:root {
  --bg: #f7f1e8;
  --paper: #fffaf2;
  --ink: #1f1b16;
  --muted: #6e6254;
  --line: rgba(58, 44, 28, 0.14);
  --accent: #8a4b2a;
  --accent-strong: #62331b;
  --success: #2e6a44;
  --font-display: "Iowan Old Style", "Palatino Linotype", "Book Antiqua", serif;
  --font-body: "Georgia", "Times New Roman", serif;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100vh;
  color: var(--ink);
  font-family: var(--font-body);
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.35), transparent 220px),
    linear-gradient(135deg, #f8f3eb 0%, #f3ebdf 48%, #efe6d8 100%);
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  background:
    radial-gradient(circle at top right, rgba(138, 75, 42, 0.08), transparent 24%),
    radial-gradient(circle at bottom left, rgba(98, 51, 27, 0.05), transparent 22%);
}

#app {
  width: min(760px, calc(100% - 32px));
  margin: 0 auto;
  padding: 40px 0 72px;
  position: relative;
}

.app-shell {
  display: block;
}

.hero,
.panel,
.quiz-card {
  background: transparent;
  border: 0;
  box-shadow: none;
  padding: 0;
}

.hero {
  margin-bottom: 28px;
}

.hero-top,
.hero-actions,
.panel-header,
.result-summary,
.quiz-toolbar {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
}

.eyebrow,
.mini-label,
.stat-label,
.concept-tag,
.status-strip span,
.progress-meta,
.score-pill,
.difficulty-pill {
  color: var(--muted);
  font-size: 0.92rem;
}

.eyebrow {
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.hero h1 {
  margin: 10px 0 14px;
  font-family: var(--font-display);
  font-size: clamp(2.7rem, 8vw, 4.8rem);
  font-weight: 600;
  line-height: 0.96;
  letter-spacing: -0.03em;
  text-wrap: balance;
}

.hero p,
.panel p,
.quiz-card p,
.concept-card p,
.result-card p,
.subsection p,
.body-copy li {
  font-size: 1.08rem;
  line-height: 1.85;
}

.hero-actions {
  margin: 20px 0 10px;
}

.button-row,
.tabs,
.pill-row {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

.btn,
.tab,
.toggle-button,
.ghost-button,
.option-button {
  appearance: none;
  border: 0;
  background: transparent;
  color: var(--accent);
  font: inherit;
  cursor: pointer;
  padding: 0;
  transition: color 160ms ease;
}

.btn:hover,
.tab:hover,
.toggle-button:hover,
.ghost-button:hover,
.option-button:hover {
  color: var(--accent-strong);
}

.btn-primary,
.btn-secondary,
.btn-soft,
.tab,
.toggle-button,
.ghost-button,
.option-button {
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 0.2em;
}

.tab.active {
  color: var(--ink);
  text-decoration-color: var(--ink);
}

.stats-grid {
  display: flex;
  gap: 24px;
  flex-wrap: wrap;
  margin: 20px 0 8px;
}

.stat-card {
  min-width: 120px;
}

.stat-value {
  display: block;
  margin-top: 4px;
  font-family: var(--font-display);
  font-size: 1.4rem;
  color: var(--accent-strong);
}

.status-strip {
  margin-top: 14px;
  padding-top: 14px;
  border-top: 1px solid var(--line);
}

.status-strip strong {
  display: block;
  margin-bottom: 4px;
  font-size: 1rem;
  font-weight: 600;
}

.surface-stack {
  display: grid;
  gap: 28px;
}

.panel,
.quiz-card {
  padding-top: 20px;
  border-top: 1px solid var(--line);
}

.panel h2,
.quiz-card h2 {
  margin: 0 0 12px;
  font-family: var(--font-display);
  font-size: clamp(1.6rem, 4vw, 2rem);
  font-weight: 600;
  letter-spacing: -0.02em;
}

.section-grid,
.concept-grid,
.results-grid {
  display: grid;
  gap: 22px;
}

.section-card,
.concept-card,
.result-card,
.subsection {
  padding: 0;
  border: 0;
  background: transparent;
}

.subsection {
  transition: background 160ms ease, border-color 160ms ease, padding 160ms ease;
}

.section-card {
  padding-bottom: 22px;
  border-bottom: 1px solid rgba(58, 44, 28, 0.08);
}

.section-card.completed h3,
.subsection.completed h3 {
  color: var(--success);
}

.subsection.completed {
  background: linear-gradient(180deg, rgba(46, 106, 68, 0.08), rgba(46, 106, 68, 0.03));
  border-left: 4px solid rgba(46, 106, 68, 0.72);
  border-radius: 6px;
}

.subsection.completed .toggle-button {
  color: var(--success);
  text-decoration-color: rgba(46, 106, 68, 0.72);
}

.section-card h3,
.concept-card h3,
.result-card h3,
.subsection h3,
.subsection h4 {
  margin: 0 0 10px;
  font-family: var(--font-display);
  font-weight: 600;
  letter-spacing: -0.02em;
}

.section-card h3,
.subsection h3 {
  font-size: 1.45rem;
}

.subsection h4 {
  margin-top: 20px;
  font-size: 1.15rem;
}

.body-copy {
  display: grid;
  gap: 22px;
}

.body-copy ul,
.subsection ul {
  margin: 6px 0 0;
  padding-left: 24px;
}

.progress-shell {
  margin: 18px 0 20px;
}

.progress-meta {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 8px;
}

.progress-bar {
  width: 100%;
  height: 4px;
  background: rgba(58, 44, 28, 0.08);
}

.progress-bar span {
  display: block;
  height: 100%;
  background: var(--accent);
}

.option-list {
  display: grid;
  gap: 12px;
  margin-top: 16px;
}

.option-button {
  color: var(--ink);
  text-align: left;
  line-height: 1.65;
}

.option-button::before {
  content: "→ ";
  color: var(--accent);
}

.result-summary {
  margin-bottom: 18px;
}

.score-pill,
.difficulty-pill {
  padding: 0;
}

.empty-state {
  color: var(--muted);
}

@media (max-width: 720px) {
  #app {
    width: min(100% - 24px, 760px);
    padding: 24px 0 48px;
  }

  .hero h1 {
    font-size: clamp(2.3rem, 12vw, 3.6rem);
  }

  .hero p,
  .panel p,
  .quiz-card p,
  .concept-card p,
  .result-card p,
  .subsection p,
  .body-copy li {
    font-size: 1rem;
    line-height: 1.78;
  }

  .stats-grid {
    gap: 16px;
  }

  .hero-top,
  .hero-actions,
  .panel-header,
  .result-summary,
  .quiz-toolbar,
  .progress-meta {
    display: block;
  }

  .tabs,
  .button-row,
  .pill-row {
    margin-top: 8px;
  }
}