:root {
  --bg: #f4f0e8;
  --paper: #fbf8f2;
  --paper-strong: #f0e8db;
  --ink: #1e2420;
  --muted: #5d645d;
  --line: rgba(30, 36, 32, 0.14);
  --accent: #0f6a52;
  --accent-soft: #dcefe8;
  --contrast: #1f2b29;
  --contrast-2: #dfe7e2;
  --shadow: 0 24px 60px rgba(28, 33, 31, 0.08);
  --radius: 22px;
  --radius-sm: 14px;
  --space-1: 0.5rem;
  --space-2: 0.75rem;
  --space-3: 1rem;
  --space-4: 1.5rem;
  --space-5: 2rem;
  --space-6: 3rem;
  --space-7: 4.5rem;
  --space-8: 6rem;
  --font-display: "Instrument Serif", serif;
  --font-body: "Manrope", sans-serif;
  --font-mono: "IBM Plex Mono", monospace;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background:
    radial-gradient(circle at top right, rgba(15, 106, 82, 0.14), transparent 32%),
    linear-gradient(180deg, #f8f4ec 0%, #f4f0e8 45%, #efe8dc 100%);
  color: var(--ink);
  font-family: var(--font-body);
  line-height: 1.65;
}

a {
  color: inherit;
}

.page-shell {
  width: min(1180px, calc(100vw - 2rem));
  margin: 0 auto;
  padding: 1rem 0 5rem;
}

.top-nav {
  position: sticky;
  top: 0.8rem;
  z-index: 10;
  display: flex;
  flex-wrap: wrap;
  gap: 0.7rem;
  margin: 0 auto 1rem;
  padding: 0.85rem 1rem;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: rgba(251, 248, 242, 0.88);
  backdrop-filter: blur(10px);
  box-shadow: 0 16px 40px rgba(28, 33, 31, 0.06);
}

.top-nav a {
  padding: 0.45rem 0.8rem;
  border-radius: 999px;
  color: var(--muted);
  font-family: var(--font-mono);
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-decoration: none;
  text-transform: uppercase;
  transition: background-color 180ms ease, color 180ms ease;
}

.top-nav a:hover,
.top-nav a:focus-visible {
  background: var(--accent-soft);
  color: var(--ink);
}

.top-nav a:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.hero {
  display: grid;
  grid-template-columns: minmax(0, 1.4fr) minmax(280px, 0.8fr);
  gap: var(--space-5);
  padding: clamp(2rem, 4vw, 4rem);
  margin-top: 1rem;
  border: 1px solid var(--line);
  border-radius: 36px;
  background: rgba(251, 248, 242, 0.82);
  backdrop-filter: blur(10px);
  box-shadow: var(--shadow);
}

.eyebrow {
  margin: 0 0 var(--space-3);
  color: var(--accent);
  font-family: var(--font-mono);
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.18em;
  text-transform: uppercase;
}

.hero h1,
.section-heading h2 {
  margin: 0;
  font-family: var(--font-display);
  font-weight: 400;
  letter-spacing: -0.03em;
  line-height: 0.95;
}

.hero h1 {
  max-width: 10ch;
  font-size: clamp(3.5rem, 9vw, 7rem);
}

.lede {
  max-width: 58ch;
  margin: var(--space-4) 0 0;
  font-size: 1.08rem;
  color: var(--muted);
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.9rem;
  margin-top: var(--space-5);
}

.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 3rem;
  padding: 0 1.25rem;
  border-radius: 999px;
  border: 1px solid transparent;
  font-weight: 700;
  text-decoration: none;
  transition: transform 220ms ease, border-color 220ms ease, background-color 220ms ease;
}

.button:hover,
.button:focus-visible {
  transform: translateY(-1px);
}

.button:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
}

.button-primary {
  background: var(--accent);
  color: #f5f4ee;
}

.button-secondary {
  border-color: var(--line);
  background: transparent;
}

.hero-panel,
.card,
.step-card,
.summary-card,
.check-card,
.code-card {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--paper);
}

