:root {
  --ink: #17324d;
  --ink-soft: #38556d;
  --muted: #5f6f83;
  --paper: #f6f5ef;
  --surface: #fffef9;
  --surface-alt: #edf4f2;
  --teal: #0f766e;
  --teal-dark: #0b5f59;
  --teal-pale: #d9eeea;
  --blue-pale: #e8f0f6;
  --amber: #8b5a10;
  --amber-pale: #fbf1dc;
  --red: #a62c24;
  --red-pale: #fbe9e6;
  --border: #d8dfe2;
  --border-strong: #b9c6cd;
  --shadow: 0 18px 50px rgba(23, 50, 77, 0.07);
  --sans: Inter, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --serif: "Iowan Old Style", "Palatino Linotype", Palatino, Georgia, serif;
  --mono: "Cascadia Code", "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  --sidebar-width: 292px;
  --topbar-height: 64px;
  --content-width: 1120px;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--topbar-height) + 28px);
}

body {
  margin: 0;
  color: var(--ink);
  background: var(--paper);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.68;
  text-rendering: optimizeLegibility;
}

::selection {
  background: var(--teal-pale);
  color: var(--ink);
}

a {
  color: var(--teal);
  text-decoration-thickness: 1px;
  text-underline-offset: 0.2em;
}

a:hover {
  color: var(--teal-dark);
}

a:focus-visible,
button:focus-visible,
summary:focus-visible {
  outline: 3px solid var(--amber);
  outline-offset: 3px;
}

button,
input,
select,
textarea {
  font: inherit;
}

svg {
  display: block;
}

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

.skip-link {
  position: fixed;
  top: 10px;
  left: 12px;
  z-index: 1000;
  padding: 10px 14px;
  color: white;
  background: var(--ink);
  border-radius: 8px;
  transform: translateY(-150%);
  transition: transform 160ms ease;
}

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

.reading-progress {
  position: fixed;
  inset: 0 0 auto;
  z-index: 110;
  height: 3px;
  background: transparent;
  pointer-events: none;
}

.reading-progress span {
  display: block;
  width: 0;
  height: 100%;
  background: var(--teal);
  transition: width 90ms linear;
}

.topbar {
  position: fixed;
  inset: 0 0 auto;
  z-index: 100;
  height: var(--topbar-height);
  display: grid;
  grid-template-columns: auto 1fr auto;
  align-items: center;
  gap: 18px;
  padding: 0 28px;
  color: var(--ink);
  background: rgba(255, 254, 249, 0.94);
  border-bottom: 1px solid var(--border);
  backdrop-filter: blur(14px);
}

.topbar-title {
  color: var(--ink);
  font-family: var(--serif);
  font-size: 1.05rem;
  font-weight: 700;
  text-decoration: none;
}

.topbar-meta {
  display: flex;
  align-items: center;
  gap: 18px;
  color: var(--muted);
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.07em;
  text-transform: uppercase;
}

.topbar-meta a {
  display: inline-flex;
  min-height: 42px;
  align-items: center;
  color: var(--ink);
  text-decoration: none;
}

.menu-button {
  display: none;
  width: 44px;
  height: 44px;
  padding: 0;
  place-items: center;
  color: var(--ink);
  background: transparent;
  border: 1px solid var(--border);
  border-radius: 50%;
  cursor: pointer;
}

.site-shell {
  display: grid;
  grid-template-columns: var(--sidebar-width) minmax(0, 1fr);
  min-height: 100vh;
  padding-top: var(--topbar-height);
}

.sidebar {
  position: sticky;
  top: var(--topbar-height);
  height: calc(100vh - var(--topbar-height));
  display: flex;
  flex-direction: column;
  overflow-y: auto;
  padding: 28px 24px 22px;
  background: #f0efe8;
  border-right: 1px solid var(--border);
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  padding-bottom: 24px;
  border-bottom: 1px solid var(--border);
}

.brand-mark {
  flex: 0 0 auto;
  color: var(--teal);
}

.brand-mark:hover {
  color: var(--teal-dark);
}

.brand-kicker,
.brand-title,
.nav-label,
.eyebrow,
.mini-label,
.definition-label,
.code-label,
.case-badge span {
  margin: 0;
  font-size: 0.68rem;
  font-weight: 800;
  letter-spacing: 0.13em;
  line-height: 1.4;
  text-transform: uppercase;
}

.brand-kicker {
  color: #5c6b7d;
}

.brand-title {
  margin-top: 3px;
  color: var(--ink);
  font-size: 0.82rem;
  letter-spacing: 0.04em;
  text-transform: none;
}

.course-links {
  display: flex;
  flex-direction: column;
  gap: 3px;
  padding: 24px 0;
}

