:root {
  color-scheme: light;
  --paper: #fbfcff;
  --paper-alt: #f5f7fb;
  --white: #ffffff;
  --ink: #18202b;
  --navy: #0b1f3a;
  --deep-navy: #07162b;
  --muted: #5f6979;
  --divider: #d8dfea;
  --navy-divider: #2b476b;
  --purple: #5f00ff;
  --purple-soft: #8e60ff;
  --magenta: #f000c8;
  --cyan: #27bceb;
  --green: #12a66a;
  --amber: #f2a007;
  --red: #e52b25;
  --lavender: #f4f0ff;
  --pink: #fff0fb;
  --header-height: 88px;
  --header-shell: min(1420px, calc(100% - 32px));
  --reading-shell: min(1240px, calc(100% - 40px));
  --shadow-major: 0 22px 70px rgba(11, 31, 58, 0.12);
  --shadow-card: 0 12px 35px rgba(11, 31, 58, 0.075);
  --sans: Inter, ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  --mono: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--header-height) + 42px);
}

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.62;
  text-rendering: optimizeLegibility;
}

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

button,
a {
  -webkit-tap-highlight-color: transparent;
}

a {
  color: inherit;
}

img {
  display: block;
  max-width: 100%;
}

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

code {
  font-size: 0.92em;
}

.sr-only {
  position: absolute;
  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;
  z-index: 1000;
  top: 12px;
  left: 12px;
  padding: 10px 14px;
  border-radius: 9px;
  background: var(--deep-navy);
  color: var(--white);
  font-weight: 800;
  transform: translateY(-180%);
  transition: transform 160ms ease;
}

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

:where(a, button, summary, [tabindex]):focus-visible {
  outline: 3px solid var(--magenta);
  outline-offset: 4px;
}

.progress-track {
  position: fixed;
  z-index: 1200;
  inset: 0 0 auto;
  height: 3px;
  background: transparent;
  pointer-events: none;
}

.progress-bar,
#reading-progress {
  width: 0;
  height: 100%;
  background: linear-gradient(90deg, var(--purple), var(--magenta), var(--cyan));
  transform-origin: left center;
}

.ambient-field {
  position: fixed;
  z-index: -1;
  inset: 0;
  pointer-events: none;
  background:
    radial-gradient(circle at 13% 20%, rgba(39, 188, 235, 0.08), transparent 28%),
    radial-gradient(circle at 88% 32%, rgba(95, 0, 255, 0.07), transparent 30%),
    linear-gradient(115deg, transparent 0 48%, rgba(39, 188, 235, 0.025) 48% 48.2%, transparent 48.2% 100%);
}

.site-header {
  position: sticky;
  z-index: 900;
  top: 0;
  height: var(--header-height);
  border-bottom: 1px solid rgba(216, 223, 234, 0.9);
  background: rgba(251, 252, 255, 0.92);
  box-shadow: 0 9px 30px rgba(11, 31, 58, 0.055);
  backdrop-filter: blur(16px);
}

.header-shell {
  width: var(--header-shell);
  height: 100%;
  margin-inline: auto;
  display: flex;
  align-items: stretch;
  gap: 18px;
  min-width: 0;
}

.header-brand {
  flex: 0 0 54px;
  display: grid;
  place-items: center;
  text-decoration: none;
}

.header-brand img {
  width: auto;
  height: 46px;
  max-height: 46px;
}

.discipline-nav {
  flex: 1 1 auto;
  min-width: 0;
  display: flex;
  align-items: stretch;
  gap: 24px;
  overflow-x: auto;
  scrollbar-width: none;
}

.discipline-nav::-webkit-scrollbar {
  display: none;
}

.discipline-nav a {
  position: relative;
  flex: 0 0 auto;
  display: flex;
  align-items: center;
  min-height: 44px;
  color: var(--navy);
  font-size: 14px;
  font-weight: 760;
  text-decoration: none;
  white-space: nowrap;
}

.discipline-nav a[aria-current="page"]::after {
  content: "";
  position: absolute;
  right: 0;
  bottom: 15px;
  left: 0;
  height: 3px;
  border-radius: 99px;
  background: linear-gradient(90deg, var(--purple), var(--magenta));
  transform: scaleX(1);
}

