:root {
  --teal: #173e46;
  --teal-dark: #102e34;
  --teal-soft: #dbe6e4;
  --clay: #a94f40;
  --clay-bright: #c45c3c;
  --sand: #f3ebdd;
  --paper: #fbf8f2;
  --ink: #262626;
  --muted: #6f6962;
  --gold: #d59528;
  --line: #d8d0c4;
  --white: #ffffff;
  --sidebar: 320px;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: Lato, Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 1rem;
  line-height: 1.6;
}
button, a { font: inherit; }
button { color: inherit; }
img { display: block; max-width: 100%; }
.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: 200;
  top: 0.75rem;
  left: 0.75rem;
  padding: 0.7rem 1rem;
  background: var(--white);
  color: var(--ink);
  transform: translateY(-160%);
}
.skip-link:focus { transform: translateY(0); }

.topbar {
  position: sticky;
  z-index: 100;
  top: 0;
  display: grid;
  grid-template-columns: var(--sidebar) 1fr auto;
  min-height: 78px;
  background: var(--paper);
  border-bottom: 1px solid var(--line);
}
.brand {
  display: flex;
  gap: 0.8rem;
  align-items: center;
  padding: 0 1.5rem;
  color: var(--teal);
  text-decoration: none;
  border-right: 1px solid var(--line);
}
.brand-mark {
  display: grid;
  width: 2.15rem;
  height: 2.15rem;
  flex: 0 0 auto;
  place-items: center;
  background: var(--clay);
  color: white;
  font-weight: 900;
}
.brand-text { display: grid; line-height: 1.2; }
.brand-text strong { font-size: 1rem; }
.brand-text small { margin-top: 0.18rem; color: var(--muted); font-size: 0.72rem; font-weight: 800; text-transform: uppercase; letter-spacing: 0.08em; }
.topbar-meta {
  display: flex;
  gap: 1rem;
  align-items: center;
  justify-content: flex-end;
  padding: 0 1.5rem;
  color: var(--muted);
  font-size: 0.82rem;
}
.topbar-meta strong { color: var(--teal); }
.nav-toggle { display: none; }

.course-shell { display: grid; grid-template-columns: var(--sidebar) minmax(0, 1fr); min-height: calc(100vh - 78px); }
.course-nav {
  position: sticky;
  top: 78px;
  align-self: start;
  height: calc(100vh - 78px);
  overflow-y: auto;
  background: var(--sand);
  border-right: 1px solid var(--line);
  scrollbar-width: thin;
}
.nav-intro { padding: 1.6rem 1.5rem 1.3rem; border-bottom: 1px solid var(--line); }
.nav-intro > p { margin: 0 0 1rem; color: var(--teal); font-size: 1.05rem; font-weight: 900; }
.course-progress > span { display: block; margin-bottom: 0.55rem; color: var(--muted); font-size: 0.75rem; font-weight: 800; }
.progress-track { height: 4px; background: #d4c8b6; }
.progress-track span { display: block; width: 0; height: 100%; background: var(--clay); transition: width 220ms ease; }
.lesson-map { padding: 0.75rem 0 2rem; }
.lesson-link {
  display: grid;
  grid-template-columns: 2.3rem 1fr;
  gap: 0.7rem;
  align-items: center;
  width: 100%;
  padding: 0.72rem 1.5rem;
  background: transparent;
  border: 0;
  border-left: 4px solid transparent;
  color: #4f4943;
  cursor: pointer;
  text-align: left;
}
.lesson-link:hover { background: rgba(255,255,255,0.45); color: var(--teal); }
.lesson-link:focus-visible { outline: 2px solid var(--teal); outline-offset: -3px; }
.lesson-link.active { background: var(--paper); border-left-color: var(--clay); color: var(--teal); font-weight: 900; }
.lesson-dot { color: var(--clay); font-size: 0.7rem; font-weight: 900; letter-spacing: 0.04em; }
.meeting-group { padding: 1.6rem 0 0.5rem; }
.meeting-heading { display: flex; justify-content: space-between; padding: 0 1.5rem; color: var(--teal); font-size: 0.72rem; font-weight: 900; letter-spacing: 0.08em; text-transform: uppercase; }
.meeting-group > p { margin: 0.35rem 1.5rem 0.75rem; color: var(--muted); font-size: 0.8rem; line-height: 1.4; }
.resources-group { border-top: 1px solid var(--line); }