.nav-label {
  padding: 0 10px 8px;
  color: #5c6b7d;
}

.nav-label-spaced {
  padding-top: 22px;
}

.nav-link {
  display: grid;
  grid-template-columns: 30px 1fr;
  gap: 3px;
  align-items: center;
  min-height: 42px;
  padding: 7px 10px;
  color: var(--ink-soft);
  border-radius: 6px;
  font-size: 0.84rem;
  line-height: 1.35;
  text-decoration: none;
  transition: background-color 160ms ease, color 160ms ease;
}

.nav-link span {
  color: #5c6b7d;
  font-family: var(--mono);
  font-size: 0.7rem;
}

.nav-link:hover {
  color: var(--ink);
  background: rgba(255, 254, 249, 0.72);
}

.nav-link.is-active {
  color: var(--ink);
  background: var(--surface);
  box-shadow: inset 3px 0 var(--teal);
}

.nav-link.is-active span {
  color: var(--teal);
}

.sidebar-note {
  display: grid;
  grid-template-columns: 10px 1fr;
  gap: 10px;
  margin-top: auto;
  padding: 16px 14px;
  color: var(--muted);
  background: rgba(255, 254, 249, 0.62);
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 0.76rem;
  line-height: 1.5;
}

.sidebar-note p {
  margin: 0;
}

.status-dot {
  width: 8px;
  height: 8px;
  margin-top: 6px;
  background: var(--teal);
  border-radius: 50%;
  box-shadow: 0 0 0 4px var(--teal-pale);
}

main {
  min-width: 0;
}

.chapter {
  width: min(100%, var(--content-width));
  margin: 0 auto;
  padding: 88px 56px;
  border-bottom: 1px solid var(--border);
}

.hero {
  display: grid;
  grid-template-columns: minmax(0, 1.03fr) minmax(420px, 0.97fr);
  gap: 54px;
  align-items: center;
  min-height: calc(100vh - var(--topbar-height));
  padding-top: 64px;
  padding-bottom: 64px;
}

.eyebrow {
  display: flex;
  flex-wrap: wrap;
  gap: 9px;
  align-items: center;
  color: var(--teal);
}

.eyebrow span {
  display: inline-flex;
  align-items: center;
  min-height: 23px;
  padding: 1px 7px;
  color: var(--teal-dark);
  background: var(--teal-pale);
  border-radius: 3px;
  letter-spacing: 0.08em;
}

.hero h1 {
  max-width: 720px;
  margin: 26px 0 24px;
  font-family: var(--serif);
  font-size: clamp(2.85rem, 5.2vw, 5.1rem);
  font-weight: 500;
  letter-spacing: -0.055em;
  line-height: 1.02;
}

.hero-lede {
  max-width: 660px;
  margin: 0;
  color: var(--ink-soft);
  font-size: clamp(1rem, 1.4vw, 1.12rem);
  line-height: 1.8;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 30px;
}

.button {
  display: inline-flex;
  min-height: 46px;
  align-items: center;
  justify-content: center;
  padding: 10px 18px;
  border: 1px solid transparent;
  border-radius: 4px;
  font-size: 0.82rem;
  font-weight: 750;
  letter-spacing: 0.03em;
  text-decoration: none;
  transition: background-color 180ms ease, color 180ms ease, border-color 180ms ease;
}

.button-primary {
  color: white;
  background: var(--ink);
}

.button-primary:hover {
  color: white;
  background: var(--teal-dark);
}

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

.button-secondary:hover {
  color: var(--ink);
  background: var(--surface);
  border-color: var(--ink-soft);
}

.course-facts {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 1px;
  margin-top: 46px;
  background: var(--border);
  border: 1px solid var(--border);
}

.course-facts div {
  min-width: 0;
  padding: 17px 15px;
  background: var(--surface);
}

.course-facts strong,
.course-facts span {
  display: block;
}

.course-facts strong {
  color: var(--ink);
  font-family: var(--serif);
  font-size: 1.25rem;
  line-height: 1.2;
}

.course-facts span {
  margin-top: 5px;
  color: var(--muted);
  font-size: 0.7rem;
  line-height: 1.35;
}

.workflow-panel {
  position: relative;
  padding: 24px;
  background: var(--surface);
  border: 1px solid var(--border);
  box-shadow: var(--shadow);
}

.workflow-heading {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 14px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--border);
}

.workflow-heading span {
  color: var(--teal);
  font-size: 0.68rem;
  font-weight: 800;
  letter-spacing: 0.13em;
}

.workflow-heading p {
  margin: 0;
  color: var(--muted);
  font-size: 0.7rem;
}

.cycle-svg {
  width: 100%;
  max-width: 610px;
  height: auto;
  margin: 6px auto -8px;
  overflow: visible;
}

.cycle-ring {
  fill: none;
  stroke: var(--border-strong);
  stroke-width: 1.3;
  stroke-dasharray: 3 8;
}