.discipline-nav .featured {
  color: var(--purple);
}

.guide-main {
  display: block;
}

.shell {
  width: var(--reading-shell);
  margin-inline: auto;
}

.hero {
  position: relative;
  padding: clamp(68px, 8vw, 112px) 0 clamp(72px, 8vw, 118px);
  background:
    radial-gradient(circle at 12% 16%, rgba(39, 188, 235, 0.12), transparent 27%),
    radial-gradient(circle at 89% 24%, rgba(95, 0, 255, 0.1), transparent 30%),
    linear-gradient(180deg, var(--white), var(--paper));
}

.hero-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.2fr) minmax(300px, 0.8fr);
  align-items: start;
  gap: clamp(36px, 6vw, 84px);
}

.eyebrow,
.block-kicker,
.card-kicker,
.chapter-index,
.lab-label,
.readout-label {
  margin: 0 0 14px;
  color: var(--purple);
  font-size: 12px;
  font-weight: 900;
  letter-spacing: 0.11em;
  line-height: 1.3;
  text-transform: uppercase;
}

.hero h1 {
  max-width: 900px;
  margin: 0;
  color: var(--navy);
  font-size: clamp(48px, 6vw, 80px);
  font-weight: 860;
  letter-spacing: -0.042em;
  line-height: 1.02;
}

.hero h1 .accent {
  color: var(--purple);
}

.hero-lead {
  max-width: 780px;
  margin: 26px 0 0;
  color: #43516a;
  font-size: clamp(18px, 2vw, 21px);
  line-height: 1.6;
}

.outcomes {
  display: grid;
  gap: 9px;
  margin: 28px 0 0;
  padding: 0;
  list-style: none;
}

.outcomes li {
  position: relative;
  padding-left: 24px;
  color: var(--navy);
  font-weight: 690;
}

.outcomes li::before {
  content: "";
  position: absolute;
  top: 0.67em;
  left: 0;
  width: 9px;
  height: 9px;
  border-radius: 3px;
  background: var(--cyan);
  box-shadow: 0 0 0 5px rgba(39, 188, 235, 0.11);
}

.scope-note,
.jargon-hint,
.assumption-note {
  margin: 24px 0 0;
  padding: 14px 16px;
  border-left: 4px solid var(--amber);
  border-radius: 0 12px 12px 0;
  background: rgba(242, 160, 7, 0.08);
  color: #4d5361;
  font-size: 14px;
}

.source-note {
  margin: 18px 0 0;
  padding-top: 14px;
  border-top: 1px solid var(--divider);
  color: var(--muted);
  font-size: 13px;
}

.source-note a {
  color: var(--purple);
  font-weight: 760;
  text-underline-offset: 3px;
}

.coverage-map {
  padding: clamp(22px, 3vw, 34px);
  border: 1px solid var(--divider);
  border-radius: 24px;
  background: rgba(255, 255, 255, 0.88);
  box-shadow: var(--shadow-major);
}

.coverage-map h2,
.coverage-map h3 {
  margin: 0 0 18px;
  color: var(--navy);
  font-size: 25px;
  line-height: 1.15;
}

.coverage-map ol,
.coverage-map ul {
  display: grid;
  gap: 8px;
  margin: 0;
  padding: 0;
  list-style: none;
}

.coverage-map a {
  display: grid;
  grid-template-columns: 34px minmax(0, 1fr) auto;
  align-items: center;
  gap: 10px;
  min-height: 48px;
  padding: 8px 10px;
  border-radius: 10px;
  color: var(--navy);
  font-weight: 760;
  text-decoration: none;
}

.coverage-map a strong,
.coverage-map a small {
  min-width: 0;
}

.coverage-map a small {
  color: var(--muted);
  font-size: 11px;
  font-weight: 650;
  line-height: 1.35;
}

.coverage-map a:hover,
.coverage-map a[aria-current="location"] {
  background: var(--lavender);
  color: var(--purple);
}

.coverage-map .map-index {
  color: var(--purple);
  font-family: var(--mono);
  font-size: 12px;
}