.lesson-stage { min-width: 0; background: var(--paper); }
.lesson-stage:focus { outline: none; }
.lesson-toolbar {
  display: flex;
  justify-content: space-between;
  min-height: 78px;
  padding: 1rem clamp(1.5rem, 5vw, 5rem);
  border-bottom: 1px solid var(--line);
}
.lesson-toolbar p { margin: 0; }
.lesson-breadcrumb { color: var(--clay); font-size: 0.76rem; font-weight: 900; letter-spacing: 0.08em; text-transform: uppercase; }
.lesson-duration { color: var(--muted); font-size: 0.8rem; }
.map-button { display: none; }
.lesson-content { max-width: 1060px; min-height: calc(100vh - 250px); padding: clamp(2.8rem, 6vw, 6rem) clamp(1.5rem, 6vw, 6rem); }
.lesson-actions {
  display: flex;
  justify-content: space-between;
  max-width: 1060px;
  padding: 1.5rem clamp(1.5rem, 6vw, 6rem) 3rem;
  border-top: 1px solid var(--line);
}
.primary-action, .secondary-action, .choice-button, .reveal-button, .start-button {
  min-height: 46px;
  padding: 0.72rem 1rem;
  border: 1px solid var(--teal);
  cursor: pointer;
  font-weight: 900;
}
.primary-action, .start-button { background: var(--teal); color: white; }
.secondary-action, .reveal-button { background: transparent; color: var(--teal); }
.primary-action:hover, .start-button:hover { background: var(--teal-dark); }
.secondary-action:hover, .reveal-button:hover { background: var(--teal-soft); }
button:disabled { opacity: 0.35; cursor: not-allowed; }

.lesson-kicker { margin: 0 0 1rem; color: var(--clay); font-size: 0.78rem; font-weight: 900; letter-spacing: 0.1em; text-transform: uppercase; }
.lesson-title { max-width: 920px; margin: 0; font-size: clamp(2.7rem, 6vw, 6.2rem); line-height: 0.96; letter-spacing: -0.055em; }
.lesson-lead { max-width: 820px; margin: 2rem 0 0; color: #514b45; font-size: clamp(1.2rem, 2.1vw, 1.65rem); line-height: 1.5; }
.lesson-section { margin-top: clamp(3rem, 6vw, 5.5rem); }
.lesson-section h2 { max-width: 780px; margin: 0 0 1.2rem; color: var(--teal); font-size: clamp(1.8rem, 3.5vw, 3.2rem); line-height: 1.12; letter-spacing: -0.035em; }
.lesson-section h3 { margin: 2rem 0 0.7rem; font-size: 1.25rem; }
.lesson-section p, .lesson-section li { max-width: 820px; color: #5b554f; font-size: 1.04rem; }
.lesson-section ul, .lesson-section ol { padding-left: 1.35rem; }
.lesson-section li { margin-bottom: 0.55rem; }
.opening-grid { display: grid; grid-template-columns: 1.2fr 0.8fr; gap: clamp(2rem, 5vw, 5rem); align-items: end; }
.opening-visual { position: relative; overflow: hidden; background: #e9dfcf; aspect-ratio: 4 / 3; }
.opening-visual img { width: 100%; height: 100%; object-fit: cover; }
.opening-visual figcaption { position: absolute; right: 0; bottom: 0; max-width: 28rem; padding: 0.9rem 1.1rem; background: var(--teal); color: white; font-size: 0.82rem; }
.facts-row { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1px; margin-top: 4rem; background: var(--line); border: 1px solid var(--line); }
.fact { padding: 1.4rem; background: var(--sand); }
.fact strong { display: block; color: var(--teal); font-size: 1.35rem; }
.fact span { color: var(--muted); font-size: 0.82rem; }