.cycle-ring-inner {
  fill: var(--surface-alt);
  stroke: var(--border);
  stroke-width: 1;
}

.cycle-arrow path {
  fill: none;
  stroke: var(--teal);
  stroke-linecap: round;
  stroke-width: 1.3;
  stroke-dasharray: 4 12;
  opacity: 0.55;
}

.cycle-node circle {
  fill: var(--surface);
  stroke: var(--border-strong);
  stroke-width: 1.15;
  transition: fill 180ms ease, stroke 180ms ease;
}

.cycle-node text {
  fill: var(--ink);
  font-family: var(--sans);
  font-size: 14px;
  font-weight: 700;
  pointer-events: none;
}

.cycle-node:hover circle {
  fill: var(--teal-pale);
  stroke: var(--teal);
}

.cycle-node:focus {
  outline: none;
}

.cycle-node:focus-visible circle {
  stroke: var(--amber);
  stroke-width: 4;
}

.cycle-centre {
  fill: var(--ink);
}

.cycle-centre-title {
  fill: white;
  font-family: var(--serif);
  font-size: 26px;
  font-weight: 700;
  letter-spacing: 0.02em;
}

.cycle-centre-copy {
  fill: #bdcbd7;
  font-family: var(--sans);
  font-size: 11px;
  letter-spacing: 0.06em;
}

.phase-list {
  display: none;
  padding: 0;
  margin: 20px 0 0;
  list-style: none;
}

.phase-list a {
  display: grid;
  grid-template-columns: 34px 1fr;
  align-items: center;
  min-height: 46px;
  padding: 8px 0;
  color: var(--ink);
  border-top: 1px solid var(--border);
  text-decoration: none;
}

.phase-list span {
  color: var(--teal);
  font-family: var(--mono);
  font-size: 0.72rem;
}

.orientation {
  padding-top: 74px;
  padding-bottom: 74px;
  background: var(--surface);
}

.section-intro {
  max-width: 890px;
}

.section-intro h2,
.chapter-heading h2,
.case-header h2 {
  margin: 18px 0 16px;
  font-family: var(--serif);
  font-size: clamp(2rem, 3.3vw, 3.35rem);
  font-weight: 500;
  letter-spacing: -0.035em;
  line-height: 1.12;
}

.section-intro p,
.chapter-lede {
  max-width: 810px;
  margin: 0;
  color: var(--ink-soft);
  font-size: 1.02rem;
}

.outcome-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 16px;
  margin-top: 38px;
}

.course-plan {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 1px;
  margin-top: 18px;
  background: var(--border);
  border: 1px solid var(--border);
}

.course-plan article {
  padding: 18px;
  background: var(--surface);
}

.course-plan span,
.course-plan strong {
  display: block;
}

.course-plan span {
  color: var(--teal);
  font-size: 0.66rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.course-plan strong {
  margin: 5px 0 4px;
  font-family: var(--serif);
  font-size: 1.12rem;
}

.course-plan p {
  margin: 0;
  color: var(--muted);
  font-size: 0.78rem;
}

.outcome-card {
  min-height: 210px;
  padding: 24px;
  background: var(--paper);
  border: 1px solid var(--border);
}

.card-number {
  display: inline-block;
  padding-bottom: 22px;
  color: var(--teal);
  font-family: var(--mono);
  font-size: 0.76rem;
}

.outcome-card h3,
.audit-grid h3,
.model-grid h3,
.metric-grid h3,
.deployment-grid h3,
.checklist-grid h3 {
  margin: 0 0 10px;
  font-family: var(--serif);
  font-size: 1.28rem;
  line-height: 1.25;
}

.outcome-card p,
.audit-grid p,
.model-grid p,
.metric-grid p,
.deployment-grid p {
  margin: 0;
  color: var(--muted);
  font-size: 0.86rem;
}

.lesson {
  background: var(--paper);
}

.chapter-heading {
  max-width: 900px;
}

.learning-box {
  display: grid;
  grid-template-columns: minmax(140px, 0.26fr) minmax(0, 0.74fr);
  gap: 28px;
  margin: 34px 0;
  padding: 22px 24px;
  background: var(--surface);
  border-top: 2px solid var(--teal);
  border-bottom: 1px solid var(--border);
}

.mini-label {
  color: var(--teal);
}

.learning-box ul {
  margin: 0;
  padding-left: 20px;
}

.learning-box li + li {
  margin-top: 7px;
}

h3 {
  color: var(--ink);
}

.two-column {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 26px;
  align-items: start;
  margin: 30px 0;
}

.two-column h3 {
  margin-top: 0;
  font-family: var(--serif);
  font-size: 1.38rem;
}

