/* ============================================
   ANTIFRAGILE — Shared Design System
   Extracted from zh.html for cross-page reuse
   ============================================ */

/* CUSTOM PROPERTIES */
:root {
  --bg-deep: #0a0a08;
  --bg-surface: #121210;
  --bg-elevated: #1a1a16;
  --bg-card: #1e1e19;
  --text-primary: #e8e4d9;
  --text-secondary: #9e9a8f;
  --text-muted: #6b6860;
  --fragile-color: #c94040;
  --fragile-glow: #c9404033;
  --robust-color: #7a7a72;
  --robust-glow: #7a7a7233;
  --antifragile-color: #c9a84c;
  --antifragile-glow: #c9a84c33;
  --accent: #c9a84c;
  --accent-dim: #c9a84c22;
  --border: #2a2a24;
  --border-light: #3a3a32;
  --success: #5a9e6f;
  --error: #c94040;
  --font-display: 'Playfair Display', Georgia, serif;
  --font-body: 'Noto Serif SC', 'Source Serif 4', Georgia, serif;
  --font-mono: 'JetBrains Mono', monospace;
  --ease-out-expo: cubic-bezier(0.16, 1, 0.3, 1);
  --ease-spring: cubic-bezier(0.34, 1.56, 0.64, 1);
}

/* RESET */
* { margin: 0; padding: 0; box-sizing: border-box; }

html {
  scroll-behavior: smooth;
  scrollbar-width: thin;
  scrollbar-color: var(--border-light) var(--bg-deep);
}

body {
  background: var(--bg-deep);
  color: var(--text-primary);
  font-family: var(--font-body);
  font-size: 17px;
  line-height: 1.7;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

::selection {
  background: var(--accent);
  color: var(--bg-deep);
}

/* NOISE TEXTURE OVERLAY */
body::before {
  content: '';
  position: fixed;
  inset: 0;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 256 256' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='noise'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='4' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23noise)' opacity='0.03'/%3E%3C/svg%3E");
  pointer-events: none;
  z-index: 9999;
}

/* NAVIGATION */
nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: rgba(10, 10, 8, 0.85);
  backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border);
  transition: transform 0.4s var(--ease-out-expo);
}

nav.hidden { transform: translateY(-100%); }

.nav-inner {
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 40px;
  height: 60px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav-logo {
  font-family: var(--font-display);
  font-size: 18px;
  font-weight: 700;
  letter-spacing: 0.05em;
  color: var(--text-primary);
  cursor: pointer;
}

.nav-logo span { color: var(--accent); }

.nav-tabs {
  display: flex;
  gap: 4px;
}

.nav-tab {
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  padding: 8px 16px;
  border: 1px solid transparent;
  border-radius: 4px;
  background: none;
  color: var(--text-muted);
  cursor: pointer;
  transition: all 0.3s ease;
}

.nav-tab:hover { color: var(--text-secondary); border-color: var(--border); }
.nav-tab.active { color: var(--accent); border-color: var(--accent); background: var(--accent-dim); }

.progress-bar {
  position: absolute;
  bottom: 0;
  left: 0;
  height: 2px;
  background: linear-gradient(90deg, var(--accent), var(--antifragile-color));
  transition: width 0.3s ease;
}

/* HERO SECTION */
.hero {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  text-align: center;
  padding: 120px 40px 80px;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: -200px;
  left: 50%;
  transform: translateX(-50%);
  width: 800px;
  height: 800px;
  background: radial-gradient(circle, var(--antifragile-glow) 0%, transparent 70%);
  pointer-events: none;
}

.hero-subtitle {
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.3em;
  color: var(--accent);
  margin-bottom: 32px;
  opacity: 0;
  animation: fadeUp 0.8s var(--ease-out-expo) 0.2s forwards;
}

.hero-title {
  font-family: var(--font-display);
  font-size: clamp(56px, 8vw, 120px);
  font-weight: 900;
  line-height: 0.95;
  letter-spacing: -0.02em;
  margin-bottom: 24px;
  opacity: 0;
  animation: fadeUp 0.8s var(--ease-out-expo) 0.4s forwards;
}

.hero-title em {
  font-style: italic;
  color: var(--accent);
}

.hero-desc {
  max-width: 600px;
  font-size: 19px;
  color: var(--text-secondary);
  line-height: 1.7;
  margin-bottom: 48px;
  opacity: 0;
  animation: fadeUp 0.8s var(--ease-out-expo) 0.6s forwards;
}

