:root {
  --bg: #f7fbfa;
  --surface: #ffffff;
  --surface-strong: #e7f5f1;
  --ink: #10211f;
  --muted: #58706c;
  --accent: #0f766e;
  --accent-strong: #0b534e;
  --amber: #f59e0b;
  --rose: #be123c;
  --line: #d7e7e3;
  --shadow: 0 18px 50px rgba(15, 83, 78, 0.14);
  --radius: 8px;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  overflow-x: hidden;
  background:
    radial-gradient(circle at top left, rgba(15, 118, 110, 0.12), transparent 34rem),
    linear-gradient(180deg, #f7fbfa 0%, #edf7f4 100%);
  color: var(--ink);
}

a {
  color: inherit;
}

button,
input,
select {
  font: inherit;
}

:focus-visible {
  outline: 3px solid #fbbf24;
  outline-offset: 3px;
}

.skip-link {
  left: 1rem;
  position: fixed;
  top: -5rem;
  z-index: 30;
  background: var(--ink);
  color: white;
  padding: 0.75rem 1rem;
  border-radius: var(--radius);
}

.skip-link:focus {
  top: 1rem;
}

.app-header {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  align-items: center;
  gap: 1rem;
  justify-content: space-between;
  padding: 0.9rem clamp(1rem, 4vw, 2rem);
  background: rgba(247, 251, 250, 0.9);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(18px);
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.85rem;
  min-width: 0;
  max-width: 100%;
}

.brand-mark {
  display: grid;
  place-items: center;
  flex: 0 0 2.75rem;
  width: 2.75rem;
  height: 2.75rem;
  border-radius: 50%;
  background: var(--accent);
  color: white;
  font-weight: 800;
}

.brand p,
.course-label,
.section-heading p,
.tool-panel > div > p,
.transcript-header p,
.nav-title {
  margin: 0 0 0.2rem;
  color: var(--accent-strong);
  font-size: 0.78rem;
  font-weight: 800;
  letter-spacing: 0;
  text-transform: uppercase;
}

.brand h1 {
  margin: 0;
  font-size: clamp(0.95rem, 2vw, 1.15rem);
  line-height: 1.2;
  overflow-wrap: anywhere;
}

.header-actions,
.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.65rem;
}

.primary-button,
.ghost-button,
.icon-button {
  border: 0;
  border-radius: var(--radius);
  cursor: pointer;
  min-height: 2.6rem;
}

.primary-button,
.ghost-button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.72rem 1rem;
  text-decoration: none;
  font-weight: 800;
}

.primary-button {
  background: var(--accent);
  color: white;
  box-shadow: 0 10px 24px rgba(15, 118, 110, 0.24);
}

.ghost-button {
  background: var(--surface);
  color: var(--accent-strong);
  border: 1px solid var(--line);
}

.icon-button {
  display: grid;
  place-items: center;
  width: 2.7rem;
  background: var(--surface);
  border: 1px solid var(--line);
}

.menu-toggle span {
  width: 1.2rem;
  height: 2px;
  margin: 2px 0;
  background: var(--ink);
}

.app-shell {
  display: grid;
  grid-template-columns: 16rem minmax(0, 1fr);
  gap: 1rem;
  max-width: 1440px;
  margin: 0 auto;
  padding: 1rem clamp(1rem, 4vw, 2rem) 4rem;
}

.side-nav {
  position: sticky;
  top: 5.5rem;
  align-self: start;
  display: grid;
  gap: 0.35rem;
  padding: 1rem;
  background: rgba(255, 255, 255, 0.82);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.side-nav a {
  padding: 0.72rem 0.8rem;
  border-radius: var(--radius);
  color: var(--muted);
  text-decoration: none;
  font-weight: 750;
}

.side-nav a:hover,
.side-nav a.active {
  background: var(--surface-strong);
  color: var(--accent-strong);
}

main {
  min-width: 0;
  max-width: 100%;
}

.hero {
  min-height: 76vh;
  display: grid;
  grid-template-columns: minmax(0, 1.05fr) minmax(18rem, 0.95fr);
  align-items: center;
  gap: clamp(1.2rem, 4vw, 3rem);
  padding: clamp(2rem, 5vw, 5rem) 0;
}

.hero h2 {
  max-width: 13ch;
  margin: 0;
  font-size: clamp(2.65rem, 7vw, 5.8rem);
  line-height: 0.94;
  letter-spacing: 0;
}