.two-column p {
  color: var(--ink-soft);
}

.two-column-wide {
  grid-template-columns: 1.25fr 0.75fr;
}

.definition-card {
  padding: 24px;
  background: var(--ink);
  color: white;
}

.definition-card p {
  margin: 12px 0 0;
  color: #e2eaf0;
  font-family: var(--serif);
  font-size: 1.06rem;
  line-height: 1.7;
}

.definition-card strong {
  color: #fff4c7;
}

.definition-label {
  color: #8fd4cc;
}

.table-wrap {
  width: 100%;
  margin: 32px 0;
  overflow-x: auto;
  border: 1px solid var(--border);
  background: var(--surface);
}

table {
  width: 100%;
  min-width: 720px;
  border-collapse: collapse;
  font-size: 0.86rem;
}

caption {
  padding: 15px 18px;
  color: var(--ink);
  background: var(--surface-alt);
  border-bottom: 1px solid var(--border);
  font-size: 0.78rem;
  font-weight: 750;
  text-align: left;
}

th,
td {
  padding: 14px 17px;
  border-bottom: 1px solid var(--border);
  text-align: left;
  vertical-align: top;
}

thead th {
  color: var(--muted);
  background: #f8f8f4;
  font-size: 0.68rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

tbody th {
  color: var(--ink);
  font-weight: 750;
}

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

.code-block {
  position: relative;
  margin: 28px 0;
  overflow: hidden;
  background: #10283a;
  border: 1px solid #29485e;
}

.code-label {
  padding: 12px 18px;
  color: #9fc2d5;
  background: #0c2131;
  border-bottom: 1px solid #29485e;
}

pre {
  max-width: 100%;
  margin: 0;
  padding: 22px;
  overflow-x: auto;
  color: #e6edf2;
  font-size: 0.82rem;
  line-height: 1.7;
}

code {
  color: inherit;
}

:not(pre) > code {
  padding: 0.1em 0.35em;
  color: var(--teal-dark);
  background: var(--teal-pale);
  border-radius: 3px;
  font-size: 0.86em;
}

.copy-button {
  position: absolute;
  top: 42px;
  right: 12px;
  min-width: 62px;
  min-height: 34px;
  padding: 5px 9px;
  color: #c1d6e2;
  background: #17384c;
  border: 1px solid #365a70;
  border-radius: 3px;
  font-size: 0.66rem;
  font-weight: 750;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  cursor: pointer;
}

.copy-button:hover {
  color: white;
  border-color: #8eb4c7;
}

.callout {
  display: grid;
  grid-template-columns: 26px 1fr;
  gap: 14px;
  margin: 30px 0;
  padding: 20px 22px;
  border: 1px solid var(--border);
}

.callout svg {
  margin-top: 2px;
}

.callout strong {
  display: block;
  margin-bottom: 5px;
}

.callout p,
.callout ol {
  margin: 0;
  color: var(--ink-soft);
  font-size: 0.88rem;
}

.callout-note {
  background: var(--surface);
  border-left: 4px solid var(--ink-soft);
}

.callout-no-icon {
  grid-template-columns: 1fr;
  padding: 22px 24px;
}

.callout-no-icon ol {
  display: grid;
  gap: 3px;
  padding-left: 0;
  margin-top: 12px;
  list-style: none;
  counter-reset: callout-step;
}

.callout-no-icon li {
  position: relative;
  min-height: 34px;
  padding: 6px 0 6px 38px;
  border-top: 1px solid var(--border);
  counter-increment: callout-step;
}

.callout-no-icon li::before {
  position: absolute;
  top: 6px;
  left: 0;
  display: grid;
  width: 26px;
  height: 26px;
  place-items: center;
  color: var(--teal-dark);
  background: var(--teal-pale);
  border-radius: 50%;
  content: counter(callout-step);
  font-family: var(--mono);
  font-size: 0.65rem;
  font-weight: 800;
}

.callout-warning {
  color: var(--amber);
  background: var(--amber-pale);
  border-color: #e9d4a7;
  border-left: 4px solid var(--amber);
}

.callout-warning p,
.callout-warning strong {
  color: #624819;
}

.callout-success {
  grid-template-columns: 1fr;
  color: var(--teal);
  background: var(--surface-alt);
  border-color: #c7dfda;
  border-left: 4px solid var(--teal);
}

.callout-success p,
.callout-success strong {
  color: #174c47;
}

.checkpoint {
  margin: 26px 0;
  background: var(--surface);
  border: 1px solid var(--border);
}

.checkpoint summary {
  min-height: 52px;
  padding: 14px 18px;
  color: var(--ink);
  font-size: 0.86rem;
  font-weight: 750;
  cursor: pointer;
}

.checkpoint p {
  margin: 0;
  padding: 0 18px 18px;
  color: var(--ink-soft);
  font-size: 0.88rem;
}

