font-mono); font-size: .82em; background: var(--tint); border: 1px solid var(--line); border-radius: .3rem; padding: .1rem .32rem; }
.chapter-content pre {
  margin: 0 0 1.2rem; padding: 1.05rem 1.15rem; overflow-x: auto;
  border-radius: var(--radius-sm); border: 1px solid #1e2d4a;
  background: #0f1e3d; color: #d0ddf8;
  font-size: .8rem; line-height: 1.6; position: relative;
  scrollbar-width: thin;
}
.chapter-content pre code { background: transparent; border: 0; padding: 0; color: inherit; font-size: 1em; }
.copy-code {
  position: absolute; top: .5rem; right: .5rem; padding: .28rem .6rem;
  border: 1px solid rgba(255,255,255,.18); border-radius: .4rem;
  background: rgba(255,255,255,.06); color: #b9cfc5; font-size: .64rem; font-weight: 700; cursor: pointer;
  opacity: 0; transition: opacity .15s ease;
}
.chapter-content pre:hover .copy-code, .copy-code:focus-visible { opacity: 1; }
.copy-code:hover { background: rgba(255,255,255,.14); color: #fff; }

.chapter-content table {
  width: 100%; margin: 0 0 1.3rem; border-collapse: separate; border-spacing: 0;
  font-size: .82rem; background: var(--paper); border: 1px solid var(--line);
  border-radius: var(--radius-sm); overflow: hidden; box-shadow: var(--shadow-sm);
}
.chapter-content thead th {
  text-align: left; padding: .68rem .85rem; background: var(--acc-soft, var(--green-soft));
  color: var(--acc-ink, var(--green)); font-size: .7rem; letter-spacing: .06em; text-transform: uppercase;
  border-bottom: 1px solid var(--line);
}
.chapter-content tbody td { padding: .62rem .85rem; border-bottom: 1px solid var(--line); vertical-align: top; color: #1e293b; }
.chapter-content tbody tr:last-child td { border-bottom: 0; }
.chapter-content tbody tr:nth-child(even) { background: var(--paper-warm); }
.table-scroll { overflow-x: auto; margin-bottom: 1.3rem; }
.table-scroll table { margin-bottom: 0; }

.chapter-content blockquote { margin: 0 0 1.1rem; padding: .8rem 1.15rem; border-left: 3px solid var(--gold); background: var(--gold-soft); border-radius: 0 var(--radius-sm) var(--radius-sm) 0; color: #4d4432; font-size: .9rem; }

/* Learning objectives */
.learning-path {
  margin-bottom: 2.6rem; padding: 1.45rem 1.6rem; border-radius: var(--radius);
  background: linear-gradient(135deg, var(--acc-soft, var(--green-soft)), color-mix(in srgb, var(--acc-soft, var(--green-soft)) 45%, #fff));
  border: 1px solid color-mix(in srgb, var(--acc, var(--green)) 24%, var(--line));
}
.learning-path h2 { margin: 0 0 .6rem; border: 0; padding: 0; font-size: 1.1rem; font-family: var(--font-body); font-weight: 800; letter-spacing: .01em; color: var(--acc-ink, var(--green)); text-transform: uppercase; font-size: .82rem; }
.learning-path p { margin: 0 0 .6rem; font-size: .88rem; }
.learning-path ul { margin: 0; padding: 0; list-style: none; display: grid; gap: .45rem; }
.learning-path li { position: relative; padding-left: 1.55rem; font-size: .87rem; }
.learning-path li::before {
  content: ""; position: absolute; left: 0; top: .32em; width: .95rem; height: .95rem;
  border-radius: 50%; background: var(--acc, var(--green));
  mask: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='black' stroke-width='3' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='m5 12 4 4L19 6'/%3E%3C/svg%3E") center/contain no-repeat;
}

/* Callouts */
.callout {
  display: grid; gap: .3rem; margin: 0 0 1.2rem; padding: 1rem 1.2rem 1.05rem 1.35rem;
  border-radius: var(--radius-sm); border: 1px solid; border-left-width: 4px;
  font-size: .87rem; background: var(--paper);
}
.callout > strong { font-size: .7rem; font-weight: 800; letter-spacing: .12em; text-transform: uppercase; }
.callout p { margin: 0 !important; }
.callout.signal { border-color: #bfcfe8; border-left-color: var(--green); background: #eff6ff; }
.callout.signal > strong { color: var(--green); }
.callout.warning { border-color: #ecc9c9; border-left-color: #b3413f; background: #fbf1f0; }
.callout.warning > strong { color: #a03b39; }
.callout.example { border-color: #e2d7bb; border-left-color: var(--gold); background: #fbf6e8; }
.callout.example > strong { color: #8a6b1f; }
.callout.aws { border-color: #eed7b7; border-left-color: var(--aws); background: var(--aws-soft); }
.callout.aws > strong { color: var(--aws); }
.callout.gcp { border-color: #c8d9f6; border-left-color: var(--gcp); background: var(--gcp-soft); }
.callout.gcp > strong { color: var(--gcp); }