.hero-triad {
  display: flex;
  gap: 48px;
  opacity: 0;
  animation: fadeUp 0.8s var(--ease-out-expo) 0.8s forwards;
}

.triad-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
}

.triad-icon {
  width: 48px;
  height: 48px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 22px;
  margin-bottom: 4px;
  transition: transform 0.3s var(--ease-spring);
}

.triad-icon:hover { transform: scale(1.15); }

.triad-icon.fragile { background: var(--fragile-glow); border: 1px solid var(--fragile-color); }
.triad-icon.robust { background: var(--robust-glow); border: 1px solid var(--robust-color); }
.triad-icon.antifragile { background: var(--antifragile-glow); border: 1px solid var(--antifragile-color); }

.triad-label {
  font-family: var(--font-mono);
  font-size: 10px;
  text-transform: uppercase;
  letter-spacing: 0.15em;
}

.triad-label.fragile { color: var(--fragile-color); }
.triad-label.robust { color: var(--robust-color); }
.triad-label.antifragile { color: var(--antifragile-color); }

.scroll-hint {
  position: absolute;
  bottom: 40px;
  left: 50%;
  transform: translateX(-50%);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  opacity: 0;
  animation: fadeUp 0.8s var(--ease-out-expo) 1.2s forwards;
}

.scroll-hint span {
  font-family: var(--font-mono);
  font-size: 10px;
  text-transform: uppercase;
  letter-spacing: 0.2em;
  color: var(--text-muted);
}

.scroll-line {
  width: 1px;
  height: 40px;
  background: var(--border-light);
  position: relative;
  overflow: hidden;
}

.scroll-line::after {
  content: '';
  position: absolute;
  top: -40px;
  left: 0;
  width: 1px;
  height: 40px;
  background: var(--accent);
  animation: scrollPulse 2s ease infinite;
}

/* SECTIONS */
.section {
  display: none;
  padding: 100px 40px 80px;
  max-width: 1400px;
  margin: 0 auto;
  min-height: 100vh;
}

.section.active { display: block; }

.section-header {
  margin-bottom: 64px;
  padding-bottom: 32px;
  border-bottom: 1px solid var(--border);
}

.section-label {
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.2em;
  color: var(--accent);
  margin-bottom: 16px;
}

.section-title {
  font-family: var(--font-display);
  font-size: 42px;
  font-weight: 700;
  line-height: 1.15;
  margin-bottom: 16px;
}

.section-desc {
  font-size: 18px;
  color: var(--text-secondary);
  max-width: 640px;
}

/* BOOK MAP */
.book-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(380px, 1fr));
  gap: 24px;
}

.book-card {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 32px;
  cursor: pointer;
  transition: all 0.4s var(--ease-out-expo);
  position: relative;
  overflow: hidden;
}

.book-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--accent), transparent);
  opacity: 0;
  transition: opacity 0.3s ease;
}

.book-card:hover {
  border-color: var(--border-light);
  transform: translateY(-2px);
  box-shadow: 0 8px 32px rgba(0,0,0,0.3);
}

.book-card:hover::before { opacity: 1; }

.book-card-num {
  font-family: var(--font-display);
  font-size: 48px;
  font-weight: 900;
  color: var(--bg-elevated);
  position: absolute;
  top: 16px;
  right: 24px;
  line-height: 1;
  transition: color 0.3s ease;
}

.book-card:hover .book-card-num { color: var(--accent-dim); }

.book-card-label {
  font-family: var(--font-mono);
  font-size: 10px;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--accent);
  margin-bottom: 12px;
}

.book-card-title {
  font-family: var(--font-display);
  font-size: 22px;
  font-weight: 700;
  line-height: 1.3;
  margin-bottom: 16px;
  padding-right: 40px;
}

.book-card-desc {
  font-size: 15px;
  color: var(--text-secondary);
  line-height: 1.65;
  margin-bottom: 20px;
}

.book-card-chapters {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.chapter-tag {
  font-family: var(--font-mono);
  font-size: 10px;
  padding: 4px 10px;
  border: 1px solid var(--border);
  border-radius: 3px;
  color: var(--text-muted);
  transition: all 0.2s ease;
}

.book-card:hover .chapter-tag { border-color: var(--border-light); color: var(--text-secondary); }

/* EXPANDED CHAPTER VIEW */
.chapter-detail {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  margin-bottom: 20px;
  overflow: hidden;
  transition: all 0.3s ease;
}

