:root {
  --bg: #f4efe6;
  --panel: rgba(255, 252, 247, 0.86);
  --panel-strong: #fffaf3;
  --ink: #1d1a17;
  --muted: #675f55;
  --line: rgba(63, 52, 39, 0.12);
  --accent: #22433b;
  --accent-soft: #d8e4de;
  --accent-warm: #b36a3c;
  --shadow: 0 18px 40px rgba(35, 29, 22, 0.08);
  --radius: 22px;
  --radius-sm: 16px;
  --content-width: 980px;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: "Iowan Old Style", "Palatino Linotype", "Book Antiqua", Georgia, serif;
  color: var(--ink);
  background:
    radial-gradient(circle at top left, rgba(255, 255, 255, 0.85), transparent 35%),
    linear-gradient(180deg, #f7f2ea 0%, #f1ebe0 100%);
  min-height: 100vh;
}

a {
  color: inherit;
  text-decoration: none;
}

code {
  font-family: "SFMono-Regular", "Menlo", monospace;
  font-size: 0.92em;
  background: rgba(34, 67, 59, 0.08);
  padding: 0.15rem 0.4rem;
  border-radius: 0.45rem;
}

.app-shell {
  display: grid;
  grid-template-columns: 320px minmax(0, 1fr);
  min-height: 100vh;
}

.sidebar {
  padding: 2rem 1.5rem;
  background: rgba(250, 245, 238, 0.94);
  border-right: 1px solid var(--line);
  position: sticky;
  top: 0;
  height: 100vh;
  overflow: auto;
}

.brand {
  padding: 1.2rem 1.2rem 1.4rem;
  background: linear-gradient(180deg, rgba(255, 250, 243, 0.98), rgba(241, 232, 220, 0.72));
  border: 1px solid rgba(63, 52, 39, 0.08);
  border-radius: 28px;
  box-shadow: var(--shadow);
}

.brand h1,
.breadcrumbs h2,
.chapter-hero h2,
.hero h2,
.section-heading h2 {
  font-family: "Baskerville", "Times New Roman", serif;
  letter-spacing: -0.02em;
}

.brand h1 {
  margin: 0.2rem 0 0.75rem;
  font-size: 2rem;
  line-height: 1.05;
}

.brand-copy {
  margin: 0;
  color: var(--muted);
  line-height: 1.55;
}

.sidebar-nav {
  display: grid;
  gap: 1.6rem;
  margin-top: 1.8rem;
}

.nav-group {
  display: grid;
  gap: 0.5rem;
}

.nav-label,
.mini-label,
.eyebrow,
.group-badge,
.concept-badge {
  font-family: "Avenir Next", "Helvetica Neue", Arial, sans-serif;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  font-size: 0.72rem;
  color: var(--muted);
}

.nav-link {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  padding: 0.72rem 0.9rem;
  border-radius: 14px;
  color: var(--ink);
  transition: background 140ms ease, transform 140ms ease;
}

.nav-link:hover,
.nav-link.is-active {
  background: rgba(34, 67, 59, 0.08);
  transform: translateX(2px);
}

.nav-tag {
  padding: 0.2rem 0.5rem;
  border-radius: 999px;
  font-size: 0.7rem;
  background: rgba(179, 106, 60, 0.12);
  color: var(--accent-warm);
}

.page-shell {
  min-width: 0;
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  justify-content: space-between;
  align-items: flex-end;
  gap: 1rem;
  padding: 1.6rem 2rem 1rem;
  backdrop-filter: blur(18px);
  background: rgba(244, 239, 230, 0.82);
  border-bottom: 1px solid rgba(63, 52, 39, 0.06);
}

.breadcrumbs h2 {
  margin: 0.2rem 0 0;
  font-size: 1.6rem;
}

.progress-pill {
  font-family: "Avenir Next", "Helvetica Neue", Arial, sans-serif;
  font-size: 0.88rem;
  padding: 0.65rem 0.95rem;
  border-radius: 999px;
  background: rgba(34, 67, 59, 0.08);
  color: var(--accent);
  white-space: nowrap;
}

.page-content {
  width: min(var(--content-width), calc(100% - 3rem));
  margin: 0 auto;
  padding: 2rem 0 4rem;
}