/* Decision grid */
.decision-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(13rem, 1fr)); gap: .9rem; margin: 0 0 1.3rem; }
.decision-grid article { padding: 1.05rem 1.1rem; border-radius: var(--radius-sm); background: var(--paper); border: 1px solid var(--line); border-top: 3px solid var(--acc, var(--green)); box-shadow: var(--shadow-sm); }
.decision-grid h3 { margin: 0 0 .4rem !important; font-size: .9rem !important; }
.decision-grid p { margin: 0 !important; font-size: .8rem; color: var(--ink-soft) !important; }

/* Legacy ASCII diagram */
.diagram { margin: 0 0 1.3rem; padding: 1.1rem 1.2rem; border-radius: var(--radius-sm); border: 1px dashed var(--line-strong); background: var(--paper-warm); overflow-x: auto; }
.diagram code { display: block; background: transparent; border: 0; padding: 0; font-family: var(--font-mono); font-size: .74rem; line-height: 1.55; white-space: pre; color: var(--ink-soft); }

/* ---------- Mermaid diagram card ---------- */
.diagram-card {
  margin: 0 0 1.4rem; padding: 0; border-radius: var(--radius);
  border: 1px solid var(--line); background: var(--paper);
  box-shadow: var(--shadow-sm); overflow: hidden;
}
.diagram-card figcaption {
  display: flex; align-items: center; gap: .6rem; padding: .68rem 1.1rem;
  border-bottom: 1px solid var(--line); background: var(--paper-warm);
  font-size: .76rem; font-weight: 600; color: var(--ink-soft);
}
.fig-label {
  flex: none; padding: .16rem .55rem; border-radius: 999px;
  background: var(--acc-soft, var(--green-soft)); color: var(--acc-ink, var(--green));
  font-size: .62rem; font-weight: 800; letter-spacing: .08em; text-transform: uppercase;
}
.diagram-card .mermaid {
  display: flex; justify-content: center; margin: 0; padding: 1.15rem 1rem;
  background: var(--paper); border: 0; color: var(--ink-soft);
  overflow-x: auto; font-family: var(--font-mono); font-size: .74rem; line-height: 1.5;
}
html.js .diagram-card .mermaid:not([data-processed]) { visibility: hidden; min-height: 3rem; }
.diagram-card .mermaid:not([data-processed]), .diagram-card .mermaid.mermaid-error { white-space: pre; justify-content: flex-start; }
.diagram-card .mermaid.mermaid-error { visibility: visible; }
.diagram-card .mermaid svg { max-width: 100%; height: auto; }

/* ---------- Flow row (CSS block diagram) ---------- */
.flow-row { display: flex; flex-wrap: wrap; align-items: center; gap: .55rem; margin: 0 0 1.3rem; }
.flow-node {
  padding: .55rem .95rem; border-radius: .65rem; background: var(--paper);
  border: 1px solid var(--line-strong); box-shadow: var(--shadow-sm);
  font-size: .78rem; font-weight: 600; color: var(--ink-soft); text-align: center;
}
.flow-node.emphasis { background: var(--acc, var(--green)); border-color: var(--acc, var(--green)); color: #fff; }
.flow-node:not(:last-child)::after { content: "→"; margin-left: .55rem; margin-right: -.1rem; color: var(--acc, var(--green)); font-weight: 700; display: inline-block; transform: translateX(.5rem); }
.flow-node:not(:last-child) { margin-right: .8rem; }

/* ---------- Layer stack ---------- */
.layer-stack { display: grid; gap: .45rem; margin: 0 0 1.3rem; }
.layer-stack .layer {
  display: grid; grid-template-columns: 11rem 1fr; gap: .4rem; align-items: center;
  padding: .8rem 1.1rem; border-radius: var(--radius-sm);
  background: linear-gradient(90deg, var(--acc-soft, var(--green-soft)), var(--paper));
  border: 1px solid var(--line); border-left: 4px solid var(--acc, var(--green));
}
.layer-stack .layer strong { font-size: .84rem; }
.layer-stack .layer span { color: var(--muted); font-size: .78rem; }
.layer-stack .layer.base { background: var(--forest); border-color: var(--forest); color: #d0def8; }
.layer-stack .layer.base strong { color: #ecca77; }
.layer-stack .layer.base span { color: #8aaccc; }