.exercise {
  margin: 26px 0;
  padding: 20px 22px;
  background: var(--surface-alt);
  border: 1px solid #c7dfda;
  border-left: 4px solid var(--teal);
}

.exercise > p {
  margin: 8px 0 0;
  color: var(--ink-soft);
  font-size: 0.9rem;
}

.exercise details {
  margin-top: 12px;
  border-top: 1px solid #c7dfda;
}

.exercise summary {
  padding-top: 11px;
  color: var(--teal-dark);
  font-size: 0.78rem;
  font-weight: 800;
  cursor: pointer;
}

.exercise details p {
  margin: 0;
  padding: 9px 0 0;
  color: var(--ink-soft);
  font-size: 0.86rem;
}

.deliverable {
  display: grid;
  grid-template-columns: 130px 1fr;
  gap: 18px;
  align-items: start;
  margin-top: 28px;
  padding: 18px 20px;
  background: var(--ink);
  color: white;
}

.deliverable span {
  color: #8ed3ca;
  font-family: var(--mono);
  font-size: 0.7rem;
}

.deliverable p {
  margin: 0;
  color: #dce7ef;
  font-size: 0.86rem;
}

.deliverable code {
  color: #fff1b6;
}

.deliverable-body > strong {
  display: block;
  color: white;
  font-family: var(--serif);
  font-size: 1.15rem;
}

.deliverable-body > p {
  margin: 5px 0 0;
}

.done-when {
  padding-top: 10px;
  border-top: 1px solid rgba(255, 255, 255, 0.22);
}

.done-when b {
  color: #fff1b6;
}

.artifact-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 14px;
}

.artifact-actions a {
  display: inline-flex;
  min-height: 36px;
  align-items: center;
  padding: 6px 11px;
  color: var(--ink);
  background: white;
  border: 1px solid transparent;
  border-radius: 3px;
  font-size: 0.72rem;
  font-weight: 800;
  text-decoration: none;
}

.artifact-actions a:hover {
  background: var(--teal-pale);
}

.artifact-check {
  display: inline-flex;
  min-height: 38px;
  align-items: center;
  gap: 8px;
  margin-top: 11px;
  color: #dce7ef;
  font-size: 0.75rem;
  font-weight: 700;
  cursor: pointer;
}

.artifact-check input {
  width: 17px;
  height: 17px;
  accent-color: var(--teal);
}

.artifact-progress {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 10px 20px;
  margin: 18px 0 0;
  padding: 13px 16px;
  color: var(--muted);
  background: var(--surface);
  border: 1px solid var(--border);
  font-size: 0.78rem;
}

.artifact-progress strong {
  color: var(--ink);
}

.audit-grid,
.model-grid,
.metric-grid,
.deployment-grid {
  display: grid;
  gap: 14px;
  margin: 32px 0;
}

.audit-grid {
  grid-template-columns: repeat(4, minmax(0, 1fr));
}

.model-grid,
.metric-grid,
.deployment-grid {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.audit-grid article,
.model-grid article,
.metric-grid article,
.deployment-grid article {
  padding: 20px;
  background: var(--surface);
  border-top: 2px solid var(--border-strong);
}

.audit-grid article:nth-child(odd),
.model-grid article:nth-child(2),
.metric-grid article:nth-child(2),
.deployment-grid article:nth-child(2) {
  border-top-color: var(--teal);
}

.metric-strip {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 1px;
  margin: 30px 0;
  background: var(--border);
  border: 1px solid var(--border);
}

.metric-strip div {
  padding: 18px;
  background: var(--surface);
}

.metric-strip span,
.metric-strip strong {
  display: block;
}

.metric-strip span {
  color: var(--muted);
  font-size: 0.68rem;
  font-weight: 750;
  letter-spacing: 0.07em;
  text-transform: uppercase;
}

.metric-strip strong {
  margin-top: 5px;
  color: var(--ink);
  font-family: var(--serif);
  font-size: 1.3rem;
}

.metric-strip-accent div {
  background: var(--surface-alt);
}

.split-diagram {
  display: grid;
  grid-template-columns: 60fr 20fr 20fr;
  gap: 3px;
  min-height: 98px;
  margin: 30px 0;
  background: var(--surface);
  border: 1px solid var(--border);
}

.split-zone {
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding: 18px;
}

.split-zone span,
.split-zone strong {
  display: block;
}

.split-zone span {
  color: var(--muted);
  font-size: 0.68rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.split-zone strong {
  margin-top: 4px;
  font-family: var(--serif);
  font-size: 1.02rem;
}

.split-train {
  color: white;
  background: var(--ink);
}

.split-train span {
  color: #b9cbd7;
}

.split-validation {
  background: var(--teal-pale);
}

.split-test {
  background: var(--amber-pale);
}

.check-list {
  margin: 14px 0 0;
  padding: 0;
  list-style: none;
}

.check-list li {
  position: relative;
  padding: 8px 0 8px 24px;
  border-bottom: 1px solid var(--border);
}