.hero p:not(.course-label) {
  max-width: 46rem;
  color: var(--muted);
  font-size: 1.08rem;
  line-height: 1.7;
}

.hero-figure,
.lesson-figure {
  margin: 0;
}

.hero-figure img,
.lesson-figure img {
  display: block;
  width: 100%;
  height: auto;
  border-radius: var(--radius);
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
}

.lesson-figure {
  margin-bottom: 1rem;
}

.progress-band,
.tool-panel,
.lesson-card,
.case-card,
.pathway article,
.timeline article {
  background: rgba(255, 255, 255, 0.9);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: 0 10px 30px rgba(15, 83, 78, 0.08);
}

.progress-band {
  display: grid;
  grid-template-columns: auto minmax(10rem, 1fr);
  gap: 1rem;
  align-items: center;
  padding: 1rem;
  margin-bottom: 2rem;
}

.progress-band strong {
  display: block;
  font-size: 1.6rem;
  color: var(--accent-strong);
}

.progress-band span {
  color: var(--muted);
}

.progress-track {
  height: 0.85rem;
  background: #d8ebe7;
  border-radius: 999px;
  overflow: hidden;
}

.progress-track span {
  display: block;
  width: 0;
  height: 100%;
  background: linear-gradient(90deg, var(--accent), var(--amber));
}

.lesson-section {
  padding: 3rem 0;
  scroll-margin-top: 5rem;
}

.section-heading {
  max-width: 48rem;
  margin-bottom: 1.25rem;
}

.section-heading h2 {
  margin: 0;
  font-size: clamp(2rem, 5vw, 3.4rem);
  line-height: 1;
}

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

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

.lesson-card,
.pathway article,
.timeline article,
.case-card {
  padding: 1.15rem;
}

.lesson-card h3,
.pathway h3,
.timeline h3,
.case-card h3 {
  margin-top: 0;
  font-size: 1.2rem;
}

.lesson-card p,
.lesson-card li,
.pathway p,
.timeline p,
.case-card li {
  color: var(--muted);
  line-height: 1.65;
}

.lesson-card ul,
.case-card ul,
.case-card ol {
  padding-left: 1.2rem;
}

.wide {
  margin-top: 1rem;
}

.compare-row {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.8rem;
  margin-top: 1rem;
}

.compare-row div {
  padding: 1rem;
  background: var(--surface-strong);
  border-radius: var(--radius);
}

.compare-row strong,
.compare-row span {
  display: block;
}

.compare-row span {
  margin-top: 0.35rem;
  color: var(--muted);
  line-height: 1.55;
}

.pathway,
.timeline,
.case-card {
  display: grid;
  gap: 1rem;
}

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

.timeline {
  grid-template-columns: repeat(5, minmax(0, 1fr));
}

.timeline span {
  display: grid;
  place-items: center;
  width: 2.3rem;
  height: 2.3rem;
  border-radius: 50%;
  background: var(--accent);
  color: white;
  font-weight: 900;
}

.case-card {
  grid-template-columns: repeat(2, minmax(0, 1fr));
  background: linear-gradient(145deg, #ffffff, #e8f7f4);
}

.tool-panel {
  display: grid;
  gap: 1rem;
  margin-top: 1rem;
  padding: 1rem;
}

.calculator {
  display: flex;
  flex-wrap: wrap;
  gap: 0.8rem;
  align-items: end;
}

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

.decision-form fieldset {
  display: grid;
  gap: 0.75rem;
  margin: 0;
  padding: 1rem;
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.decision-form legend {
  padding: 0 0.35rem;
  color: var(--accent-strong);
  font-weight: 900;
}

.decision-form button {
  width: fit-content;
}

.calculator label {
  display: grid;
  gap: 0.35rem;
  min-width: 9rem;
  color: var(--accent-strong);
  font-weight: 800;
}

.calculator input,
.calculator select,
.search-box input {
  width: 100%;
  min-height: 2.65rem;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 0.65rem 0.75rem;
  background: white;
  color: var(--ink);
}

.checkbox-label {
  grid-template-columns: auto 1fr;
  align-items: center;
}

.checkbox-label input {
  width: 1.15rem;
  min-height: 1.15rem;
}

.result-box {
  display: block;
  min-height: 3.5rem;
  padding: 1rem;
  border-radius: var(--radius);
  background: #ecfeff;
  color: #164e63;
  line-height: 1.55;
  font-weight: 750;
}

