:root {
  color-scheme: light;
  --paper: #f4f5f1;
  --surface: #ffffff;
  --ink: #171c19;
  --muted: #69726d;
  --line: #dce1dc;
  --line-strong: #c6cec8;
  --accent: #176b4c;
  --accent-soft: #e2efe8;
  --danger: #9c3f32;
  --radius: 16px;
  font-family: Inter, ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-synthesis: none;
}

* {
  box-sizing: border-box;
}

html {
  background: var(--paper);
}

body {
  min-width: 320px;
  margin: 0;
  color: var(--ink);
  background: var(--paper);
  line-height: 1.5;
  text-rendering: optimizeLegibility;
}

a {
  color: inherit;
}

.site-header,
main,
footer {
  width: min(1180px, calc(100% - 48px));
  margin-inline: auto;
}

.site-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: 72px;
  border-bottom: 1px solid var(--line-strong);
}

.brand {
  font-size: 1.05rem;
  font-weight: 760;
  letter-spacing: -0.035em;
  text-decoration: none;
}

.brand::after {
  content: "";
  display: inline-block;
  width: 6px;
  height: 6px;
  margin-left: 3px;
  border-radius: 50%;
  background: var(--accent);
  vertical-align: 0.35em;
}

.site-label {
  color: var(--muted);
  font-size: 0.76rem;
  font-weight: 650;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

main {
  padding-block: 64px 88px;
}

.skip-link {
  position: absolute;
  z-index: 10;
  top: -60px;
  left: 16px;
  padding: 10px 14px;
  border-radius: 8px;
  color: var(--surface);
  background: var(--accent);
}

.skip-link:focus {
  top: 12px;
}

.site-nav {
  display: flex;
  align-items: center;
  gap: 6px;
}

.site-nav a {
  padding: 8px 12px;
  border-radius: 999px;
  color: var(--muted);
  font-size: 0.83rem;
  font-weight: 650;
  text-decoration: none;
}

.site-nav a:hover,
.site-nav a[aria-current="page"] {
  color: var(--accent);
  background: var(--accent-soft);
}

.site-nav a:focus-visible,
.intro-links a:focus-visible,
.pipeline summary:focus-visible,
.interpretation summary:focus-visible,
.interpretation a:focus-visible,
.explainer a:focus-visible {
  outline: 3px solid var(--accent);
  outline-offset: 3px;
}

.intro {
  max-width: 860px;
}

.eyebrow,
.panel-kicker {
  margin: 0 0 12px;
  color: var(--accent);
  font-size: 0.72rem;
  font-weight: 750;
  letter-spacing: 0.13em;
  text-transform: uppercase;
}

h1,
h2,
h3,
p {
  margin-top: 0;
}

h1 {
  max-width: 760px;
  margin-bottom: 22px;
  font-size: clamp(3rem, 8vw, 6.7rem);
  font-weight: 620;
  letter-spacing: -0.075em;
  line-height: 0.92;
}

.lede {
  max-width: 650px;
  margin-bottom: 18px;
  color: #4d5751;
  font-size: clamp(1.05rem, 2vw, 1.3rem);
  line-height: 1.55;
}

.intro-context {
  max-width: 640px;
  margin-bottom: 18px;
  color: var(--muted);
  font-size: 0.95rem;
}

.intro-links {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px 20px;
  margin-bottom: 38px;
}

.intro-links a {
  font-size: 0.86rem;
  font-weight: 700;
  text-decoration: none;
}

.primary-link {
  display: inline-flex;
  align-items: center;
  min-height: 42px;
  padding: 10px 15px;
  border: 1px solid var(--accent);
  border-radius: 999px;
  color: var(--surface);
  background: var(--accent);
}