.hero-panel {
  padding: var(--space-5);
  background:
    linear-gradient(180deg, rgba(15, 106, 82, 0.07), rgba(15, 106, 82, 0) 52%),
    var(--paper);
}

.panel-label,
.code-label {
  margin: 0 0 var(--space-3);
  font-family: var(--font-mono);
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.16em;
  text-transform: uppercase;
}

.panel-list {
  margin: 0;
  padding-left: 1.2rem;
}

.panel-list li + li {
  margin-top: 0.8rem;
}

.section {
  margin-top: var(--space-8);
}

.chapter-strip {
  display: grid;
  grid-template-columns: minmax(0, 0.9fr) minmax(0, 1.1fr);
  gap: var(--space-5);
  align-items: start;
}

.chapter-intro h2 {
  margin: 0 0 1rem;
  font-family: var(--font-display);
  font-size: clamp(2.3rem, 5vw, 4rem);
  font-weight: 400;
  letter-spacing: -0.03em;
  line-height: 0.98;
}

.chapter-intro p:last-child {
  max-width: 54ch;
  color: var(--muted);
}

.chapter-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: var(--space-4);
}

.chapter-card,
.arch-node,
.fabric-band,
.architecture-rail {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--paper);
}

.chapter-card {
  padding: 1.4rem;
}

.chapter-card span,
.arch-label,
.arch-node-label {
  display: block;
  margin-bottom: 0.8rem;
  color: var(--accent);
  font-family: var(--font-mono);
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.16em;
  text-transform: uppercase;
}

.chapter-card h3 {
  margin: 0 0 0.45rem;
  font-size: 1.05rem;
}

.chapter-card p {
  margin: 0;
  color: var(--muted);
}

.section-grid {
  display: grid;
  gap: var(--space-5);
}

.section-heading {
  display: grid;
  gap: var(--space-3);
}

.section-heading h2 {
  font-size: clamp(2.6rem, 6vw, 4.5rem);
  max-width: 11ch;
}

.section-heading p {
  margin: 0;
  max-width: 62ch;
  color: var(--muted);
}

.section-heading.narrow h2 {
  max-width: 12ch;
}

.content-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: var(--space-4);
}

.card,
.step-card,
.summary-card,
.check-card,
.code-card {
  padding: var(--space-5);
}

.card h3,
.step-card h3,
.summary-card h3,
.check-card h3 {
  margin-top: 0;
  margin-bottom: 0.7rem;
  font-size: 1.15rem;
}

.card p:last-child,
.summary-card p:last-child,
.check-card p:last-child {
  margin-bottom: 0;
}

.accent-card {
  background: linear-gradient(180deg, var(--accent-soft), var(--paper) 42%);
}

.architecture-frame {
  display: grid;
  gap: var(--space-4);
}

.architecture-rail {
  padding: 1.2rem 1.4rem;
  background: linear-gradient(90deg, rgba(15, 106, 82, 0.12), rgba(15, 106, 82, 0.03));
}

.arch-note {
  color: var(--muted);
}

.architecture-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: var(--space-4);
}

.arch-node {
  padding: 1.5rem;
}

.arch-rank-row {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1rem;
}

.arch-rank {
  padding: 1rem;
  border: 1px solid var(--line);
  border-radius: 18px;
  background: var(--paper-strong);
}

.arch-rank strong,
.arch-rank span,
.arch-rank em {
  display: block;
}

.arch-rank strong {
  margin-bottom: 0.35rem;
}

.arch-rank span {
  color: var(--muted);
}

.arch-rank em {
  margin-top: 0.8rem;
  font-style: normal;
  color: var(--accent);
  font-family: var(--font-mono);
  font-size: 0.88rem;
}

.fabric-band {
  padding: 1.3rem 1.5rem;
  background: var(--contrast);
  color: var(--contrast-2);
}

.fabric-band span {
  display: block;
  margin-bottom: 0.45rem;
  font-family: var(--font-mono);
  font-size: 0.82rem;
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
}