/* ---------- Cloud map (AWS vs GCP) ---------- */
.cloud-map { display: grid; grid-template-columns: repeat(auto-fit, minmax(15rem, 1fr)); gap: .9rem; margin: 0 0 1.3rem; }
.cloud-col { border-radius: var(--radius-sm); border: 1px solid var(--line); background: var(--paper); overflow: hidden; box-shadow: var(--shadow-sm); }
.cloud-col h4 { margin: 0; padding: .6rem 1rem; font-size: .74rem; font-weight: 800; letter-spacing: .1em; text-transform: uppercase; }
.cloud-col.aws h4 { background: var(--aws-soft); color: var(--aws); border-bottom: 2px solid var(--aws); }
.cloud-col.gcp h4 { background: var(--gcp-soft); color: var(--gcp); border-bottom: 2px solid var(--gcp); }
.cloud-col ul { margin: 0; padding: .5rem 0; list-style: none; }
.cloud-col li { display: grid; gap: .06rem; padding: .5rem 1rem; font-size: .8rem; }
.cloud-col li + li { border-top: 1px dashed var(--line); }
.cloud-col li strong { font-size: .82rem; }
.cloud-col li span { color: var(--muted); font-size: .74rem; }

/* ---------- Stat strip ---------- */
.stat-strip { display: grid; grid-template-columns: repeat(auto-fit, minmax(10.5rem, 1fr)); gap: .9rem; margin: 0 0 1.3rem; }
.stat-strip > div {
  padding: 1.05rem 1.15rem; border-radius: var(--radius-sm); text-align: left;
  background: linear-gradient(160deg, var(--acc-soft, var(--green-soft)), #fff 90%);
  border: 1px solid color-mix(in srgb, var(--acc, var(--green)) 22%, var(--line));
}
.stat-strip strong { display: block; font-family: var(--font-display); font-weight: 600; font-size: 1.55rem; line-height: 1.1; color: var(--acc-ink, var(--green)); }
.stat-strip span { display: block; margin-top: .3rem; color: var(--ink-soft); font-size: .74rem; line-height: 1.4; }