.note-card {
  background: var(--panel);
  border: 1px solid rgba(63, 52, 39, 0.08);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

.hero,
.chapter-hero {
  padding: 1.8rem 2rem;
}

.hero h2,
.chapter-hero h2 {
  margin: 0.35rem 0 0.9rem;
  font-size: clamp(2rem, 4vw, 3rem);
  line-height: 1.02;
}

.hero p,
.chapter-hero p,
.content-flow p,
.definition-card p,
.practice-item p,
.result-item p,
.stat-card p,
.home-card p {
  line-height: 1.7;
}

.hero-actions,
.chapter-hero-actions,
.card-actions,
.quick-links,
.quiz-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.8rem;
  margin-top: 1.2rem;
}

.button-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.85rem 1.1rem;
  border-radius: 999px;
  background: var(--accent);
  color: #f9f7f2;
  border: none;
  cursor: pointer;
  font-family: "Avenir Next", "Helvetica Neue", Arial, sans-serif;
  font-size: 0.92rem;
}

.button-link.subtle {
  background: rgba(34, 67, 59, 0.08);
  color: var(--accent);
}

.stats-grid,
.home-grid,
.definitions-grid {
  display: grid;
  gap: 1rem;
}

.stats-grid {
  grid-template-columns: repeat(3, minmax(0, 1fr));
  margin: 1.4rem 0 2rem;
}

.home-grid {
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
}

.definitions-grid {
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
}

.stat-card,
.home-card,
.definition-card {
  padding: 1.4rem;
}

.section-shell {
  margin-top: 2rem;
}

.section-heading {
  margin-bottom: 1rem;
}

.section-heading h2 {
  margin: 0.25rem 0 0;
  font-size: 1.9rem;
}

.chapter-overview {
  padding: 1.4rem 1.7rem;
  margin-top: 1.5rem;
}

.content-flow {
  display: grid;
  gap: 1.2rem;
}

.topic-group {
  display: grid;
  gap: 1rem;
}

.group-heading {
  padding: 0.4rem 0.2rem 0.1rem;
}

.group-heading h2 {
  margin: 0.15rem 0 0;
  font-size: 1.55rem;
}

.concept-card {
  padding: 1.4rem 1.6rem;
}

.concept-layout {
  display: grid;
  gap: 0.9rem;
}

.concept-header {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-bottom: 1rem;
}

.concept-header h3 {
  margin: 0;
  font-size: 1.5rem;
}

.concept-badge {
  display: inline-flex;
  align-items: center;
  padding: 0.42rem 0.6rem;
  background: rgba(179, 106, 60, 0.1);
  color: var(--accent-warm);
  border-radius: 999px;
}

.detail-block {
  padding: 1rem 1.05rem;
  border-radius: 18px;
  background: rgba(255, 255, 255, 0.52);
  border: 1px solid rgba(63, 52, 39, 0.06);
}

.detail-block + .detail-block {
  margin-top: 0.1rem;
}

.detail-block h4 {
  margin: 0.15rem 0 0.75rem;
  font-size: 1.02rem;
  font-family: "Avenir Next", "Helvetica Neue", Arial, sans-serif;
}

.detail-label {
  margin: 0;
  font-family: "Avenir Next", "Helvetica Neue", Arial, sans-serif;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  font-size: 0.72rem;
  color: var(--muted);
}

.detail-content > :first-child {
  margin-top: 0.3rem;
}

.detail-definition {
  background: rgba(34, 67, 59, 0.08);
}

.detail-why {
  background: rgba(179, 106, 60, 0.09);
}

.detail-framework {
  background: rgba(216, 228, 222, 0.42);
}

.nested-detail {
  margin-top: 0.85rem;
}

.content-flow ul,
.content-flow ol,
.chapter-overview ul,
.chapter-overview ol {
  margin: 0.7rem 0 0.8rem 1.2rem;
  padding: 0;
}

.content-flow li,
.chapter-overview li {
  margin: 0.4rem 0;
  padding-left: 0.2rem;
  line-height: 1.6;
}

.subtopic-block {
  margin-top: 1rem;
  padding-top: 1rem;
  border-top: 1px solid rgba(63, 52, 39, 0.07);
}