.fabric-band p {
  margin: 0;
}

.term-list {
  display: grid;
  grid-template-columns: minmax(0, 120px) minmax(0, 1fr);
  gap: 0.7rem 1rem;
  margin: 0;
}

.term-list dt {
  font-family: var(--font-mono);
  font-weight: 600;
}

.term-list dd {
  margin: 0;
}

.steps {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: var(--space-4);
}

.step-card {
  position: relative;
  min-height: 220px;
}

.step-index {
  display: inline-block;
  margin-bottom: 2.5rem;
  color: var(--accent);
  font-family: var(--font-mono);
  font-size: 0.82rem;
  font-weight: 600;
  letter-spacing: 0.18em;
}

pre {
  margin: 1rem 0 0;
  padding: 1rem 1.1rem;
  overflow-x: auto;
  border-radius: var(--radius-sm);
  background: #202825;
  color: #edf2ee;
  font-family: var(--font-mono);
  font-size: 0.92rem;
  line-height: 1.55;
}

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

:not(pre) > code {
  padding: 0.08rem 0.35rem;
  border-radius: 0.35rem;
  background: rgba(15, 106, 82, 0.08);
}

.small-note {
  font-size: 0.95rem;
}

.contrast-band {
  padding: clamp(1.5rem, 3vw, 2rem);
  border-radius: 32px;
  background: var(--contrast);
  color: var(--contrast-2);
}

.contrast-band .section-heading p,
.contrast-band h2,
.contrast-band h3,
.contrast-band p {
  color: inherit;
}

.contrast-band .eyebrow {
  color: #93d2be;
}

.code-layout {
  display: grid;
  grid-template-columns: 1.2fr 0.8fr;
  gap: var(--space-4);
  margin-top: var(--space-5);
}

.dark-card {
  background: rgba(255, 255, 255, 0.04);
  border-color: rgba(255, 255, 255, 0.08);
}

.table-like {
  display: grid;
  gap: 0;
  border: 1px solid var(--line);
  border-radius: 24px;
  overflow: hidden;
  background: var(--paper);
}

.table-row {
  display: grid;
  grid-template-columns: minmax(180px, 0.5fr) minmax(0, 1.5fr);
}

.table-row > div {
  padding: 1rem 1.2rem;
  border-top: 1px solid var(--line);
}

.table-row > div:first-child {
  border-right: 1px solid var(--line);
  font-family: var(--font-mono);
  font-size: 0.9rem;
}

.table-head {
  background: var(--paper-strong);
  font-weight: 700;
}

.table-head > div {
  border-top: 0;
}

.split-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.check-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: var(--space-4);
}

.closing-section {
  padding-bottom: 3rem;
}

.summary-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: var(--space-4);
}

.summary-card {
  background: var(--paper-strong);
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  .button {
    transition: none;
  }
}

@media (max-width: 1100px) {
  .chapter-strip,
  .hero,
  .content-grid,
  .steps,
  .check-grid,
  .summary-grid,
  .code-layout {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .architecture-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 820px) {
  .page-shell {
    width: min(100vw - 1rem, 100%);
  }

  .top-nav {
    top: 0.5rem;
    border-radius: 24px;
  }

  .hero,
  .chapter-strip,
  .chapter-grid,
  .content-grid,
  .steps,
  .check-grid,
  .summary-grid,
  .code-layout,
  .split-grid,
  .architecture-grid,
  .arch-rank-row,
  .table-row {
    grid-template-columns: 1fr;
  }

  .hero h1 {
    max-width: 100%;
    font-size: clamp(2.8rem, 16vw, 5rem);
  }

  .section-heading h2 {
    max-width: 100%;
    font-size: clamp(2.2rem, 12vw, 3.6rem);
  }

  .table-row > div:first-child {
    border-right: 0;
    border-bottom: 1px solid var(--line);
  }

  .card,
  .step-card,
  .summary-card,
  .check-card,
  .code-card,
  .hero-panel {
    padding: 1.25rem;
  }
}