/* ---------- Icon list ---------- */
.icon-list { margin: 0 0 1.3rem !important; padding: 0 !important; list-style: none !important; display: grid; gap: .55rem; }
.icon-list li { position: relative; margin: 0 !important; padding: .7rem .9rem .7rem 2.9rem; border-radius: var(--radius-sm); background: var(--paper); border: 1px solid var(--line); font-size: .84rem; color: var(--ink-soft); }
.icon-list li strong { color: var(--ink); }
.icon-list li::before {
  content: ""; position: absolute; left: .8rem; top: .78rem; width: 1.35rem; height: 1.35rem;
  border-radius: .42rem; background: var(--acc-soft, var(--green-soft));
}
.icon-list li::after {
  content: ""; position: absolute; left: 1.02rem; top: 1rem; width: .92rem; height: .92rem;
  background-color: var(--acc-ink, var(--green));
  mask: var(--icon, url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='black' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='m5 12 4 4L19 6'/%3E%3C/svg%3E")) center/contain no-repeat;
}
.icon-list li[data-icon="check"]::after   { --icon: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='black' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='m5 12 4 4L19 6'/%3E%3C/svg%3E"); }
.icon-list li[data-icon="warn"]::after    { --icon: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='black' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M12 3 2 21h20L12 3z'/%3E%3Cpath d='M12 10v5m0 3h.01'/%3E%3C/svg%3E"); }
.icon-list li[data-icon="bolt"]::after    { --icon: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='black' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M13 2 4 14h6l-1 8 9-12h-6l1-8z'/%3E%3C/svg%3E"); }
.icon-list li[data-icon="shield"]::after  { --icon: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='black' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M12 2 4 5v6c0 5 3.4 9.4 8 11 4.6-1.6 8-6 8-11V5l-8-3z'/%3E%3C/svg%3E"); }
.icon-list li[data-icon="db"]::after      { --icon: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='black' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cellipse cx='12' cy='5' rx='8' ry='3'/%3E%3Cpath d='M4 5v14c0 1.7 3.6 3 8 3s8-1.3 8-3V5'/%3E%3Cpath d='M4 12c0 1.7 3.6 3 8 3s8-1.3 8-3'/%3E%3C/svg%3E"); }
.icon-list li[data-icon="cloud"]::after   { --icon: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='black' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M7 18a5 5 0 1 1 1-9.9A6 6 0 0 1 19.7 10 4 4 0 0 1 18 18H7z'/%3E%3C/svg%3E"); }
.icon-list li[data-icon="gear"]::after    { --icon: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='black' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Ccircle cx='12' cy='12' r='3'/%3E%3Cpath d='M12 2v3m0 14v3M4.9 4.9l2.1 2.1m10 10 2.1 2.1M2 12h3m14 0h3M4.9 19.1 7 17m10-10 2.1-2.1'/%3E%3C/svg%3E"); }
.icon-list li[data-icon="chart"]::after   { --icon: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='black' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M4 20v-6m5 6V8m5 12v-9m5 9V5'/%3E%3C/svg%3E"); }
.icon-list li[data-icon="dollar"]::after  { --icon: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='black' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M12 2v20'/%3E%3Cpath d='M17 6.5c-1-1.5-2.7-2-5-2-2.8 0-5 1.2-5 3.5C7 12 17 11 17 15c0 2.3-2.2 3.5-5 3.5-2.3 0-4-.5-5-2'/%3E%3C/svg%3E"); }
.icon-list li[data-icon="clock"]::after   { --icon: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='black' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Ccircle cx='12' cy='12' r='9'/%3E%3Cpath d='M12 7v5l3 3'/%3E%3C/svg%3E"); }
.icon-list li[data-icon="lock"]::after    { --icon: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='black' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Crect x='4' y='11' width='16' height='10' rx='2'/%3E%3Cpath d='M8 11V7a4 4 0 0 1 8 0v4'/%3E%3C/svg%3E"); }
.icon-list li[data-icon="network"]::after { --icon: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='black' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Ccircle cx='12' cy='5' r='2.5'/%3E%3Ccircle cx='5' cy='19' r='2.5'/%3E%3Ccircle cx='19' cy='19' r='2.5'/%3E%3Cpath d='M10.8 7 6 16.7M13.2 7 18 16.7M7.5 19h9'/%3E%3C/svg%3E"); }
.icon-list li[data-icon="brain"]::after   { --icon: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='black' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M12 3a5 4.5 0 0 0-5 4.5c-1.8.6-3 2.2-3 4a4.3 4.3 0 0 0 3 4c.4 2 2.4 3.5 5 3.5s4.6-1.5 5-3.5a4.3 4.3 0 0 0 3-4c0-1.8-1.2-3.4-3-4A5 4.5 0 0 0 12 3z'/%3E%3Cpath d='M12 3v16'/%3E%3C/svg%3E"); }
.icon-list li[data-icon="layers"]::after  { --icon: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='black' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='m12 2 10 5-10 5L2 7l10-5z'/%3E%3Cpath d='m2 12 10 5 10-5M2 17l10 5 10-5'/%3E%3C/svg%3E"); }
.icon-list li[data-icon="flag"]::after    { --icon: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='black' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M5 3v18'/%3E%3Cpath d='M5 4h12l-2 4 2 4H5'/%3E%3C/svg%3E"); }
.icon-list li[data-icon="eye"]::after     { --icon: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='black' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M2 12s3.5-7 10-7 10 7 10 7-3.5 7-10 7S2 12 2 12z'/%3E%3Ccircle cx='12' cy='12' r='3'/%3E%3C/svg%3E"); }

/* ---------- Timeline ---------- */
.timeline { margin: 0 0 1.3rem !important; padding: 0 !important; list-style: none !important; display: grid; gap: 0; counter-reset: tl; }
.timeline li { position: relative; margin: 0 !important; padding: 0 0 1.15rem 2.9rem; counter-increment: tl; }
.timeline li::before {
  content: counter(tl, decimal-leading-zero); position: absolute; left: 0; top: 0;
  width: 1.9rem; height: 1.9rem; display: grid; place-items: center;
  border-radius: 50%; background: var(--acc-soft, var(--green-soft));
  border: 1px solid color-mix(in srgb, var(--acc, var(--green)) 40%, transparent);
  color: var(--acc-ink, var(--green)); font-size: .66rem; font-weight: 800;
}
.timeline li::after { content: ""; position: absolute; left: .93rem; top: 2.1rem; bottom: .2rem; width: 2px; background: var(--line); }
.timeline li:last-child::after { display: none; }
.timeline li:last-child { padding-bottom: .2rem; }
.timeline strong { display: block; font-size: .9rem; margin-bottom: .12rem; }
.timeline span { display: block; color: var(--ink-soft); font-size: .82rem; }