.movement-line { display: grid; grid-template-columns: repeat(5, 1fr); margin: 2.2rem 0 0; padding: 0; list-style: none; }
.movement-line li { position: relative; padding-top: 2.1rem; color: var(--teal); font-size: 0.82rem; font-weight: 900; text-align: center; }
.movement-line li::before { position: absolute; z-index: 1; top: 0; left: 50%; width: 1rem; height: 1rem; border-radius: 50%; background: var(--clay); content: ""; transform: translateX(-50%); }
.movement-line li::after { position: absolute; top: 0.48rem; left: 50%; width: 100%; height: 1px; background: var(--line); content: ""; }
.movement-line li:last-child::after { display: none; }
.course-meetings { display: grid; grid-template-columns: 1fr 1fr; gap: 3rem; margin-top: 3.5rem; }
.meeting-summary { padding-top: 1.3rem; border-top: 4px solid var(--clay); }
.meeting-summary p { color: var(--muted); }
.meeting-summary h2 { margin: 0.5rem 0 0.8rem; color: var(--ink); font-size: 2rem; line-height: 1.15; }
.meeting-summary button { margin-top: 0.8rem; }

.chat-prompt { margin: 2.5rem 0; padding: 1.5rem 0 1.5rem 2rem; border-left: 5px solid var(--gold); }
.chat-prompt span { display: block; margin-bottom: 0.35rem; color: var(--clay); font-size: 0.74rem; font-weight: 900; letter-spacing: 0.09em; text-transform: uppercase; }
.chat-prompt p { margin: 0; color: var(--ink); font-size: clamp(1.3rem, 2.6vw, 2rem); line-height: 1.35; }
.concept-equation { display: grid; grid-template-columns: 1fr auto 1fr; gap: 1.5rem; align-items: stretch; margin-top: 2.5rem; }
.concept-side { padding: 1.8rem; background: var(--sand); border-top: 5px solid var(--teal); }
.concept-side:last-child { border-top-color: var(--clay); }
.concept-side strong { display: block; margin-bottom: 0.45rem; font-size: 1.35rem; }
.concept-plus { align-self: center; color: var(--clay); font-size: 2.6rem; font-weight: 300; }
.impact-locations, .criteria-grid, .evidence-grid, .record-grid, .credit-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 1px; margin-top: 2rem; background: var(--line); border: 1px solid var(--line); }
.info-cell { min-height: 150px; padding: 1.4rem; background: var(--paper); }
.info-cell .cell-number { color: var(--clay); font-size: 0.75rem; font-weight: 900; }
.info-cell h3 { margin: 0.6rem 0; color: var(--teal); }
.info-cell p { margin: 0; font-size: 0.96rem; }
.criteria-grid .info-cell { background: white; }
.criterion-question { margin-top: 0.8rem !important; color: var(--clay) !important; font-weight: 800; }
.attention-list { display: grid; gap: 0; margin-top: 2rem; border-top: 1px solid var(--line); }
.attention-item { display: grid; grid-template-columns: 2.5rem 0.7fr 1.3fr; gap: 1rem; padding: 1.1rem 0; border-bottom: 1px solid var(--line); }
.attention-item span { color: var(--clay); font-size: 0.75rem; font-weight: 900; }
.attention-item strong { color: var(--teal); }

.case-box { margin-top: 2.5rem; padding: clamp(1.5rem, 4vw, 3rem); background: var(--sand); border-top: 6px solid var(--clay); }
.case-label { margin: 0; color: var(--clay); font-size: 0.74rem; font-weight: 900; letter-spacing: 0.09em; text-transform: uppercase; }
.case-box h2 { margin: 0.5rem 0 1rem; color: var(--ink); }
.choice-group { display: flex; flex-wrap: wrap; gap: 0.7rem; margin-top: 1.5rem; }
.choice-button { min-width: 9rem; background: white; color: var(--teal); }
.choice-button:hover, .choice-button.selected { background: var(--teal); color: white; }
.answer-panel { display: none; margin-top: 1.5rem; padding-top: 1.5rem; border-top: 1px solid #cbbfac; }
.answer-panel.visible { display: block; }
.answer-panel strong { color: var(--teal); }
.evidence-flow { display: grid; grid-template-columns: repeat(4, 1fr); gap: 1px; margin-top: 2rem; background: var(--line); border: 1px solid var(--line); }
.evidence-step { min-height: 185px; padding: 1.3rem; background: var(--paper); }
.evidence-step span { color: var(--clay); font-size: 0.75rem; font-weight: 900; }
.evidence-step strong { display: block; margin: 0.55rem 0; color: var(--teal); }
.evidence-step p { margin: 0; font-size: 0.92rem; }