.series-wrap {
  margin-top: clamp(46px, 6vw, 76px);
}

.series-rail {
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: 10px;
  padding: 10px;
  border: 1px solid var(--divider);
  border-radius: 18px;
  background: rgba(255, 255, 255, 0.87);
  box-shadow: var(--shadow-card);
}

.series-rail a {
  display: grid;
  align-content: center;
  min-height: 68px;
  padding: 12px;
  border: 1px solid transparent;
  border-radius: 12px;
  color: var(--navy);
  text-decoration: none;
}

.series-rail a:hover {
  border-color: var(--purple-soft);
  background: var(--lavender);
}

.series-rail a[aria-current="page"] {
  border-color: var(--purple);
  background: var(--deep-navy);
  color: var(--white);
  box-shadow: inset 0 3px 0 var(--magenta);
}

.series-rail small {
  color: inherit;
  font-size: 11px;
  font-weight: 900;
  letter-spacing: 0.08em;
  opacity: 0.68;
  text-transform: uppercase;
}

.series-rail strong {
  margin-top: 4px;
  font-size: 14px;
  line-height: 1.25;
}

.system-explorer {
  margin-top: clamp(40px, 6vw, 72px);
  padding: clamp(22px, 4vw, 42px);
  border: 1px solid var(--divider);
  border-radius: 24px;
  background: var(--white);
  box-shadow: var(--shadow-major);
}

.system-explorer h2,
.system-explorer h3 {
  margin: 0;
  color: var(--navy);
}

.system-map,
.process-rail,
.state-rail,
.timeline {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(145px, 1fr));
  gap: 12px;
  min-width: 0;
  margin-top: 24px;
}

.system-node,
.process-step,
.state-node,
.timeline-step {
  position: relative;
  min-width: 0;
  padding: 18px;
  border: 1px solid var(--divider);
  border-radius: 14px;
  background: var(--paper-alt);
}

.system-node::after,
.process-step::after,
.timeline-step::after {
  content: "→";
  position: absolute;
  top: 50%;
  right: -12px;
  z-index: 2;
  color: var(--purple);
  font-weight: 900;
  transform: translate(50%, -50%);
}

.system-node:last-child::after,
.process-step:last-child::after,
.timeline-step:last-child::after {
  content: none;
}

.system-node span,
.process-step span,
.state-node span,
.timeline-step span {
  display: block;
  color: var(--muted);
  font-size: 11px;
  font-weight: 850;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.system-node strong,
.process-step strong,
.state-node strong,
.timeline-step strong {
  display: block;
  margin-top: 7px;
  color: var(--navy);
  font-size: 16px;
  line-height: 1.3;
}

.chapter {
  padding: clamp(82px, 8vw, 120px) 0;
  background: var(--white);
  scroll-margin-top: calc(var(--header-height) + 34px);
}

.chapter.alt {
  background: var(--paper-alt);
}

.chapter.dark {
  background:
    radial-gradient(circle at 82% 18%, rgba(95, 0, 255, 0.2), transparent 28%),
    radial-gradient(circle at 15% 72%, rgba(39, 188, 235, 0.13), transparent 30%),
    var(--deep-navy);
  color: #dce8f8;
}

.chapter.dark :is(
  .eyebrow,
  .block-kicker,
  .card-kicker,
  .chapter-index,
  .lab-label,
  .readout-label,
  .question-type
) {
  color: #c8b6ff;
}

.chapter-grid {
  display: grid;
  grid-template-columns: 136px minmax(0, 1fr);
  gap: clamp(30px, 5vw, 70px);
}

.chapter-index {
  position: sticky;
  top: calc(var(--header-height) + 38px);
  align-self: start;
  margin-top: 9px;
}

.chapter-index span,
.chapter-index small {
  display: block;
}

.chapter-index span {
  color: var(--purple);
  font-family: var(--mono);
  font-size: 18px;
}

.chapter-index small {
  margin-top: 4px;
  color: var(--muted);
  font-size: 11px;
  font-weight: 850;
  letter-spacing: 0.08em;
  line-height: 1.35;
  text-transform: uppercase;
}