.chapter-detail-header {
  padding: 24px 32px;
  cursor: pointer;
  display: flex;
  align-items: flex-start;
  gap: 16px;
  transition: background 0.2s ease;
}

.chapter-detail-header:hover { background: var(--bg-elevated); }

.chapter-num {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--accent);
  min-width: 32px;
}

.chapter-detail-title {
  font-family: var(--font-display);
  font-size: 20px;
  font-weight: 700;
  flex: 1;
}

.chapter-toggle {
  font-size: 18px;
  color: var(--text-muted);
  transition: transform 0.3s ease;
}

.chapter-detail.open .chapter-toggle { transform: rotate(45deg); }

.chapter-detail-body {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.5s var(--ease-out-expo);
}

.chapter-detail.open .chapter-detail-body { max-height: 2000px; }

.chapter-detail-content {
  padding: 0 32px 32px;
  padding-left: 72px;
}

.chapter-detail-content p {
  color: var(--text-secondary);
  margin-bottom: 16px;
  font-size: 16px;
}

.chapter-detail-content .key-ideas {
  margin-top: 20px;
}

.chapter-detail-content .key-ideas h4 {
  font-family: var(--font-mono);
  font-size: 10px;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--accent);
  margin-bottom: 12px;
}

.idea-chip {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 12px;
  padding: 6px 14px;
  margin: 0 6px 8px 0;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 4px;
  color: var(--text-secondary);
}

/* CONCEPTS SECTION */
.concepts-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(340px, 1fr));
  gap: 20px;
}

.concept-card {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 28px;
  cursor: pointer;
  transition: all 0.4s var(--ease-out-expo);
  position: relative;
}

.concept-card:hover {
  border-color: var(--accent);
  transform: translateY(-2px);
  box-shadow: 0 4px 24px rgba(201, 168, 76, 0.08);
}

.concept-card .triad-badge {
  font-family: var(--font-mono);
  font-size: 9px;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  padding: 3px 10px;
  border-radius: 3px;
  display: inline-block;
  margin-bottom: 16px;
}

.triad-badge.fragile { background: var(--fragile-glow); color: var(--fragile-color); border: 1px solid var(--fragile-color); }
.triad-badge.robust { background: var(--robust-glow); color: var(--robust-color); border: 1px solid var(--robust-color); }
.triad-badge.antifragile { background: var(--antifragile-glow); color: var(--antifragile-color); border: 1px solid var(--antifragile-color); }
.triad-badge.meta { background: var(--accent-dim); color: var(--accent); border: 1px solid var(--accent); }

.concept-card h3 {
  font-family: var(--font-display);
  font-size: 22px;
  font-weight: 700;
  margin-bottom: 12px;
}

.concept-card p {
  font-size: 15px;
  color: var(--text-secondary);
  line-height: 1.65;
}

.concept-card .concept-example {
  margin-top: 16px;
  padding-top: 16px;
  border-top: 1px solid var(--border);
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--text-muted);
  line-height: 1.6;
}

.concept-card .concept-example em {
  color: var(--accent);
  font-style: normal;
}

/* CONCEPT DETAIL MODAL */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(10, 10, 8, 0.9);
  backdrop-filter: blur(8px);
  z-index: 2000;
  display: none;
  align-items: center;
  justify-content: center;
  padding: 40px;
  animation: fadeIn 0.3s ease;
}

.modal-overlay.open { display: flex; }

.modal {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  max-width: 720px;
  width: 100%;
  max-height: 85vh;
  overflow-y: auto;
  padding: 48px;
  position: relative;
  animation: modalIn 0.4s var(--ease-out-expo);
}

.modal-close {
  position: absolute;
  top: 20px;
  right: 20px;
  width: 36px;
  height: 36px;
  border: 1px solid var(--border);
  border-radius: 50%;
  background: none;
  color: var(--text-muted);
  font-size: 18px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s ease;
}

.modal-close:hover { border-color: var(--text-secondary); color: var(--text-primary); }

.modal h2 {
  font-family: var(--font-display);
  font-size: 32px;
  font-weight: 700;
  margin-bottom: 8px;
}

.modal .modal-subtitle {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  margin-bottom: 24px;
}

.modal p {
  color: var(--text-secondary);
  margin-bottom: 16px;
  font-size: 16px;
}

.modal blockquote {
  border-left: 2px solid var(--accent);
  padding: 16px 24px;
  margin: 24px 0;
  background: var(--bg-elevated);
  border-radius: 0 6px 6px 0;
  font-style: italic;
  color: var(--text-primary);
}