.check-list li::before {
  position: absolute;
  top: 9px;
  left: 0;
  color: var(--teal);
  content: "✓";
  font-weight: 900;
}

.small-note {
  padding: 22px;
  background: var(--surface-alt);
  border-left: 3px solid var(--teal);
}

.small-note p:last-child {
  margin: 9px 0 0;
  color: var(--ink-soft);
  font-size: 0.88rem;
}

.tag {
  display: inline-block;
  margin-bottom: 14px;
  color: var(--teal);
  font-size: 0.66rem;
  font-weight: 800;
  letter-spacing: 0.09em;
  text-transform: uppercase;
}

.reading-note {
  margin: 18px 0;
  color: var(--ink-soft);
  font-size: 0.9rem;
}

.metric-symbol {
  display: inline-flex;
  min-height: 34px;
  align-items: center;
  margin-bottom: 12px;
  padding: 4px 9px;
  color: white;
  background: var(--ink);
  font-family: var(--mono);
  font-size: 0.72rem;
}

.decision-table {
  margin: 28px 0;
  border: 1px solid var(--border);
}

.decision-row {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 20px;
  align-items: center;
  min-height: 56px;
  padding: 12px 18px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
}

.decision-row:last-child {
  border-bottom: 0;
}

.decision-row span {
  color: var(--ink-soft);
  font-size: 0.85rem;
}

.decision-row strong {
  color: var(--teal-dark);
  font-size: 0.8rem;
}

.delivery-stack {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  align-items: center;
  margin: 30px 0;
}

.delivery-stack div {
  flex: 1 1 180px;
  padding: 16px;
  background: var(--surface);
  border: 1px solid var(--border);
}

.delivery-stack span,
.delivery-stack strong {
  display: block;
}

.delivery-stack span {
  color: var(--muted);
  font-size: 0.66rem;
  text-transform: uppercase;
}

.delivery-stack strong {
  margin-top: 4px;
  font-family: var(--serif);
}

.delivery-stack > svg {
  flex: 0 0 auto;
  color: var(--teal);
}

.case-labs {
  background: var(--surface);
}

.case-lab-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 18px;
  margin-top: 34px;
}

.case-lab-card {
  display: flex;
  min-width: 0;
  flex-direction: column;
  overflow: hidden;
  color: var(--ink);
  background: var(--paper);
  border: 1px solid var(--border);
  text-decoration: none;
  transition: border-color 180ms ease, transform 180ms ease, box-shadow 180ms ease;
}

.case-lab-card:hover {
  color: var(--ink);
  border-color: var(--teal);
  box-shadow: 0 16px 34px rgba(23, 50, 77, 0.09);
  transform: translateY(-3px);
}

.case-lab-card:focus-visible {
  border-color: var(--amber);
}

.case-visual {
  position: relative;
  aspect-ratio: 4 / 2.7;
  overflow: hidden;
  background: #eef2f1;
  border-bottom: 1px solid var(--border);
}

.case-visual img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 240ms ease;
}

.case-lab-card:hover .case-visual img {
  transform: scale(1.018);
}

.case-label {
  position: absolute;
  top: 12px;
  left: 12px;
  padding: 5px 8px;
  color: white;
  background: rgba(23, 50, 77, 0.9);
  font-family: var(--mono);
  font-size: 0.61rem;
  font-weight: 700;
  letter-spacing: 0.06em;
}

.case-card-body {
  display: flex;
  flex: 1;
  flex-direction: column;
  padding: 22px;
}

.case-card-body h3 {
  margin: 0 0 10px;
  font-family: var(--serif);
  font-size: 1.45rem;
  font-weight: 500;
}

.case-card-body p {
  margin: 0;
  color: var(--ink-soft);
  font-size: 0.86rem;
}

.case-metrics {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1px;
  margin: 20px 0;
  background: var(--border);
  border: 1px solid var(--border);
}

.case-metrics span {
  padding: 10px;
  color: var(--muted);
  background: var(--surface);
  font-size: 0.68rem;
  line-height: 1.35;
}

.case-metrics b {
  display: block;
  color: var(--teal-dark);
  font-family: var(--serif);
  font-size: 1.08rem;
}

.case-link {
  display: inline-flex;
  min-height: 44px;
  align-items: center;
  gap: 8px;
  margin-top: auto;
  color: var(--teal-dark);
  font-size: 0.8rem;
  font-weight: 800;
}

.case-link span {
  transition: transform 180ms ease;
}

.case-lab-card:hover .case-link span {
  transform: translateX(4px);
}

.compact-figure {
  max-width: 1000px;
}

.diagram-figure {
  max-width: none;
}

.diagram-figure img {
  width: 100%;
}

.case-study {
  background: var(--surface);
}

.case-header {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 30px;
  align-items: start;
}