.chapter-content {
  min-width: 0;
}

.chapter-content > :not(:first-child) {
  margin-top: 48px;
}

.chapter-content > .content-stack {
  margin-top: 54px;
}

.chapter-heading h2,
.chapter-content > h2 {
  max-width: 900px;
  margin: 0;
  color: var(--navy);
  font-size: clamp(38px, 4.5vw, 58px);
  font-weight: 850;
  letter-spacing: -0.035em;
  line-height: 1.06;
}

.dark .chapter-heading h2,
.dark .chapter-content > h2 {
  color: var(--white);
}

.chapter-lead {
  max-width: 820px;
  margin: 22px 0 0;
  color: #58667a;
  font-size: clamp(18px, 2vw, 21px);
}

.dark .chapter-lead {
  color: #b8c9df;
}

.content-stack {
  display: grid;
  gap: 62px;
  margin-top: 54px;
}

.block-grid,
.card-grid,
.lab-grid,
.readout-grid,
.metric-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 18px;
  min-width: 0;
}

.block-grid.three,
.card-grid.three,
.metric-grid.three {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.info-card,
.concept-card,
.evidence-card,
.formula-card {
  min-width: 0;
  padding: 24px;
  border: 1px solid var(--divider);
  border-radius: 16px;
  color: var(--ink);
  background: var(--white);
  box-shadow: var(--shadow-card);
}

.chapter.dark :is(.info-card, .concept-card, .evidence-card, .formula-card)
  :is(.eyebrow, .block-kicker, .card-kicker, .lab-label, .readout-label) {
  color: var(--purple);
}

.alt .info-card,
.alt .concept-card,
.alt .evidence-card,
.alt .formula-card {
  background: rgba(255, 255, 255, 0.94);
}

.info-card.accent-cyan,
.concept-card.accent-cyan {
  border-top: 5px solid var(--cyan);
}

.info-card.accent-purple,
.concept-card.accent-purple {
  border-top: 5px solid var(--purple);
}

.info-card.accent-amber,
.concept-card.accent-amber {
  border-top: 5px solid var(--amber);
}

.info-card.accent-green,
.concept-card.accent-green {
  border-top: 5px solid var(--green);
}

.info-card.accent-red,
.concept-card.accent-red {
  border-top: 5px solid var(--red);
}

.info-card h3,
.concept-card h3,
.evidence-card h3,
.formula-card h3 {
  margin: 0;
  color: var(--navy);
  font-size: 24px;
  line-height: 1.2;
}

.info-card p:last-child,
.concept-card p:last-child,
.evidence-card p:last-child,
.formula-card p:last-child {
  margin-bottom: 0;
}

.card-list,
.contract-list,
.proof-list {
  display: grid;
  gap: 10px;
  margin: 18px 0 0;
  padding-left: 20px;
}

.lab-card {
  min-width: 0;
  padding: clamp(22px, 4vw, 42px);
  border: 1px solid var(--divider);
  border-radius: 24px;
  background: var(--white);
  box-shadow: var(--shadow-major);
}

.dark .lab-card {
  border-color: var(--navy-divider);
  background: rgba(8, 29, 55, 0.94);
  box-shadow: 0 26px 80px rgba(0, 0, 0, 0.28);
}

.lab-head {
  display: flex;
  align-items: start;
  justify-content: space-between;
  gap: 24px;
}

.lab-head h3,
.lab-card > h3 {
  max-width: 780px;
  margin: 0;
  color: var(--navy);
  font-size: clamp(28px, 3vw, 40px);
  font-weight: 830;
  letter-spacing: -0.025em;
  line-height: 1.12;
}

.dark .lab-head h3,
.dark .lab-card > h3 {
  color: var(--white);
}

.lab-intro {
  max-width: 800px;
  margin: 14px 0 0;
  color: var(--muted);
  font-size: 17px;
}

.dark .lab-intro {
  color: #b8c9df;
}

.reset-button,
.reset-control,
.small-button {
  flex: 0 0 auto;
  min-height: 42px;
  padding: 9px 15px;
  border: 1px solid var(--purple-soft);
  border-radius: 10px;
  background: var(--white);
  color: var(--purple);
  cursor: pointer;
  font-size: 13px;
  font-weight: 850;
}