/* ---------- Term grid (glossary) ---------- */
.term-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(14rem, 1fr)); gap: .7rem; margin: 0 0 1.3rem; }
.term-grid > div { padding: .8rem .95rem; border-radius: var(--radius-sm); background: var(--paper); border: 1px solid var(--line); }
.term-grid dt { font-weight: 800; font-size: .78rem; color: var(--acc-ink, var(--green)); letter-spacing: .02em; }
.term-grid dd { margin: .25rem 0 0; color: var(--ink-soft); font-size: .78rem; line-height: 1.5; }

/* ---------- Q&A cards ---------- */
.qa-card { margin-bottom: .8rem; border: 1px solid var(--line); border-radius: var(--radius-sm); background: var(--paper); box-shadow: var(--shadow-sm); overflow: hidden; }
.qa-card[open] { border-color: color-mix(in srgb, var(--acc, var(--green)) 38%, var(--line)); box-shadow: var(--shadow-md); }
.qa-card summary { display: flex; gap: .8rem; align-items: baseline; padding: .95rem 1.1rem; cursor: pointer; font-weight: 600; font-size: .9rem; list-style: none; }
.qa-card summary::-webkit-details-marker { display: none; }
.qa-card summary:hover { background: var(--paper-warm); }
.q-number { flex: none; padding: .18rem .55rem; border-radius: .45rem; background: var(--acc-soft, var(--green-soft)); color: var(--acc-ink, var(--green)); font-size: .68rem; font-weight: 800; }
.qa-answer { padding: .35rem 1.2rem 1.2rem; border-top: 1px dashed var(--line); font-size: .86rem; }
.qa-answer h3 { margin: .95rem 0 .45rem !important; font-size: .76rem !important; font-weight: 800; letter-spacing: .1em; text-transform: uppercase; color: var(--muted); }
.qa-answer ol, .qa-answer ul { margin-bottom: .6rem; }
.rubric { margin-top: .9rem; padding: .75rem .95rem; border-radius: var(--radius-sm); background: var(--gold-soft); border: 1px solid #e5d5ab; font-size: .8rem; }
.rubric strong { display: block; margin-bottom: .2rem; font-size: .66rem; font-weight: 800; letter-spacing: .12em; text-transform: uppercase; color: #8a6b1f; }
.rubric p { margin: 0 !important; }

/* References */
.references { margin-top: 2.4rem; padding: 1.2rem 1.3rem; border-radius: var(--radius-sm); background: var(--paper-warm); border: 1px solid var(--line); font-size: .78rem; color: var(--ink-soft); }
.references p { margin: 0 0 .5rem; }
.references ul { margin: 0; padding-left: 1.2rem; }
.references li { margin-bottom: .3rem; }

/* ============================================================
   Complete printable edition
   ============================================================ */
.complete-book { padding-bottom: 4rem; }
.complete-cover {
  min-height: 30rem; display: flex; flex-direction: column; align-items: flex-start; justify-content: center; gap: 1rem;
  padding: clamp(3rem, 7vw, 6rem) clamp(1.6rem, 6vw, 7rem); color: #fff;
  background:
    radial-gradient(circle at 80% 12%, rgba(59, 130, 246, .18), transparent 30%),
    linear-gradient(130deg, #0a1322, #1e3a8a 65%, #0f172a);
}
.complete-cover h1 { margin: 0; font-family: var(--font-display); font-weight: 600; font-size: clamp(2.6rem, 6vw, 4.6rem); line-height: 1.03; letter-spacing: -.02em; }
.complete-cover p { max-width: 40rem; margin: 0; color: #b8cfe8; }
.complete-cover strong { letter-spacing: .14em; font-size: .74rem; color: #ecca77; }
.complete-cover button { margin-top: .6rem; display: inline-flex; align-items: center; gap: .6rem; padding: .7rem 1.15rem; border: 0; border-radius: .72rem; background: var(--gold); color: #1a1f1a; font-weight: 700; cursor: pointer; }
.complete-toc { padding: clamp(2.4rem, 5vw, 4rem) clamp(1.6rem, 6vw, 7rem); }
.complete-toc h2 { margin: .4rem 0 1.4rem; font-family: var(--font-display); font-weight: 600; font-size: clamp(1.8rem, 3.4vw, 2.8rem); }
.complete-toc > div { display: grid; grid-template-columns: repeat(auto-fill, minmax(19rem, 1fr)); gap: .7rem; }
.complete-toc a { display: grid; grid-template-columns: 2.2rem 1fr; gap: .3rem .7rem; align-items: baseline; padding: .85rem 1rem; border: 1px solid var(--line); border-radius: var(--radius-sm); background: var(--paper); text-decoration: none; box-shadow: var(--shadow-sm); }
.complete-toc a:hover { border-color: var(--line-strong); box-shadow: var(--shadow-md); }
.complete-toc a span { font-family: var(--font-display); color: var(--gold); font-weight: 600; }
.complete-toc a strong { font-size: .9rem; line-height: 1.3; }
.complete-toc a small { grid-column: 2; color: var(--muted); font-size: .7rem; }
.complete-chapter { padding: 0 clamp(1.6rem, 6vw, 7rem); margin-bottom: 3.4rem; }
.complete-chapter-head { margin-bottom: 1.8rem; padding: 1.6rem 1.8rem; border-radius: var(--radius); background: linear-gradient(135deg, var(--acc-soft), color-mix(in srgb, var(--acc-soft) 40%, #fff)); border: 1px solid color-mix(in srgb, var(--acc) 24%, var(--line)); }
.complete-chapter-head p { margin: 0; font-size: .66rem; font-weight: 800; letter-spacing: .14em; color: var(--acc); }
.complete-chapter-head h2 { margin: .4rem 0; font-family: var(--font-display); font-weight: 600; font-size: clamp(1.7rem, 3vw, 2.5rem); line-height: 1.1; }
.complete-chapter-head span { color: var(--muted); font-size: .78rem; }
.complete-chapter .chapter-content { max-width: 50rem; }