.primary-link:hover {
  background: #10563c;
}

.primary-link span,
.text-link span {
  margin-left: 5px;
}

.text-link {
  color: var(--accent);
  text-underline-offset: 3px;
}

.text-link:hover {
  text-decoration: underline;
}

.controls {
  display: grid;
  grid-template-columns: minmax(0, 280px) repeat(2, minmax(0, 230px));
  gap: 16px;
  margin-bottom: 18px;
}

label span {
  display: block;
  margin-bottom: 8px;
  color: var(--muted);
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

select {
  width: 100%;
  min-height: 48px;
  padding: 0 42px 0 14px;
  border: 1px solid var(--line-strong);
  border-radius: 10px;
  color: var(--ink);
  background: var(--surface);
  font: inherit;
}

select:focus-visible {
  outline: 3px solid rgb(23 107 76 / 20%);
  outline-offset: 2px;
  border-color: var(--accent);
}

.status {
  min-height: 24px;
  margin: 0;
  color: var(--muted);
  font-size: 0.9rem;
}

.status.error {
  color: var(--danger);
}

#comparison {
  margin-top: 72px;
}

.section-heading,
.panel-heading {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 28px;
}

.section-heading {
  margin-bottom: 26px;
}

.section-heading h2 {
  margin-bottom: 0;
  font-size: clamp(2rem, 5vw, 3.5rem);
  font-weight: 590;
  letter-spacing: -0.055em;
  line-height: 1;
}

.course-meta {
  margin-bottom: 2px;
  color: var(--muted);
  font-size: 0.9rem;
  text-align: right;
}

.panel {
  margin-bottom: 18px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
}

.chart-panel {
  padding: 28px 28px 20px;
}

.panel-heading {
  align-items: center;
  margin-bottom: 26px;
}

.panel-kicker {
  margin-bottom: 5px;
  color: var(--muted);
  font-size: 0.66rem;
}

.panel-heading h3 {
  margin-bottom: 0;
  font-size: 1.25rem;
  font-weight: 650;
  letter-spacing: -0.025em;
}

.chart-direction,
.chart-caption {
  margin: 0;
  color: var(--muted);
  font-size: 0.83rem;
}

.charts-scroll {
  overflow-x: auto;
}

.charts-timeline {
  min-width: 620px;
}

.chart-block + .chart-block {
  margin-top: 28px;
  padding-top: 28px;
  border-top: 1px solid var(--line);
}

.chart-subheading {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 20px;
  margin-bottom: 8px;
}

.chart-subheading h4 {
  margin: 0;
  font-size: 0.95rem;
  font-weight: 680;
}

.chart {
  min-height: 230px;
}

.chart svg {
  display: block;
  width: 100%;
  height: auto;
}

.chart-grid {
  stroke: var(--line);
  stroke-width: 1;
}

.chart-axis-label,
.chart-year {
  fill: var(--muted);
  font-family: inherit;
  font-size: 12px;
}

.chart-path {
  fill: none;
  stroke: var(--accent);
  stroke-width: 2.5;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.chart-point,
.scatter-point {
  fill: var(--surface);
  stroke: var(--accent);
  stroke-width: 2.5;
}

.chart-point:focus,
.scatter-point:focus,
.scatter-point:hover {
  outline: none;
  fill: var(--accent-soft);
  stroke-width: 4;
}

.chart-caption {
  min-height: 20px;
  margin-top: 6px;
}

.scatter-chart {
  max-width: 760px;
  margin-inline: auto;
}

.scatter-pace-label {
  margin: 0 0 12px;
  font-size: 0.9rem;
  font-weight: 650;
}

.scatter-detail {
  min-height: 2.8em;
  margin: 12px 0 4px;
  color: var(--accent);
  font-size: 0.88rem;
  font-variant-numeric: tabular-nums;
}

.table-panel {
  overflow: hidden;
}

.table-panel .panel-heading {
  margin: 0;
  padding: 24px 28px 18px;
  border-bottom: 1px solid var(--line);
}