.reset-button:hover,
.reset-control:hover,
.small-button:hover {
  background: var(--lavender);
}

.lab-controls {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 12px;
  margin-top: 20px;
}

.lab-controls p {
  flex: 1 1 360px;
  margin: 0;
  color: var(--muted);
  font-size: 13px;
}

.lab-status {
  margin: 18px 0 0;
  padding: 11px 13px;
  border-left: 3px solid var(--green);
  border-radius: 0 9px 9px 0;
  color: var(--navy);
  background: rgba(18, 166, 106, 0.08);
  font-size: 13px;
  font-weight: 690;
}

.choice-rail,
.scenario-rail,
.step-rail,
[data-choice-group] {
  display: flex;
  gap: 10px;
  margin-top: 26px;
  padding: 4px;
  overflow-x: auto;
  scrollbar-width: thin;
}

.choice-rail button,
.scenario-rail button,
.step-rail button,
[data-choice-group] button {
  flex: 1 0 138px;
  min-height: 52px;
  padding: 10px 14px;
  border: 1px solid var(--divider);
  border-radius: 11px;
  background: var(--paper-alt);
  color: var(--navy);
  cursor: pointer;
  font-size: 14px;
  font-weight: 800;
  line-height: 1.25;
  transition: transform 170ms ease, border-color 170ms ease, background 170ms ease;
}

.choice-rail button:hover,
.scenario-rail button:hover,
.step-rail button:hover,
[data-choice-group] button:hover {
  border-color: var(--purple-soft);
  background: var(--lavender);
  transform: translateY(-2px);
}

.choice-rail button[aria-pressed="true"],
.scenario-rail button[aria-pressed="true"],
.step-rail button[aria-pressed="true"],
[data-choice-group] button[aria-pressed="true"],
.choice-rail button[aria-selected="true"],
[data-choice-group] button[aria-selected="true"] {
  border-color: var(--deep-navy);
  background: var(--deep-navy);
  color: var(--white);
  box-shadow: inset 0 3px 0 var(--magenta);
}

.lab-stage {
  display: grid;
  grid-template-columns: minmax(0, 1.15fr) minmax(280px, 0.85fr);
  gap: 18px;
  margin-top: 24px;
  min-width: 0;
}

.lab-visual,
.diagram-panel,
.wave-panel,
.code-panel,
.lab-readout {
  min-width: 0;
  padding: 22px;
  border: 1px solid var(--divider);
  border-radius: 16px;
  background: var(--paper-alt);
}

.lab-readout {
  border-left: 5px solid var(--cyan);
  background: var(--white);
}

.dark .lab-visual,
.dark .diagram-panel,
.dark .wave-panel,
.dark .code-panel,
.dark .lab-readout {
  border-color: var(--navy-divider);
  background: #081d37;
}

.lab-readout h4,
.lab-visual h4,
.diagram-panel h4 {
  margin: 0;
  color: var(--navy);
  font-size: 22px;
  line-height: 1.25;
}

.dark .lab-readout h4,
.dark .lab-visual h4,
.dark .diagram-panel h4 {
  color: var(--white);
}

.lab-readout p {
  margin-bottom: 0;
}

.readout-grid {
  margin-top: 18px;
}

.readout-grid > div,
.metric-grid > div {
  min-width: 0;
  padding: 14px;
  border: 1px solid var(--divider);
  border-radius: 12px;
  background: rgba(255, 255, 255, 0.76);
}

.dark .readout-grid > div,
.dark .metric-grid > div {
  border-color: var(--navy-divider);
  background: rgba(7, 22, 43, 0.7);
}

.readout-grid dt,
.metric-grid dt {
  color: var(--muted);
  font-size: 11px;
  font-weight: 900;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.readout-grid dd,
.metric-grid dd {
  margin: 6px 0 0;
  color: var(--navy);
  font-weight: 720;
  line-height: 1.45;
}

.dark .readout-grid dd,
.dark .metric-grid dd {
  color: var(--white);
}

.status-pill,
.tag {
  display: inline-flex;
  align-items: center;
  min-height: 26px;
  padding: 4px 9px;
  border-radius: 99px;
  background: var(--lavender);
  color: var(--purple);
  font-size: 11px;
  font-weight: 900;
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