.subtopic-block h4,
.subtopic-block h5 {
  margin: 0 0 0.7rem;
  font-size: 1.08rem;
  font-family: "Avenir Next", "Helvetica Neue", Arial, sans-serif;
}

.question-list {
  display: grid;
  gap: 0.95rem;
  padding: 1rem;
}

.practice-shell {
  padding: 1rem 1.2rem;
}

.practice-list {
  margin: 0;
  padding-left: 1.35rem;
  display: grid;
  gap: 0.8rem;
}

.practice-item {
  padding: 0.2rem 0 0.2rem 0.2rem;
}

.practice-copy {
  padding-left: 0.35rem;
  border-left: 2px solid rgba(34, 67, 59, 0.14);
}

.flashcard-controls {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem 1.2rem;
  margin-bottom: 1rem;
}

.flashcard-status {
  display: grid;
  justify-items: center;
  gap: 0.35rem;
}

.flashcard-kind {
  display: inline-flex;
  align-items: center;
  padding: 0.25rem 0.65rem;
  border-radius: 999px;
  background: rgba(45, 72, 64, 0.08);
  color: var(--muted);
  font-family: "Avenir Next", "Helvetica Neue", Arial, sans-serif;
  font-size: 0.78rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.flashcard {
  width: 100%;
  text-align: left;
  padding: 2rem;
  background: linear-gradient(180deg, rgba(255, 253, 249, 0.96), rgba(243, 237, 228, 0.9));
  border: 1px solid rgba(63, 52, 39, 0.08);
  cursor: pointer;
  min-height: 340px;
  transition: transform 180ms ease, box-shadow 180ms ease;
}

.flashcard-compact {
  min-height: 280px;
}

.flashcard:hover {
  transform: translateY(-2px);
}

.flashcard-label,
.flashcard-hint {
  font-family: "Avenir Next", "Helvetica Neue", Arial, sans-serif;
  color: var(--muted);
}

.flashcard-label {
  letter-spacing: 0.08em;
  text-transform: uppercase;
  font-size: 0.78rem;
}

.flashcard h3 {
  margin: 0.8rem 0 0;
  font-size: clamp(1.5rem, 3vw, 2.4rem);
  line-height: 1.15;
}

.flashcard-back {
  margin-top: 1.2rem;
  font-size: 1.05rem;
  line-height: 1.8;
  color: var(--muted);
  max-width: 62ch;
}

.flashcard.is-flipped {
  background: linear-gradient(180deg, rgba(34, 67, 59, 0.96), rgba(22, 42, 37, 0.96));
  color: #f7f3eb;
}

.flashcard.is-flipped .flashcard-back,
.flashcard.is-flipped .flashcard-label,
.flashcard.is-flipped .flashcard-hint,
.flashcard.is-flipped .flashcard-kind {
  color: rgba(247, 243, 235, 0.82);
}

.flashcard.is-flipped .flashcard-kind {
  background: rgba(247, 243, 235, 0.12);
}

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

.quiz-card {
  padding: 1.3rem 1.4rem;
}

.quiz-card h3 {
  margin: 0.35rem 0 1rem;
  font-size: 1.2rem;
}

.quiz-options {
  display: grid;
  gap: 0.65rem;
}

.quiz-option {
  display: flex;
  gap: 0.75rem;
  align-items: flex-start;
  padding: 0.8rem 0.9rem;
  border-radius: 14px;
  background: rgba(255, 255, 255, 0.55);
}

.results-card,
.weak-group {
  padding: 1.4rem;
  margin-top: 1rem;
}

.chapter-hero-actions {
  margin-top: 1.1rem;
}

.results-list {
  display: grid;
  gap: 0.75rem;
  margin-top: 1rem;
}

.result-item {
  padding: 0.9rem 1rem;
  border-radius: 16px;
  background: rgba(255, 255, 255, 0.5);
}

@media (max-width: 980px) {
  .app-shell {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: static;
    height: auto;
    border-right: none;
    border-bottom: 1px solid var(--line);
  }

  .topbar {
    padding-inline: 1rem;
  }

  .page-content {
    width: min(var(--content-width), calc(100% - 2rem));
  }

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