.table-scroll {
  overflow-x: auto;
}

table {
  width: 100%;
  min-width: 1080px;
  border-collapse: collapse;
  font-size: 0.84rem;
  font-variant-numeric: tabular-nums;
}

th,
td {
  padding: 15px 14px;
  border-bottom: 1px solid var(--line);
  text-align: right;
  white-space: nowrap;
}

th:first-child,
td:first-child {
  padding-left: 28px;
  text-align: left;
}

th:last-child,
td:last-child {
  padding-right: 28px;
}

th {
  color: var(--muted);
  background: #fafbf9;
  font-size: 0.67rem;
  font-weight: 720;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

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

tbody tr:hover {
  background: #fafbf9;
}

.edition-year {
  font-weight: 720;
}

.comparison-note {
  display: block;
  margin-top: 2px;
  color: var(--muted);
  font-size: 0.68rem;
  font-weight: 500;
}

.change-slower {
  color: #9c3f32;
}

.change-faster {
  color: var(--accent);
}

.interpretation {
  display: grid;
  grid-template-columns: 170px minmax(0, 650px);
  gap: 24px;
  margin-top: 34px;
  padding-top: 24px;
  border-top: 1px solid var(--line-strong);
}

.interpretation h3 {
  margin: 0;
  font-size: 0.82rem;
  font-weight: 720;
}

.interpretation p {
  margin: 0;
  color: var(--muted);
  font-size: 0.88rem;
}

.interpretation details {
  grid-column: 2;
  font-size: 0.88rem;
}

.interpretation summary {
  color: var(--accent);
  cursor: pointer;
}

.interpretation details p {
  margin-top: 12px;
}

.empty-state,
.noscript {
  padding: 48px 24px;
  color: var(--muted);
  text-align: center;
}

footer {
  display: flex;
  justify-content: space-between;
  gap: 24px;
  padding-block: 24px 40px;
  border-top: 1px solid var(--line-strong);
  color: var(--muted);
  font-size: 0.75rem;
}


/* The explainer shares the page's type and colour, while keeping its flow separate. */
.explainer {
  max-width: 1040px;
  padding-top: 78px;
}

.explainer-hero h1 {
  max-width: 850px;
  font-size: clamp(3.1rem, 7vw, 5.8rem);
  line-height: 0.99;
}

.explainer-hero .lede {
  max-width: 760px;
  margin-bottom: 28px;
}

.example-card {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  max-width: 840px;
  padding: 18px 0;
  border-top: 1px solid var(--line-strong);
  border-bottom: 1px solid var(--line-strong);
  font-variant-numeric: tabular-nums;
}

.example-card div,
.example-card strong {
  display: block;
}

.example-card div > strong {
  margin-top: 3px;
  font-size: 1.06rem;
}

.example-kicker {
  color: var(--muted);
  font-size: 0.74rem;
}

.example-card p {
  margin: 0;
  color: var(--accent);
  font-size: 0.84rem;
  white-space: nowrap;
}

.example-card p strong {
  display: inline;
  font-size: 1.12rem;
}

.example-note {
  max-width: 750px;
  margin: 14px 0 0;
  color: var(--muted);
  font-size: 0.85rem;
}

.journey {
  margin-top: 96px;
}

.journey-heading {
  margin-bottom: 30px;
}

.journey-heading h2 {
  margin-bottom: 10px;
  font-size: clamp(2rem, 4vw, 3.25rem);
  font-weight: 600;
  letter-spacing: -0.055em;
  line-height: 1.05;
}

.journey-heading > p:last-child {
  max-width: 650px;
  margin-bottom: 0;
  color: var(--muted);
}

.pipeline {
  display: grid;
  gap: 16px;
  margin: 0;
  padding: 0;
  list-style: none;
}

.pipeline-step {
  position: relative;
}

.pipeline-step:not(:last-child)::after {
  position: absolute;
  bottom: -16px;
  left: 31px;
  height: 16px;
  border-left: 1px solid var(--accent);
  content: "";
}