.status-pill.success,
.tag.success {
  background: rgba(18, 166, 106, 0.12);
  color: #087d4e;
}

.status-pill.warning,
.tag.warning {
  background: rgba(242, 160, 7, 0.14);
  color: #9a5b00;
}

.status-pill.unsafe,
.tag.unsafe {
  background: rgba(229, 43, 37, 0.12);
  color: #b51c17;
}

.scroll-surface,
.table-scroll,
.wave-scroll,
.dense-scroller {
  max-width: 100%;
  overflow-x: auto;
  border-radius: 14px;
  scrollbar-width: thin;
}

.scroll-surface:focus-visible,
.table-scroll:focus-visible,
.wave-scroll:focus-visible,
.dense-scroller:focus-visible {
  outline-offset: 2px;
}

.waveform,
.wave-grid {
  min-width: 560px;
  padding: 24px;
  border: 1px solid var(--navy-divider);
  border-radius: 14px;
  background:
    linear-gradient(rgba(39, 188, 235, 0.055) 1px, transparent 1px),
    linear-gradient(90deg, rgba(39, 188, 235, 0.055) 1px, transparent 1px),
    #07182e;
  background-size: 28px 28px;
  color: #dce8f8;
}

.wave-row {
  display: grid;
  grid-template-columns: 126px minmax(390px, 1fr);
  align-items: center;
  gap: 16px;
  min-height: 54px;
  border-bottom: 1px solid rgba(43, 71, 107, 0.7);
}

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

.wave-row > strong {
  color: #dce8f8;
  font-size: 13px;
}

.wave-track {
  position: relative;
  height: 34px;
}

.wave-track::before {
  content: "";
  position: absolute;
  top: 50%;
  right: 0;
  left: 0;
  height: 3px;
  border-radius: 99px;
  background: var(--cyan);
  box-shadow: 0 0 12px rgba(39, 188, 235, 0.45);
}

.wave-track.event::before {
  background: linear-gradient(90deg, transparent 0 18%, var(--magenta) 18% 25%, transparent 25% 100%);
}

.wave-track.warning::before {
  background: var(--amber);
}

.wave-track.success::before {
  background: var(--green);
}

pre {
  max-width: 100%;
  margin: 0;
  padding: 22px;
  overflow-x: auto;
  border: 1px solid #294668;
  border-radius: 14px;
  background: #07182e;
  color: #dce8f8;
  font-size: 14px;
  line-height: 1.55;
  tab-size: 2;
}

pre code {
  color: inherit;
  font-size: inherit;
}

.tok-comment {
  color: #9ab0c9;
}

.tok-keyword {
  color: #ff7adf;
}

.tok-type {
  color: #62dcff;
}

.tok-function {
  color: #ffd071;
}

.tok-number {
  color: #c7a8ff;
}

.tok-string {
  color: #7ce6ae;
}

.tok-constant {
  color: #ffad6a;
}

.formula {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 7px 11px;
  margin-top: 18px;
  color: var(--navy);
  font-family: var(--mono);
  font-size: clamp(17px, 2vw, 22px);
  font-weight: 760;
}

.dark .formula {
  color: var(--white);
}

table {
  width: 100%;
  min-width: 780px;
  border-collapse: separate;
  border-spacing: 0;
  border: 1px solid var(--divider);
  border-radius: 14px;
  background: var(--white);
  color: var(--ink);
}

th,
td {
  padding: 14px 16px;
  border-right: 1px solid var(--divider);
  border-bottom: 1px solid var(--divider);
  text-align: left;
  vertical-align: top;
}

th {
  background: var(--paper-alt);
  color: var(--navy);
  font-size: 12px;
  font-weight: 900;
  letter-spacing: 0.07em;
  text-transform: uppercase;
}

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

th:last-child,
td:last-child {
  border-right: 0;
}

.checkpoint {
  padding: clamp(22px, 3vw, 32px);
  border: 1px solid var(--divider);
  border-radius: 20px;
  background: rgba(255, 255, 255, 0.94);
  box-shadow: var(--shadow-card);
}