/* ============================================================
   Practice studio
   ============================================================ */
.practice-hero { padding: clamp(2.8rem, 6vw, 5rem) clamp(1.4rem, 5vw, 6rem) 1.4rem; }
.practice-hero h1 { margin: .8rem 0; font-family: var(--font-display); font-weight: 600; font-size: clamp(2.2rem, 4.6vw, 3.6rem); letter-spacing: -.02em; }
.practice-hero p { max-width: 46rem; margin: 0; color: var(--ink-soft); }
.studio { display: grid; grid-template-columns: minmax(0, 1fr) 12rem; gap: 1.2rem; padding: 1.6rem clamp(1.4rem, 5vw, 6rem); align-items: start; }
.studio-controls { grid-column: 1 / -1; display: flex; flex-wrap: wrap; gap: .9rem; align-items: flex-end; padding: 1.1rem 1.2rem; border-radius: var(--radius); background: var(--paper); border: 1px solid var(--line); box-shadow: var(--shadow-sm); }
.studio-controls label { display: grid; gap: .3rem; font-size: .68rem; font-weight: 800; letter-spacing: .1em; color: var(--muted); }
.studio-controls select { min-width: 11rem; padding: .55rem .6rem; border: 1px solid var(--line-strong); border-radius: .55rem; background: var(--paper); font-size: .82rem; font-weight: 500; letter-spacing: 0; }
.studio-controls .primary-action { margin-left: auto; }
.practice-stage { min-height: 21rem; border-radius: var(--radius); background: var(--paper); border: 1px solid var(--line); box-shadow: var(--shadow-sm); }
.practice-empty { display: grid; place-items: center; gap: .5rem; min-height: 21rem; padding: 2rem; text-align: center; color: var(--muted); }
.practice-empty svg { width: 2rem; height: 2rem; color: var(--green); }
.practice-empty h2 { margin: 0; font-family: var(--font-display); font-weight: 600; font-size: 1.4rem; color: var(--ink); }
.practice-empty p { margin: 0; max-width: 26rem; font-size: .84rem; }
.practice-question { padding: 1.5rem 1.7rem; }
.practice-question-head { display: flex; flex-wrap: wrap; gap: .8rem; justify-content: space-between; margin-bottom: 1rem; color: var(--muted); font-size: .68rem; font-weight: 800; letter-spacing: .08em; }
.practice-timer { color: var(--green); }
.practice-question h2 { margin: 0 0 1.2rem; font-family: var(--font-display); font-weight: 600; font-size: 1.45rem; line-height: 1.3; }
.practice-answer { margin-bottom: 1.2rem; padding: 1rem 1.2rem; border-radius: var(--radius-sm); background: var(--green-soft); border: 1px solid #93c5fd; font-size: .86rem; }
.practice-answer strong { display: block; margin-bottom: .4rem; font-size: .68rem; font-weight: 800; letter-spacing: .12em; text-transform: uppercase; color: var(--green); }
.practice-answer p { margin: 0; }
.practice-actions { display: flex; flex-wrap: wrap; gap: .55rem; }
.practice-actions button { padding: .58rem .95rem; border: 1px solid var(--line-strong); border-radius: .6rem; background: var(--paper); font-size: .78rem; font-weight: 600; cursor: pointer; color: var(--ink-soft); }
.practice-actions button:hover { border-color: var(--green); color: var(--green); }
.practice-actions button.primary { background: var(--green); border-color: var(--green); color: #fff; }
.practice-actions button.primary:hover { background: #1e40af; color: #fff; }
.practice-score { display: grid; gap: .7rem; }
.practice-score > div { padding: 1rem 1.1rem; border-radius: var(--radius-sm); background: var(--paper); border: 1px solid var(--line); box-shadow: var(--shadow-sm); }
.practice-score span { font-size: .62rem; font-weight: 800; letter-spacing: .13em; color: var(--muted); }
.practice-score strong { display: block; font-family: var(--font-display); font-weight: 600; font-size: 1.7rem; color: var(--green); }
.answer-framework { margin: 1rem clamp(1.4rem, 5vw, 6rem) 3.5rem; padding: 1.8rem 1.9rem; border-radius: var(--radius); background: var(--paper); border: 1px solid var(--line); box-shadow: var(--shadow-sm); }
.answer-framework h2 { margin: .3rem 0 1.2rem; font-family: var(--font-display); font-weight: 600; font-size: 1.6rem; }
.answer-framework ol { display: grid; gap: .6rem; margin: 0; padding: 0; list-style: none; }
.answer-framework li { display: flex; gap: .9rem; align-items: baseline; }
.answer-framework b { flex: none; width: 1.7rem; height: 1.7rem; display: grid; place-items: center; border-radius: .5rem; background: var(--green-soft); color: var(--green); font-size: .8rem; }
.answer-framework span { font-size: .86rem; color: var(--ink-soft); }
.noscript-note { margin: 0 clamp(1.4rem, 5vw, 6rem) 2rem; padding: 1rem; border-radius: var(--radius-sm); background: var(--gold-soft); font-size: .84rem; }