.compare-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 2.5rem; margin-top: 2rem; }
.compare-panel { padding-top: 1.2rem; border-top: 4px solid var(--teal); }
.compare-panel.caution { border-top-color: var(--clay); }
.compare-panel h3 { margin-top: 0; color: var(--teal); }
.do-list { padding: 0; list-style: none; }
.do-list li { position: relative; padding: 0.7rem 0 0.7rem 1.8rem; border-bottom: 1px solid var(--line); }
.do-list li::before { position: absolute; left: 0; color: var(--clay); content: "✓"; font-weight: 900; }
.caution .do-list li::before { content: "×"; }
.interview-flow { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1px; margin-top: 2rem; background: var(--line); border: 1px solid var(--line); }
.interview-step { padding: 1.2rem; background: var(--paper); }
.interview-step span { color: var(--clay); font-size: 0.72rem; font-weight: 900; }
.interview-step strong { display: block; margin-top: 0.3rem; color: var(--teal); }
.question-contrast { display: grid; grid-template-columns: 1fr 1fr; gap: 2rem; margin-top: 2rem; }
.question-example { padding: 1.5rem; background: var(--sand); }
.question-example.good { background: var(--teal-soft); }
.question-example span { color: var(--clay); font-size: 0.74rem; font-weight: 900; text-transform: uppercase; }
.question-example blockquote { margin: 0.7rem 0 0; font-size: 1.2rem; line-height: 1.4; }
.practice-brief { display: grid; grid-template-columns: 0.35fr 1fr; gap: 2.5rem; margin-top: 2.5rem; }
.practice-time { color: var(--clay); font-size: clamp(2.8rem, 6vw, 5.5rem); font-weight: 900; line-height: 0.9; }
.practice-time small { display: block; color: var(--muted); font-size: 0.78rem; letter-spacing: 0.08em; text-transform: uppercase; }
.practice-steps { margin: 0; padding-left: 1.3rem; }
.practice-steps li { margin-bottom: 1rem; padding-left: 0.4rem; }

.observation-example { display: grid; grid-template-columns: 1fr 1fr; gap: 1px; margin-top: 2rem; background: var(--line); border: 1px solid var(--line); }
.observation-card { padding: 1.6rem; background: var(--paper); }
.observation-card:first-child { border-top: 5px solid var(--teal); }
.observation-card:last-child { border-top: 5px solid var(--clay); }
.observation-card span { color: var(--clay); font-size: 0.74rem; font-weight: 900; text-transform: uppercase; }
.observation-card blockquote { margin: 0.8rem 0; font-size: 1.1rem; line-height: 1.5; }
.source-triangle { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1px; margin-top: 2rem; background: var(--line); border: 1px solid var(--line); }
.source-triangle div { padding: 1.5rem; background: var(--sand); color: var(--teal); font-weight: 900; text-align: center; }
.flow-list { display: grid; grid-template-columns: repeat(5, 1fr); gap: 1px; margin-top: 2rem; background: var(--line); border: 1px solid var(--line); }
.flow-list div { min-height: 130px; padding: 1rem; background: var(--paper); }
.flow-list span { color: var(--clay); font-size: 0.72rem; font-weight: 900; }
.flow-list strong { display: block; margin-top: 0.4rem; color: var(--teal); line-height: 1.25; }
.scope-note { margin-top: 2rem; padding: 1.2rem 0; border-top: 1px solid var(--clay); border-bottom: 1px solid var(--clay); color: #554f49; }