.modal .related-concepts {
  margin-top: 32px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
}

.modal .related-concepts h4 {
  font-family: var(--font-mono);
  font-size: 10px;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--text-muted);
  margin-bottom: 12px;
}

.related-tag {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 12px;
  padding: 6px 14px;
  margin: 0 6px 8px 0;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 4px;
  color: var(--accent);
  cursor: pointer;
  transition: all 0.2s ease;
}

.related-tag:hover { border-color: var(--accent); background: var(--accent-dim); }

/* TRIAD CLASSIFIER */
.classifier-container {
  max-width: 800px;
  margin: 0 auto;
}

.classifier-prompt {
  text-align: center;
  margin-bottom: 48px;
}

.classifier-prompt h3 {
  font-family: var(--font-display);
  font-size: 28px;
  margin-bottom: 8px;
}

.classifier-prompt p {
  color: var(--text-secondary);
}

.classifier-scenario {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 40px;
  margin-bottom: 32px;
  text-align: center;
}

.scenario-num {
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.15em;
  margin-bottom: 16px;
}

.scenario-text {
  font-family: var(--font-display);
  font-size: 26px;
  font-weight: 700;
  line-height: 1.35;
  margin-bottom: 8px;
}

.scenario-context {
  color: var(--text-secondary);
  font-size: 15px;
}

.classifier-options {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
  margin-bottom: 32px;
}

.classify-btn {
  padding: 20px;
  border-radius: 8px;
  border: 2px solid var(--border);
  background: var(--bg-surface);
  cursor: pointer;
  transition: all 0.3s var(--ease-spring);
  text-align: center;
}

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

.classify-btn.fragile:hover, .classify-btn.fragile.selected { border-color: var(--fragile-color); background: var(--fragile-glow); }
.classify-btn.robust:hover, .classify-btn.robust.selected { border-color: var(--robust-color); background: var(--robust-glow); }
.classify-btn.antifragile:hover, .classify-btn.antifragile.selected { border-color: var(--antifragile-color); background: var(--antifragile-glow); }

.classify-btn .btn-icon { font-size: 28px; margin-bottom: 8px; }

.classify-btn .btn-label {
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.1em;
}

.classify-btn.fragile .btn-label { color: var(--fragile-color); }
.classify-btn.robust .btn-label { color: var(--robust-color); }
.classify-btn.antifragile .btn-label { color: var(--antifragile-color); }

.classify-btn .btn-desc {
  font-size: 12px;
  color: var(--text-muted);
  margin-top: 4px;
}

.feedback-box {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 28px;
  display: none;
  animation: fadeUp 0.3s var(--ease-out-expo);
}

.feedback-box.visible { display: block; }

.feedback-box.correct { border-color: var(--success); }
.feedback-box.incorrect { border-color: var(--error); }

.feedback-result {
  font-family: var(--font-mono);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  margin-bottom: 8px;
}

.feedback-result.correct { color: var(--success); }
.feedback-result.incorrect { color: var(--error); }

.feedback-box p {
  color: var(--text-secondary);
  font-size: 15px;
}

.classifier-controls {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 24px;
}

.classifier-score {
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--text-muted);
}

.classifier-score span { color: var(--accent); font-weight: 500; }

.next-btn {
  font-family: var(--font-mono);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  padding: 12px 24px;
  border: 1px solid var(--accent);
  border-radius: 4px;
  background: none;
  color: var(--accent);
  cursor: pointer;
  transition: all 0.2s ease;
}

.next-btn:hover { background: var(--accent); color: var(--bg-deep); }

/* FLASHCARDS */
.flashcard-container {
  max-width: 680px;
  margin: 0 auto;
}

.flashcard-controls {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 32px;
}

.flashcard-counter {
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--text-muted);
}

.flashcard-counter span { color: var(--accent); }

.flashcard-filter {
  display: flex;
  gap: 8px;
}

.filter-btn {
  font-family: var(--font-mono);
  font-size: 10px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  padding: 6px 14px;
  border: 1px solid var(--border);
  border-radius: 4px;
  background: none;
  color: var(--text-muted);
  cursor: pointer;
  transition: all 0.2s ease;
}

.filter-btn:hover { border-color: var(--text-secondary); color: var(--text-secondary); }
.filter-btn.active { border-color: var(--accent); color: var(--accent); background: var(--accent-dim); }

.flashcard-wrapper {
  perspective: 1200px;
  margin-bottom: 32px;
}

.flashcard {
  width: 100%;
  min-height: 360px;
  position: relative;
  cursor: pointer;
  transform-style: preserve-3d;
  transition: transform 0.6s var(--ease-out-expo);
}