.quiz {
  display: grid;
  gap: 1rem;
}

.flashcards {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 1rem;
  margin-bottom: 1rem;
}

.flashcard {
  min-height: 13rem;
  border: 0;
  border-radius: var(--radius);
  padding: 1rem;
  background: var(--surface);
  box-shadow: 0 10px 30px rgba(15, 83, 78, 0.08);
  cursor: pointer;
  text-align: left;
  perspective: 1000px;
}

.flashcard-inner {
  min-height: 11rem;
  display: grid;
  align-content: center;
  gap: 0.8rem;
  padding: 1rem;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: linear-gradient(145deg, #ffffff, #e7f5f1);
}

.flashcard strong {
  color: var(--accent-strong);
  font-size: 1.05rem;
}

.flashcard span {
  color: var(--muted);
  line-height: 1.55;
}

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

.quiz-options {
  display: grid;
  gap: 0.6rem;
  margin-top: 0.75rem;
}

.quiz-options button {
  width: 100%;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #f8fafc;
  padding: 0.8rem;
  color: var(--ink);
  text-align: left;
  cursor: pointer;
}

.quiz-options button.correct {
  background: #dcfce7;
  border-color: #16a34a;
}

.quiz-options button.wrong {
  background: #ffe4e6;
  border-color: #e11d48;
}

.transcript-panel {
  position: fixed;
  inset: 0 0 0 auto;
  z-index: 40;
  width: min(48rem, 100vw);
  display: grid;
  grid-template-rows: auto auto 1fr;
  gap: 1rem;
  padding: 1rem;
  background: rgba(255, 255, 255, 0.98);
  border-left: 1px solid var(--line);
  box-shadow: -20px 0 60px rgba(15, 83, 78, 0.18);
  transform: translateX(105%);
  transition: transform 180ms ease;
}

.transcript-panel.open {
  transform: translateX(0);
}

.transcript-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.transcript-header h2 {
  margin: 0;
}

.close-transcript {
  font-size: 1.5rem;
}

.search-box {
  display: grid;
  gap: 0.4rem;
  color: var(--accent-strong);
  font-weight: 800;
}

.transcript-panel pre {
  margin: 0;
  padding: 1rem;
  overflow: auto;
  white-space: pre-wrap;
  line-height: 1.55;
  background: #f8fafc;
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.toast {
  position: fixed;
  right: 1rem;
  bottom: 1rem;
  z-index: 50;
  max-width: min(24rem, calc(100vw - 2rem));
  padding: 0.9rem 1rem;
  border-radius: var(--radius);
  background: var(--ink);
  color: white;
  box-shadow: var(--shadow);
  opacity: 0;
  transform: translateY(1rem);
  transition: opacity 160ms ease, transform 160ms ease;
}

.toast.show {
  opacity: 1;
  transform: translateY(0);
}

@media (max-width: 980px) {
  .app-shell,
  .hero,
  .content-grid,
  .content-grid.two,
  .pathway,
  .timeline,
  .case-card,
  .decision-form,
  .flashcards {
    grid-template-columns: 1fr;
  }

  .side-nav {
    position: fixed;
    inset: 4.6rem 1rem auto 1rem;
    z-index: 25;
    transform: translateY(-140%);
    transition: transform 180ms ease;
  }

  .side-nav.open {
    transform: translateY(0);
  }
}

@media (max-width: 680px) {
  .app-header {
    align-items: flex-start;
    justify-content: flex-start;
  }

  .header-actions {
    display: none;
  }

  .hero {
    min-height: auto;
    padding-top: 2rem;
  }

  .hero h2 {
    width: min(10.4ch, calc(100vw - 2rem));
    max-width: min(10.4ch, calc(100vw - 2rem));
    font-size: clamp(1.9rem, 9vw, 2.25rem);
    line-height: 1.02;
    overflow-wrap: anywhere;
  }

  .hero p:not(.course-label),
  .hero-copy,
  .hero-figure,
  .lesson-figure {
    width: min(100%, calc(100vw - 2rem));
    max-width: calc(100vw - 2rem);
    overflow-wrap: anywhere;
  }

  .hero p:not(.course-label) {
    max-width: 31ch;
  }

  .brand {
    max-width: calc(100vw - 6rem);
  }

  .brand h1 {
    font-size: 0.95rem;
    max-width: 11rem;
  }

  .progress-band,
  .compare-row {
    grid-template-columns: 1fr;
  }
}

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