.pipeline details {
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
}

.pipeline details[open] {
  border-color: var(--line-strong);
}

.pipeline summary {
  display: grid;
  grid-template-columns: 60px minmax(0, 1fr) auto 18px;
  align-items: center;
  gap: 18px;
  min-height: 116px;
  padding: 18px 24px;
  cursor: pointer;
  list-style: none;
}

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

.pipeline summary::after {
  color: var(--accent);
  font-size: 1.35rem;
  font-weight: 400;
  line-height: 1;
  content: "+";
}

.pipeline details[open] summary::after {
  content: "−";
}

.pipeline summary:hover {
  background: #fafbf9;
}

.step-number {
  display: grid;
  place-items: center;
  width: 48px;
  height: 48px;
  border: 1px solid #c7ddcf;
  border-radius: 50%;
  color: var(--accent);
  background: var(--accent-soft);
  font-size: 0.82rem;
  font-weight: 750;
  font-variant-numeric: tabular-nums;
}

.step-main {
  display: grid;
  gap: 4px;
  min-width: 0;
}

.step-artifact {
  color: var(--accent);
  font-size: 0.69rem;
  font-weight: 730;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.step-main strong {
  font-size: 1.18rem;
  font-weight: 680;
  letter-spacing: -0.025em;
}

.step-main > span:last-child {
  color: var(--muted);
  font-size: 0.86rem;
}

.step-safeguard {
  padding: 6px 10px;
  border-radius: 999px;
  color: var(--accent);
  background: var(--accent-soft);
  font-size: 0.72rem;
  font-weight: 700;
  white-space: nowrap;
}

.step-detail {
  margin: 0 24px 0 102px;
  padding: 18px 0 22px;
  border-top: 1px solid var(--line);
}

.step-detail p {
  max-width: 710px;
  margin-bottom: 12px;
  color: #4d5751;
  font-size: 0.9rem;
}

.step-detail a {
  color: var(--accent);
  font-size: 0.84rem;
  font-weight: 690;
  text-underline-offset: 3px;
}

.explainer-notes {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 18px;
  margin-top: 64px;
}

.note-card {
  padding: 28px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
}

.note-card h2 {
  margin-bottom: 12px;
  font-size: 1.35rem;
  font-weight: 650;
  letter-spacing: -0.035em;
}

.note-card p:last-child {
  margin-bottom: 0;
  color: #4d5751;
  font-size: 0.9rem;
}

.explainer-end {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: 30px;
  margin-top: 64px;
  padding-top: 25px;
  border-top: 1px solid var(--line-strong);
}

.explainer-end p {
  max-width: 640px;
  margin-bottom: 0;
  color: var(--muted);
  font-size: 0.88rem;
}

.return-link {
  color: var(--accent);
  font-weight: 700;
  text-decoration: none;
  white-space: nowrap;
}

.return-link:hover {
  text-decoration: underline;
  text-underline-offset: 4px;
}

.page-jump {
  display: flex;
  flex-wrap: wrap;
  gap: 6px 22px;
  margin-top: 28px;
}

.page-jump a {
  padding-block: 5px;
  color: var(--accent);
  font-size: 0.82rem;
  font-weight: 700;
  text-decoration-thickness: 1px;
  text-underline-offset: 4px;
}

.design-section,
.model-section,
.proof-section {
  margin-top: 88px;
}

.decision-grid,
.proof-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 14px;
}

.decision-card,
.proof-card {
  padding: 24px 26px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
}

.decision-card-wide {
  grid-column: 1 / -1;
  background: #edf4ee;
}

.decision-number,
.proof-status {
  display: block;
  margin-bottom: 13px;
  color: var(--accent);
  font-size: 0.7rem;
  font-weight: 750;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.decision-card h3,
.proof-card h3 {
  margin-bottom: 10px;
  font-size: 1.15rem;
  font-weight: 670;
  letter-spacing: -0.035em;
  line-height: 1.25;
}