.case-header > div:first-child {
  max-width: 760px;
}

.case-header p:last-child {
  color: var(--ink-soft);
}

.case-badge {
  min-width: 180px;
  padding: 16px;
  background: var(--ink);
  color: white;
}

.case-badge span {
  color: #8fd0c8;
}

.case-badge strong {
  display: block;
  margin-top: 5px;
  font-family: var(--serif);
  font-size: 1.02rem;
}

.case-flow {
  display: flex;
  flex-wrap: wrap;
  gap: 9px;
  align-items: center;
  margin: 34px 0;
  padding: 14px 18px;
  background: var(--surface-alt);
  border: 1px solid #d0e3df;
  color: var(--teal-dark);
  font-size: 0.72rem;
  font-weight: 750;
}

.case-flow i {
  width: 26px;
  height: 1px;
  background: var(--teal);
}

.figure-panel {
  margin: 34px 0;
  padding: 16px;
  background: var(--paper);
  border: 1px solid var(--border);
}

.figure-panel img {
  display: block;
  width: 100%;
  height: auto;
  background: var(--surface);
}

.figure-panel figcaption {
  padding: 13px 2px 0;
  color: var(--muted);
  font-size: 0.75rem;
  line-height: 1.55;
}

.comparison-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin: 28px 0;
}

.comparison-card {
  padding: 22px;
  background: var(--paper);
  border: 1px solid var(--border);
}

.comparison-card h3 {
  margin: 6px 0 16px;
  font-family: var(--serif);
  font-size: 1.45rem;
}

.comparison-card h3 span {
  color: var(--teal-dark);
}

.comparison-card dl {
  margin: 0;
  border-top: 1px solid var(--border);
}

.comparison-card dl div {
  display: flex;
  justify-content: space-between;
  gap: 20px;
  padding: 8px 0;
  border-bottom: 1px solid var(--border);
}

.comparison-card dt {
  color: var(--muted);
  font-size: 0.76rem;
}

.comparison-card dd {
  margin: 0;
  font-family: var(--mono);
  font-size: 0.78rem;
}

.case-insight {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(220px, 0.35fr);
  gap: 28px;
  align-items: start;
  padding: 24px;
  background: var(--paper);
  border-left: 4px solid var(--teal);
}

.case-insight:not(:has(.case-code-link)) {
  grid-template-columns: 1fr;
}

.case-insight h3 {
  margin: 0 0 8px;
  font-family: var(--serif);
  font-size: 1.3rem;
}

.case-insight p {
  margin: 0;
  color: var(--ink-soft);
}

.case-code-link a {
  display: inline-flex;
  min-height: 44px;
  align-items: center;
  gap: 5px;
  margin-top: 8px;
  font-size: 0.84rem;
  font-weight: 750;
}

.case-code-link {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
}

.checklist-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin: 34px 0;
  background: var(--border);
  border: 1px solid var(--border);
}

.checklist-grid article {
  padding: 22px;
  background: var(--surface);
}

.checklist-grid article:last-child {
  grid-column: 1 / -1;
}

.closing-card {
  padding: clamp(28px, 5vw, 54px);
  color: white;
  background: var(--ink);
}

.closing-card .eyebrow {
  color: #9fdad2;
}

.closing-card h3 {
  max-width: 760px;
  margin: 18px 0 16px;
  color: white;
  font-family: var(--serif);
  font-size: clamp(1.8rem, 3.2vw, 3rem);
  font-weight: 500;
  letter-spacing: -0.03em;
  line-height: 1.15;
}

.closing-card > p:not(.eyebrow) {
  max-width: 720px;
  margin: 0;
  color: #c7d4de;
}

.closing-card .button-primary {
  color: var(--ink);
  background: white;
}

.closing-card .button-secondary {
  color: white;
  border-color: #668196;
}

.closing-card .button-secondary:hover {
  color: var(--ink);
  background: white;
}

.site-footer {
  display: flex;
  justify-content: space-between;
  gap: 30px;
  width: min(100%, var(--content-width));
  margin: 0 auto;
  padding: 34px 56px 56px;
}

.site-footer strong {
  font-family: var(--serif);
  font-size: 1.05rem;
}

.site-footer p {
  margin: 3px 0 0;
  color: var(--muted);
  font-size: 0.76rem;
}

.footer-links {
  display: flex;
  flex-wrap: wrap;
  gap: 18px;
  align-items: center;
  font-size: 0.78rem;
}

.mobile-scrim {
  position: fixed;
  inset: var(--topbar-height) 0 0;
  z-index: 70;
  background: rgba(15, 31, 44, 0.38);
}

.reveal {
  opacity: 0;
  transform: translateY(10px);
  transition: opacity 320ms ease, transform 320ms ease;
}