.dark .checkpoint {
  border-color: var(--navy-divider);
  background: rgba(8, 29, 55, 0.94);
}

.checkpoint-head {
  display: flex;
  align-items: start;
  justify-content: space-between;
  gap: 20px;
  margin-bottom: 18px;
}

.checkpoint h3 {
  margin: 0;
  color: var(--navy);
  font-size: 26px;
}

.dark .checkpoint h3 {
  color: var(--white);
}

.question-list {
  display: grid;
  gap: 10px;
}

.question-list details {
  border: 1px solid var(--divider);
  border-radius: 12px;
  background: var(--white);
}

.dark .question-list details {
  border-color: var(--navy-divider);
  background: #081d37;
}

.question-list summary {
  display: flex;
  align-items: center;
  gap: 18px;
  min-height: 54px;
  padding: 13px 16px;
  color: var(--navy);
  cursor: pointer;
  font-weight: 760;
  list-style: none;
}

.dark .question-list summary {
  color: var(--white);
}

.question-list summary::-webkit-details-marker {
  display: none;
}

.question-list summary::after {
  content: "+";
  flex: 0 0 auto;
  margin-left: auto;
  color: var(--purple);
  font-size: 23px;
  font-weight: 500;
}

.question-list details[open] summary::after {
  content: "−";
}

.chapter.dark .question-list summary::after {
  color: #c8b6ff;
}

.question-type {
  display: inline-block;
  margin-right: 8px;
  color: var(--purple);
  font-size: 11px;
  font-weight: 900;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.answer {
  padding: 0 16px 18px;
  color: #4c5869;
}

.dark .answer {
  color: #c4d3e6;
}

.answer p {
  margin: 10px 0 0;
}

.answer .signals,
.testing-note {
  padding-top: 10px;
  border-top: 1px solid var(--divider);
  color: var(--muted);
  font-size: 13px;
}

.references {
  padding: clamp(70px, 8vw, 105px) 0;
  color: var(--ink);
  background: var(--paper-alt);
}

.chapter.dark .references :is(.eyebrow, .block-kicker) {
  color: var(--purple);
}

.references h2 {
  margin: 0;
  color: var(--navy);
  font-size: clamp(34px, 4vw, 50px);
}

.references ol {
  display: grid;
  gap: 12px;
  max-width: 920px;
  margin: 28px 0 0;
  padding-left: 22px;
}

.references a {
  color: #164f8c;
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
}

.acceptance-list,
.reference-list ul {
  display: grid;
  gap: 9px;
  padding-left: 1.25rem;
}

.capstone-card {
  border-color: rgba(142, 96, 255, 0.5);
  background: rgba(255, 255, 255, 0.07);
}

.series-pagination,
.prev-next,
.guide-pager {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
  margin-top: 42px;
}

.series-pagination a,
.prev-next a,
.guide-pager a {
  display: grid;
  gap: 4px;
  min-height: 88px;
  padding: 20px;
  border: 1px solid var(--divider);
  border-radius: 16px;
  background: var(--white);
  color: var(--navy);
  text-decoration: none;
}

.series-pagination a:hover,
.prev-next a:hover,
.guide-pager a:hover {
  border-color: var(--purple-soft);
  background: var(--lavender);
}

.series-pagination small,
.prev-next small,
.guide-pager small {
  color: var(--purple);
  font-size: 11px;
  font-weight: 900;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.site-footer {
  padding: 28px 20px;
  border-top: 1px solid var(--divider);
  background: var(--white);
}

.footer-shell {
  width: var(--header-shell);
  margin-inline: auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  color: var(--muted);
  font-size: 14px;
}

.footer-brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
}

.footer-brand img {
  width: auto;
  height: 24px;
}

.term {
  border-bottom: 1px dotted currentColor;
  cursor: help;
  font-style: normal;
  text-decoration: none;
}

.term-tooltip {
  position: fixed;
  z-index: 1400;
  width: min(330px, calc(100vw - 28px));
  padding: 14px 16px;
  border: 1px solid #294668;
  border-radius: 12px;
  background: var(--deep-navy);
  box-shadow: 0 18px 50px rgba(0, 0, 0, 0.24);
  color: #dce8f8;
  font-size: 13px;
  line-height: 1.45;
}