/* ============================================================
   Search dialog
   ============================================================ */
.search-dialog { width: min(44rem, calc(100vw - 2rem)); margin: 8vh auto auto; padding: 0; border: 0; border-radius: var(--radius); background: transparent; }
.search-dialog::backdrop { background: rgba(10, 20, 45, .45); backdrop-filter: blur(3px); }
.search-panel { border-radius: var(--radius); background: var(--paper); border: 1px solid var(--line); box-shadow: var(--shadow-lg); overflow: hidden; }
.search-box { display: flex; align-items: center; gap: .7rem; padding: .95rem 1.15rem; border-bottom: 1px solid var(--line); }
.search-box svg { width: 1.05rem; color: var(--muted); }
.search-box input { flex: 1; border: 0; outline: none; background: transparent; font-size: .95rem; }
.search-box button { padding: .3rem .6rem; border: 1px solid var(--line-strong); border-radius: .4rem; background: var(--paper-warm); color: var(--muted); font-size: .66rem; font-weight: 700; cursor: pointer; }
.search-intro { display: grid; gap: .1rem; padding: .8rem 1.2rem; background: var(--paper-warm); border-bottom: 1px solid var(--line); }
.search-intro strong { font-size: .78rem; }
.search-intro span { color: var(--muted); font-size: .7rem; }
.search-results { max-height: 52vh; overflow-y: auto; scrollbar-width: thin; }
.search-empty { padding: 1.6rem 1.3rem; color: var(--muted); font-size: .84rem; }
.search-result { display: grid; grid-template-columns: 2.2rem 1fr; gap: .85rem; padding: .9rem 1.15rem; text-decoration: none; border-bottom: 1px solid var(--line); }
.search-result:hover, .search-result:focus-visible { background: var(--green-soft); }
.search-result > span { height: 1.65rem; display: grid; place-items: center; border-radius: .45rem; background: var(--tint); color: var(--ink-soft); font-size: .68rem; font-weight: 800; }
.search-result strong { display: block; font-size: .85rem; }
.search-result small { color: var(--green); font-size: .68rem; font-weight: 700; }
.search-result p { margin: .25rem 0 0; color: var(--muted); font-size: .76rem; line-height: 1.5; }
.search-result mark { background: #f3e3b3; color: inherit; border-radius: 2px; padding: 0 1px; }

/* ============================================================
   Utilities
   ============================================================ */
.back-to-top {
  position: fixed; right: 1.3rem; bottom: 1.3rem; z-index: 50;
  width: 2.7rem; height: 2.7rem; border: 1px solid var(--line-strong); border-radius: 50%;
  background: var(--paper); color: var(--ink-soft); font-size: 1.1rem; cursor: pointer;
  box-shadow: var(--shadow-md); opacity: 0; pointer-events: none; transform: translateY(8px);
  transition: opacity .2s ease, transform .2s ease;
}
.back-to-top.show { opacity: 1; pointer-events: auto; transform: none; }
.back-to-top:hover { color: var(--green); border-color: var(--green); }