.flashcard.flipped { transform: rotateY(180deg); }

.flashcard-face {
  position: absolute;
  inset: 0;
  backface-visibility: hidden;
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 48px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  text-align: center;
}

.flashcard-front {
  background: var(--bg-surface);
}

.flashcard-back {
  background: var(--bg-elevated);
  transform: rotateY(180deg);
}

.flashcard-category {
  font-family: var(--font-mono);
  font-size: 10px;
  text-transform: uppercase;
  letter-spacing: 0.2em;
  color: var(--accent);
  margin-bottom: 24px;
}

.flashcard-question {
  font-family: var(--font-display);
  font-size: 26px;
  font-weight: 700;
  line-height: 1.35;
  margin-bottom: 24px;
}

.flashcard-hint {
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--text-muted);
}

.flashcard-answer {
  font-size: 17px;
  color: var(--text-secondary);
  line-height: 1.7;
  max-width: 520px;
}

.flashcard-answer strong {
  color: var(--text-primary);
}

.flashcard-nav {
  display: flex;
  justify-content: center;
  gap: 16px;
}

.card-nav-btn {
  width: 48px;
  height: 48px;
  border: 1px solid var(--border);
  border-radius: 50%;
  background: none;
  color: var(--text-secondary);
  font-size: 20px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s ease;
}

.card-nav-btn:hover { border-color: var(--accent); color: var(--accent); }

.difficulty-btns {
  display: flex;
  gap: 12px;
  margin: 0 16px;
}

.diff-btn {
  font-family: var(--font-mono);
  font-size: 10px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  padding: 12px 20px;
  border: 1px solid var(--border);
  border-radius: 4px;
  background: none;
  color: var(--text-muted);
  cursor: pointer;
  transition: all 0.2s ease;
}

.diff-btn:hover { border-color: var(--text-secondary); color: var(--text-secondary); }
.diff-btn.easy:hover { border-color: var(--success); color: var(--success); }
.diff-btn.hard:hover { border-color: var(--error); color: var(--error); }
.diff-btn.good:hover { border-color: var(--accent); color: var(--accent); }

/* QUIZ */
.quiz-container {
  max-width: 740px;
  margin: 0 auto;
}

.quiz-progress {
  display: flex;
  gap: 4px;
  margin-bottom: 40px;
}

.quiz-dot {
  flex: 1;
  height: 4px;
  border-radius: 2px;
  background: var(--border);
  transition: background 0.3s ease;
}

.quiz-dot.correct { background: var(--success); }
.quiz-dot.incorrect { background: var(--error); }
.quiz-dot.current { background: var(--accent); }

.quiz-question-card {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 48px;
  margin-bottom: 24px;
}

.quiz-q-num {
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.15em;
  margin-bottom: 16px;
}

.quiz-q-text {
  font-family: var(--font-display);
  font-size: 24px;
  font-weight: 700;
  line-height: 1.4;
  margin-bottom: 32px;
}

.quiz-options {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.quiz-option {
  padding: 18px 24px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--bg-elevated);
  cursor: pointer;
  font-size: 16px;
  color: var(--text-secondary);
  transition: all 0.2s ease;
  display: flex;
  align-items: center;
  gap: 16px;
}

.quiz-option:hover { border-color: var(--accent); color: var(--text-primary); }

.quiz-option .option-letter {
  font-family: var(--font-mono);
  font-size: 12px;
  width: 28px;
  height: 28px;
  border: 1px solid var(--border);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  transition: all 0.2s ease;
}

.quiz-option:hover .option-letter { border-color: var(--accent); color: var(--accent); }

.quiz-option.selected { border-color: var(--accent); background: var(--accent-dim); }
.quiz-option.correct { border-color: var(--success); background: rgba(90, 158, 111, 0.1); }
.quiz-option.incorrect { border-color: var(--error); background: rgba(201, 64, 64, 0.1); }
.quiz-option.disabled { pointer-events: none; }

.quiz-explanation {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 24px;
  margin-top: 16px;
  display: none;
}

.quiz-explanation.visible { display: block; animation: fadeUp 0.3s var(--ease-out-expo); }

.quiz-explanation p {
  color: var(--text-secondary);
  font-size: 15px;
}

.quiz-results {
  text-align: center;
  padding: 60px 40px;
}

.quiz-results h3 {
  font-family: var(--font-display);
  font-size: 36px;
  margin-bottom: 16px;
}