.term-tooltip[hidden] {
  display: none;
}

.term-tooltip strong {
  display: block;
  margin-bottom: 4px;
  color: var(--cyan);
  font-size: 11px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.state-node[data-state="passed"] {
  border-color: rgba(18, 166, 106, 0.48);
  background: rgba(18, 166, 106, 0.1);
}

.state-node[data-state="active"] {
  border-color: var(--magenta);
  background: var(--deep-navy);
}

.state-node[data-state="active"] strong,
.state-node[data-state="active"] span {
  color: var(--white);
}

.lab-actions,
.lab-toolbar {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 18px;
}

@media (max-width: 1080px) {
  .series-rail {
    grid-template-columns: repeat(5, minmax(180px, 1fr));
    overflow-x: auto;
  }

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

@media (max-width: 980px) {
  .hero-grid,
  .lab-stage {
    grid-template-columns: 1fr;
  }

  .hero h1 {
    max-width: 820px;
  }
}

@media (max-width: 820px) {
  :root {
    --header-height: 68px;
  }

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

  .header-shell {
    gap: 12px;
  }

  .header-brand {
    flex-basis: 44px;
  }

  .header-brand img {
    height: 33px;
    max-height: 33px;
  }

  .discipline-nav {
    gap: 18px;
  }

  .discipline-nav a[aria-current="page"]::after {
    bottom: 10px;
  }

  .chapter {
    scroll-margin-top: calc(var(--header-height) + 26px);
  }

  .chapter-grid {
    grid-template-columns: 1fr;
    gap: 14px;
  }

  .chapter-index {
    position: static;
    margin: 0;
  }

  .system-node::after,
  .process-step::after,
  .timeline-step::after {
    content: none;
  }
}

@media (max-width: 760px) {
  :root {
    --header-shell: calc(100% - 24px);
    --reading-shell: calc(100% - 28px);
  }

  .hero {
    padding-top: 54px;
  }

  .block-grid,
  .card-grid,
  .lab-grid,
  .readout-grid,
  .metric-grid,
  .block-grid.three,
  .card-grid.three,
  .metric-grid.three {
    grid-template-columns: 1fr;
  }

  .system-map,
  .process-rail,
  .state-rail,
  .timeline {
    grid-template-columns: 1fr;
  }

  .lab-head,
  .checkpoint-head,
  .footer-shell {
    align-items: stretch;
    flex-direction: column;
  }

  .series-pagination,
  .prev-next,
  .guide-pager {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 560px) {
  :root {
    --reading-shell: calc(100% - 28px);
  }

  .discipline-nav {
    gap: 16px;
  }

  .discipline-nav a {
    font-size: 13px;
  }

  .hero h1 {
    font-size: clamp(42px, 14.5vw, 58px);
  }

  .coverage-map,
  .system-explorer,
  .lab-card,
  .checkpoint {
    padding: 20px;
    border-radius: 19px;
  }

  .choice-rail button,
  .scenario-rail button,
  .step-rail button,
  [data-choice-group] button {
    flex-basis: 156px;
  }
}

@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 (prefers-contrast: more) {
  :root {
    --divider: #8490a3;
  }

  .ambient-field {
    opacity: 0.35;
  }
}

@media print {
  .site-header,
  .progress-track,
  .ambient-field,
  .choice-rail,
  .scenario-rail,
  .step-rail,
  [data-choice-group],
  .reset-button,
  .reset-control,
  .small-button {
    display: none !important;
  }

  body {
    background: #ffffff;
    color: #000000;
  }

  .hero,
  .chapter,
  .chapter.alt,
  .chapter.dark,
  .references {
    padding: 32px 0;
    background: #ffffff;
    color: #000000;
  }

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

  .chapter-index {
    position: static;
  }

  .question-list details {
    break-inside: avoid;
  }

  .question-list details:not([open]) > *:not(summary) {
    display: block;
  }

  .lab-card,
  .info-card,
  .concept-card,
  .checkpoint,
  .lab-readout,
  .lab-visual {
    box-shadow: none;
    break-inside: avoid;
  }
}