.toast {
  position: fixed; left: 50%; bottom: 1.4rem; z-index: 90; transform: translate(-50%, 12px);
  max-width: min(26rem, 90vw); padding: .7rem 1.15rem; border-radius: .7rem;
  background: var(--forest); color: #e0eeff; font-size: .8rem; font-weight: 600;
  opacity: 0; pointer-events: none; transition: opacity .2s ease, transform .2s ease;
  box-shadow: var(--shadow-lg);
}
.toast.show { opacity: 1; transform: translate(-50%, 0); }

.site-footer { padding: 1.8rem clamp(1.4rem, 5vw, 6rem); border-top: 1px solid var(--line); color: var(--muted); font-size: .74rem; }
.site-footer p { margin: .2rem 0; }
.site-footer a { color: var(--green); }

/* ============================================================
   Desktop sidebar collapse
   ============================================================ */
.nav-collapse-toggle { display: none !important; }

@media (min-width: 981px) {
  .nav-collapse-toggle { display: grid !important; }
  .site-nav { transition: transform .28s cubic-bezier(.4, 0, .2, 1); }
  .page-shell { transition: margin-left .28s cubic-bezier(.4, 0, .2, 1), width .28s cubic-bezier(.4, 0, .2, 1); }
  body.nav-collapsed .site-nav { transform: translateX(-100%); }
  body.nav-collapsed .page-shell { width: 100%; margin-left: 0; }
}

/* ============================================================
   Responsive
   ============================================================ */
@media (max-width: 1180px) {
  .chapter-layout { grid-template-columns: minmax(0, 1fr); }
}

@media (max-width: 980px) {
  .page-shell { width: 100%; margin-left: 0; }
  .site-nav { transform: translateX(-102%); transition: transform .25s ease; width: min(20rem, 86vw); box-shadow: var(--shadow-lg); }
  body.nav-open .site-nav { transform: none; }
  body.nav-open .nav-scrim { display: block; position: fixed; inset: 0; z-index: 55; background: rgba(10, 20, 45, .4); }
  .nav-close { display: block; }
  .menu-button { display: grid !important; }
  .mobile-title { display: block; }
  .search-trigger { width: auto; flex: 1; }
  .search-trigger span { display: none; }
  .search-trigger kbd { display: none; }
  .home-hero { grid-template-columns: 1fr; min-height: 0; }
  .hero-visual { display: none; }
  .studio { grid-template-columns: 1fr; }
  .practice-score { grid-template-columns: repeat(3, 1fr); }
  .chapter-pagination { grid-template-columns: 1fr; }
  .layer-stack .layer { grid-template-columns: 1fr; gap: .1rem; }
}

@media (max-width: 560px) {
  .chapter-hero::after { display: none; }
  .stat-strip { grid-template-columns: 1fr 1fr; }
  .flow-row { flex-direction: column; align-items: stretch; }
  .flow-node { text-align: center; }
  .flow-node:not(:last-child) { margin-right: 0; }
  .flow-node:not(:last-child)::after { content: "↓"; display: block; margin: .4rem 0 -.2rem; transform: none; }
  .method-steps { grid-template-columns: 1fr; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation: none !important; transition: none !important; }
}

/* ============================================================
   Print
   ============================================================ */
@media print {
  :root { --reader-size: 10.5pt; }
  body { background: #fff; }
  .site-nav, .topbar, .nav-scrim, .back-to-top, .toast, .search-dialog,
  .chapter-rail, .reading-progress, .chapter-meta button, .skip-link,
  .chapter-pagination, .breadcrumbs, .copy-code, .complete-cover button { display: none !important; }
  .page-shell { width: 100%; margin: 0; }
  .chapter-layout, .chapter-hero, .complete-chapter, .complete-toc { padding-left: 0; padding-right: 0; }
  .chapter-content { max-width: none; }
  .chapter-hero { background: #fff; border-bottom: 2px solid #000; }
  .chapter-hero::after { display: none; }
  a { text-decoration: none; }
  .qa-card, .diagram-card, .callout, .decision-grid article, .stat-strip > div, .timeline li { break-inside: avoid; }
  .qa-card { box-shadow: none; }
  .chapter-content pre { background: #f4f4f4; color: #222; border-color: #ccc; }
  .diagram-card .mermaid { visibility: visible !important; }
  .complete-chapter { page-break-before: always; }
  .site-footer { border: 0; }
}