.reveal.is-visible {
  opacity: 1;
  transform: translateY(0);
}

@media (max-width: 1280px) {
  .chapter {
    padding-right: 42px;
    padding-left: 42px;
  }

  .hero {
    grid-template-columns: minmax(0, 1fr) minmax(380px, 0.85fr);
    gap: 34px;
  }

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

@media (max-width: 1080px) {
  .hero {
    grid-template-columns: 1fr;
  }

  .workflow-panel {
    max-width: 660px;
  }

  .cycle-svg {
    max-width: 560px;
  }

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

@media (max-width: 920px) {
  :root {
    --topbar-height: 60px;
  }

  body.nav-open {
    overflow: hidden;
  }

  .topbar {
    grid-template-columns: auto 1fr auto;
    padding: 0 18px;
  }

  .menu-button {
    display: grid;
  }

  .topbar-title {
    font-size: 0.96rem;
  }

  .topbar-meta span {
    display: none;
  }

  .site-shell {
    display: block;
  }

  .sidebar {
    position: fixed;
    z-index: 80;
    top: var(--topbar-height);
    bottom: 0;
    left: 0;
    width: min(88vw, 330px);
    height: auto;
    transform: translateX(-105%);
    transition: transform 220ms ease;
  }

  .nav-open .sidebar {
    transform: translateX(0);
    box-shadow: 20px 0 55px rgba(23, 50, 77, 0.18);
  }

  .chapter {
    padding-right: 32px;
    padding-left: 32px;
  }

  .hero {
    min-height: auto;
  }
}

@media (max-width: 720px) {
  body {
    font-size: 15px;
  }

  .chapter {
    padding: 62px 22px;
  }

  .hero {
    padding-top: 44px;
  }

  .hero h1 {
    font-size: clamp(2.6rem, 12vw, 4.2rem);
  }

  .course-facts {
    grid-template-columns: 1fr;
  }

  .workflow-panel {
    padding: 18px;
  }

  .cycle-svg {
    display: none;
  }

  .phase-list {
    display: block;
  }

  .outcome-grid,
  .course-plan,
  .model-grid,
  .metric-grid,
  .deployment-grid,
  .case-lab-grid,
  .comparison-grid,
  .checklist-grid,
  .two-column,
  .two-column-wide,
  .case-insight {
    grid-template-columns: 1fr;
  }

  .learning-box {
    grid-template-columns: 1fr;
    gap: 12px;
  }

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

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

  .split-diagram {
    grid-template-columns: 1fr;
  }

  .case-header {
    grid-template-columns: 1fr;
  }

  .case-badge {
    min-width: 0;
  }

  .decision-row {
    grid-template-columns: 1fr;
    gap: 6px;
  }

  .deliverable {
    grid-template-columns: 1fr;
    gap: 5px;
  }

  .site-footer {
    flex-direction: column;
    padding: 30px 22px 46px;
  }

  .checklist-grid article:last-child {
    grid-column: auto;
  }

  .delivery-stack {
    align-items: stretch;
    flex-direction: column;
  }

  .delivery-stack > svg {
    align-self: center;
    transform: rotate(90deg);
  }
}

@media (max-width: 900px) {
  .diagram-figure {
    overflow-x: auto;
    overscroll-behavior-inline: contain;
    scrollbar-color: var(--teal) var(--blue-pale);
    scrollbar-width: thin;
  }

  .diagram-figure img {
    width: 760px;
    max-width: none;
  }

  .diagram-figure figcaption::after {
    content: " Scroll horizontally to inspect the full diagram.";
    color: var(--teal-dark);
    font-weight: 700;
  }
}

@media (max-width: 430px) {
  .topbar-meta {
    font-size: 0;
  }

  .topbar-meta a {
    font-size: 0.7rem;
  }

  .hero-actions .button {
    width: 100%;
  }

  .case-lab-grid {
    gap: 14px;
  }

  .metric-strip {
    grid-template-columns: 1fr;
  }

  .case-flow i {
    width: 16px;
  }

  .figure-panel {
    margin-right: -8px;
    margin-left: -8px;
    padding: 8px;
  }

}

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

  *,
  *::before,
  *::after {
    scroll-behavior: auto !important;
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
  }
}

@media print {
  .topbar,
  .sidebar,
  .reading-progress,
  .mobile-scrim,
  .copy-button,
  .hero-actions {
    display: none !important;
  }

  .site-shell {
    display: block;
    padding-top: 0;
  }

  .chapter {
    width: 100%;
    padding: 30px 0;
    break-inside: avoid;
  }

  .hero {
    min-height: 0;
  }

  .workflow-panel {
    break-inside: avoid;
  }

  body {
    color: #111;
    background: white;
    font-size: 10pt;
  }
}