.quiz-score {
  font-family: var(--font-display);
  font-size: 72px;
  font-weight: 900;
  color: var(--accent);
  margin-bottom: 16px;
}

.quiz-results p {
  color: var(--text-secondary);
  margin-bottom: 32px;
}

.restart-btn {
  font-family: var(--font-mono);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  padding: 14px 32px;
  border: 1px solid var(--accent);
  border-radius: 4px;
  background: var(--accent);
  color: var(--bg-deep);
  cursor: pointer;
  transition: all 0.2s ease;
}

.restart-btn:hover { background: transparent; color: var(--accent); }

/* PROGRESS SECTION */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
  margin-bottom: 48px;
}

.stat-card {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 28px;
  text-align: center;
}

.stat-value {
  font-family: var(--font-display);
  font-size: 42px;
  font-weight: 900;
  color: var(--accent);
  margin-bottom: 4px;
}

.stat-label {
  font-family: var(--font-mono);
  font-size: 10px;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--text-muted);
}

.mastery-section {
  margin-bottom: 48px;
}

.mastery-section h3 {
  font-family: var(--font-display);
  font-size: 24px;
  margin-bottom: 24px;
}

.mastery-item {
  display: flex;
  align-items: center;
  gap: 20px;
  padding: 16px 0;
  border-bottom: 1px solid var(--border);
}

.mastery-label {
  font-size: 15px;
  min-width: 200px;
}

.mastery-bar-bg {
  flex: 1;
  height: 6px;
  background: var(--bg-elevated);
  border-radius: 3px;
  overflow: hidden;
}

.mastery-bar {
  height: 100%;
  border-radius: 3px;
  background: linear-gradient(90deg, var(--accent), var(--antifragile-color));
  transition: width 1s var(--ease-out-expo);
}

.mastery-pct {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--text-muted);
  min-width: 40px;
  text-align: right;
}

/* ANIMATIONS */
@keyframes fadeUp {
  from { opacity: 0; transform: translateY(20px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

@keyframes modalIn {
  from { opacity: 0; transform: translateY(30px) scale(0.97); }
  to { opacity: 1; transform: translateY(0) scale(1); }
}

@keyframes scrollPulse {
  0% { top: -40px; }
  100% { top: 40px; }
}

/* RESPONSIVE */
@media (max-width: 768px) {
  .section { padding: 80px 20px 60px; }
  .nav-inner { padding: 0 20px; }
  .nav-tab span { display: none; }
  .hero { padding: 100px 20px 60px; }
  .hero-triad { gap: 24px; }
  .book-grid { grid-template-columns: 1fr; }
  .concepts-grid { grid-template-columns: 1fr; }
  .classifier-options { grid-template-columns: 1fr; }
  .stats-grid { grid-template-columns: repeat(2, 1fr); }
  .modal { padding: 32px 24px; }
}

/* CHAPTER PRIORITY & FILTER */
.chapter-priority {
  font-family: var(--font-mono);
  font-size: 10px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  padding: 3px 10px;
  border-radius: 3px;
  flex-shrink: 0;
}
.chapter-priority.must-read {
  background: var(--antifragile-glow);
  color: var(--antifragile-color);
  border: 1px solid var(--antifragile-color);
}
.chapter-priority.optional {
  background: var(--robust-glow);
  color: var(--robust-color);
  border: 1px solid var(--robust-color);
}
.chapter-oneliner {
  font-size: 13px;
  color: var(--text-muted);
  font-style: italic;
  margin-top: 4px;
  line-height: 1.5;
}
.chapter-filter {
  display: flex;
  gap: 8px;
  margin-bottom: 24px;
}
.chapter-filter-btn {
  font-family: var(--font-mono);
  font-size: 10px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  padding: 6px 14px;
  border: 1px solid var(--border);
  border-radius: 4px;
  background: none;
  color: var(--text-muted);
  cursor: pointer;
  transition: all 0.2s ease;
}
.chapter-filter-btn:hover { border-color: var(--text-secondary); color: var(--text-secondary); }
.chapter-filter-btn.active { border-color: var(--accent); color: var(--accent); background: var(--accent-dim); }
.book-card-meta {
  display: flex;
  gap: 12px;
  margin-top: 12px;
  font-family: var(--font-mono);
  font-size: 11px;
}
.book-card-meta .meta-must { color: var(--antifragile-color); }
.book-card-meta .meta-optional { color: var(--robust-color); }