.decision-card p,
.proof-card p {
  max-width: 650px;
  margin: 0;
  color: #4d5751;
  font-size: 0.87rem;
  line-height: 1.6;
}

.model-heading {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: 30px;
  margin-bottom: 22px;
}

.model-heading h2 {
  max-width: 560px;
  margin: 0;
  font-size: clamp(1.8rem, 3.5vw, 2.8rem);
  font-weight: 600;
  letter-spacing: -0.055em;
  line-height: 1.08;
}

.model-heading > p {
  max-width: 310px;
  margin: 0;
  color: var(--muted);
  font-size: 0.82rem;
}

.model-table-scroll {
  overflow-x: auto;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
}

.model-table {
  min-width: 580px;
  font-size: 0.85rem;
}

.model-table th,
.model-table td {
  padding: 15px 20px;
  text-align: left;
  white-space: normal;
}

.model-table thead th {
  background: #edf4ee;
}

.model-table tbody th {
  width: 35%;
  background: var(--surface);
  color: var(--ink);
  font-size: 0.82rem;
  font-weight: 650;
  letter-spacing: 0;
  text-transform: none;
}

.model-table code {
  font-size: 0.82rem;
  overflow-wrap: anywhere;
}

.model-note {
  margin: 13px 0 0;
  color: var(--muted);
  font-size: 0.83rem;
}

.proof-card {
  border-top: 3px solid var(--accent);
}

.proof-card a {
  display: inline-block;
  margin-top: 17px;
  color: var(--accent);
  font-size: 0.82rem;
  font-weight: 700;
  text-underline-offset: 3px;
}

@media (max-width: 720px) {
  .site-header,
  main,
  footer {
    width: min(1180px, calc(100% - 28px));
  }

  main {
    padding-block: 64px 76px;
  }

  .site-label {
    display: none;
  }

  .site-nav a {
    padding-inline: 8px;
    font-size: 0.77rem;
  }

  .explainer {
    padding-top: 62px;
  }

  .example-card,
  .explainer-end {
    align-items: flex-start;
    flex-direction: column;
    gap: 12px;
  }

  .journey {
    margin-top: 74px;
  }

  .pipeline summary {
    grid-template-columns: 44px minmax(0, 1fr) 16px;
    gap: 10px;
    padding: 17px 15px;
  }

  .step-number {
    width: 38px;
    height: 38px;
    font-size: 0.72rem;
  }

  .step-safeguard {
    grid-column: 2;
    width: fit-content;
    margin-top: 4px;
  }

  .pipeline summary::after {
    grid-column: 3;
    grid-row: 1;
  }

  .pipeline-step:not(:last-child)::after {
    left: 23px;
  }

  .step-detail {
    margin: 0 16px 0 69px;
  }

  .decision-grid,
  .proof-grid,
  .explainer-notes {
    grid-template-columns: 1fr;
  }

  .decision-card-wide {
    grid-column: auto;
  }

  .model-heading {
    align-items: flex-start;
    flex-direction: column;
    gap: 12px;
  }

  .model-heading > p {
    max-width: 600px;
  }

  .design-section,
  .model-section,
  .proof-section {
    margin-top: 68px;
  }

  .note-card {
    padding: 22px;
  }

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

  #comparison {
    margin-top: 72px;
  }

  .section-heading,
  .panel-heading,
  .chart-subheading {
    align-items: flex-start;
    flex-direction: column;
    gap: 10px;
  }

  .course-meta {
    text-align: left;
  }

  .chart-panel {
    padding: 22px 18px 16px;
  }

  .table-panel .panel-heading {
    padding-inline: 20px;
  }

  .interpretation {
    grid-template-columns: 1fr;
    gap: 8px;
  }

  .interpretation details {
    grid-column: 1;
  }

  footer {
    align-items: flex-start;
    flex-direction: column;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    scroll-behavior: auto !important;
  }
}