.instrument-header { display: grid; grid-template-columns: 1fr 0.75fr; gap: 3rem; align-items: center; }
.instrument-header img { width: 100%; aspect-ratio: 4 / 3; object-fit: cover; }
.instrument-status { display: inline-block; margin-bottom: 1rem; padding: 0.25rem 0.55rem; background: var(--sand); color: var(--clay); font-size: 0.72rem; font-weight: 900; text-transform: uppercase; }
.question-list { margin: 2rem 0 0; padding: 0; list-style: none; counter-reset: questions; }
.question-list li { display: grid; grid-template-columns: 3rem 1fr; gap: 1rem; padding: 1.2rem 0; border-bottom: 1px solid var(--line); counter-increment: questions; }
.question-list li::before { color: var(--clay); content: counter(questions, decimal-leading-zero); font-size: 0.76rem; font-weight: 900; }
.question-list strong { display: block; color: var(--teal); }
.question-list p { margin: 0.3rem 0 0; font-size: 0.92rem; }
.field-note { margin-top: 2rem; padding: 1.5rem; background: var(--teal); color: white; }
.field-note p { margin: 0; color: white; }

.site-footer {
  display: grid;
  grid-template-columns: var(--sidebar) 1fr;
  min-height: 130px;
  background: var(--teal-dark);
  color: white;
}
.site-footer > div:first-child { display: grid; align-content: center; padding: 1.5rem; border-right: 1px solid rgba(255,255,255,0.15); }
.site-footer > div:first-child span { color: #bacdca; font-size: 0.82rem; }
.footer-partners { display: grid; align-content: center; gap: 0.3rem; padding: 1.5rem clamp(1.5rem, 5vw, 5rem); color: #c9d5d3; font-size: 0.8rem; }

@media (max-width: 1100px) {
  :root { --sidebar: 285px; }
  .lesson-content { padding-right: 3rem; padding-left: 3rem; }
  .lesson-actions { padding-right: 3rem; padding-left: 3rem; }
  .evidence-flow, .flow-list { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 820px) {
  .topbar { grid-template-columns: 1fr auto; min-height: 68px; }
  .brand { border-right: 0; }
  .topbar-meta { display: none; }
  .nav-toggle { display: grid; width: 68px; place-content: center; gap: 6px; background: transparent; border: 0; }
  .nav-toggle span:not(.sr-only) { display: block; width: 24px; height: 2px; background: var(--ink); }
  .course-shell { grid-template-columns: 1fr; }
  .course-nav { position: fixed; z-index: 90; top: 68px; bottom: 0; left: 0; width: min(88vw, 340px); height: auto; transform: translateX(-105%); transition: transform 180ms ease; box-shadow: 18px 0 40px rgba(20,35,35,0.18); }
  .course-nav.open { transform: translateX(0); }
  .lesson-toolbar { min-height: 72px; padding: 0.85rem 1.25rem; }
  .map-button { display: block; align-self: center; padding: 0.5rem 0; background: transparent; border: 0; color: var(--teal); font-size: 0.82rem; font-weight: 900; }
  .lesson-content { min-height: 0; padding: 3.5rem 1.25rem; }
  .lesson-actions { padding: 1.25rem 1.25rem 2.5rem; }
  .site-footer { grid-template-columns: 1fr; }
  .site-footer > div:first-child { border-right: 0; border-bottom: 1px solid rgba(255,255,255,0.15); }
  .opening-grid, .course-meetings, .compare-grid, .question-contrast, .practice-brief, .instrument-header { grid-template-columns: 1fr; }
  .opening-visual { order: -1; }
  .facts-row, .concept-equation, .impact-locations, .criteria-grid, .evidence-grid, .record-grid, .credit-grid, .interview-flow, .observation-example, .source-triangle { grid-template-columns: 1fr; }
  .concept-plus { justify-self: center; }
  .attention-item { grid-template-columns: 2rem 1fr; }
  .attention-item p { grid-column: 2; margin-top: 0; }
  .movement-line { overflow-x: auto; grid-template-columns: repeat(5, minmax(110px, 1fr)); padding-bottom: 0.5rem; }
}

@media (max-width: 520px) {
  .brand { padding-left: 1rem; }
  .brand-text small { display: none; }
  .lesson-title { font-size: clamp(2.55rem, 14vw, 4rem); }
  .facts-row { grid-template-columns: 1fr; }
  .lesson-actions { gap: 0.7rem; }
  .primary-action, .secondary-action { padding: 0.7rem; font-size: 0.86rem; }
  .choice-group { display: grid; }
  .choice-button { width: 100%; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { transition-duration: 0.01ms !important; }
}