/* ==========================================================================
   나만의 AI 스킬을 만들자 — E-Book Styles
   ========================================================================== */

/* ---------- Design Tokens ---------- */
:root {
  /* Colors */
  --color-bg: #FFF8F0;
  --color-bg-alt: #FFF1E3;
  --color-surface: #FFFFFF;
  --color-surface-hover: #FFF5EB;
  --color-primary: #E85D4A;
  --color-primary-hover: #D14A38;
  --color-primary-light: #FDEAE7;
  --color-secondary: #2B8C8C;
  --color-secondary-hover: #1F7070;
  --color-secondary-light: #E0F5F5;
  --color-text: #3D2B1F;
  --color-text-light: #6B5647;
  --color-text-muted: #9B8A7D;
  --color-border: #E8DDD4;
  --color-border-light: #F0E8E0;
  --color-code-bg: #2D2016;
  --color-code-text: #F5E6D3;
  --color-shadow: rgba(61, 43, 31, 0.08);
  --color-shadow-strong: rgba(61, 43, 31, 0.15);

  /* Typography */
  --font-body: 'Noto Sans KR', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Consolas', monospace;
  --text-xs: 0.75rem;
  --text-sm: 0.875rem;
  --text-base: 1rem;
  --text-lg: 1.125rem;
  --text-xl: 1.25rem;
  --text-2xl: 1.5rem;
  --text-3xl: 2rem;
  --text-4xl: 2.5rem;
  --text-5xl: 3.5rem;

  /* Spacing */
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;
  --space-24: 6rem;

  /* Layout */
  --sidebar-width: 280px;
  --content-max-width: 900px;
  --border-radius: 12px;
  --border-radius-sm: 8px;
  --border-radius-lg: 20px;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 400ms ease;
}

/* ---------- Dark Mode Tokens ---------- */
[data-theme="dark"] {
  --color-bg: #1A1410;
  --color-bg-alt: #231C15;
  --color-surface: #2A2118;
  --color-surface-hover: #332920;
  --color-primary: #F07A6A;
  --color-primary-hover: #E85D4A;
  --color-primary-light: #3D2520;
  --color-secondary: #3AADAD;
  --color-secondary-hover: #2B8C8C;
  --color-secondary-light: #1A3535;
  --color-text: #F0E4D8;
  --color-text-light: #C4B5A6;
  --color-text-muted: #8A7B6D;
  --color-border: #3D3228;
  --color-border-light: #332920;
  --color-code-bg: #0F0A06;
  --color-code-text: #F5E6D3;
  --color-shadow: rgba(0, 0, 0, 0.25);
  --color-shadow-strong: rgba(0, 0, 0, 0.4);
}

/* ---------- Reset & Base ---------- */
*, *::before, *::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
  text-size-adjust: 100%;
}

body {
  font-family: var(--font-body);
  font-weight: 400;
  line-height: 1.7;
  color: var(--color-text);
  background-color: var(--color-bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

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

img {
  max-width: 100%;
  height: auto;
  display: block;
}

button {
  font-family: inherit;
  border: none;
  background: none;
  cursor: pointer;
  color: inherit;
}

/* ---------- Progress Bar ---------- */
.progress-bar {
  position: fixed;
  top: 0;
  left: 0;
  width: 0%;
  height: 3px;
  background: linear-gradient(90deg, var(--color-primary), var(--color-secondary));
  z-index: 1000;
  transition: width 100ms linear;
}

/* ---------- Mobile Header ---------- */
.mobile-header {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 56px;
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
  z-index: 900;
  align-items: center;
  justify-content: space-between;
  padding: 0 var(--space-4);
  -webkit-backdrop-filter: blur(10px);
  backdrop-filter: blur(10px);
}

.mobile-title {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-text);
}

/* Hamburger Button */
.hamburger {
  width: 36px;
  height: 36px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  gap: 5px;
}

.hamburger span {
  display: block;
  width: 20px;
  height: 2px;
  background: var(--color-text);
  border-radius: 2px;
  transition: var(--transition-base);
}

.hamburger.active span:nth-child(1) {
  transform: rotate(45deg) translate(5px, 5px);
}

.hamburger.active span:nth-child(2) {
  opacity: 0;
}

.hamburger.active span:nth-child(3) {
  transform: rotate(-45deg) translate(5px, -5px);
}

/* ---------- Sidebar ---------- */
.sidebar {
  position: fixed;
  top: 0;
  left: 0;
  width: var(--sidebar-width);
  height: 100vh;
  background: var(--color-surface);
  border-right: 1px solid var(--color-border);
  z-index: 950;
  display: flex;
  flex-direction: column;
  transition: transform var(--transition-base);
  overflow: hidden;
}

.sidebar-header {
  padding: var(--space-6) var(--space-5);
  border-bottom: 1px solid var(--color-border-light);
  display: flex;
  align-items: center;
  gap: var(--space-3);
  flex-shrink: 0;
}

.sidebar-logo {
  font-size: 1.5rem;
}

.sidebar-title {
  font-size: var(--text-lg);
  font-weight: 700;
  flex: 1;
}

.sidebar-close {
  display: none;
  font-size: 1.5rem;
  width: 32px;
  height: 32px;
  align-items: center;
  justify-content: center;
  border-radius: var(--border-radius-sm);
}

.sidebar-close:hover {
  background: var(--color-bg-alt);
}

.sidebar-content {
  flex: 1;
  overflow-y: auto;
  padding: var(--space-4) 0;
  scrollbar-width: thin;
  scrollbar-color: var(--color-border) transparent;
}

.sidebar-content::-webkit-scrollbar {
  width: 4px;
}

.sidebar-content::-webkit-scrollbar-track {
  background: transparent;
}

.sidebar-content::-webkit-scrollbar-thumb {
  background: var(--color-border);
  border-radius: 4px;
}

.nav-list {
  list-style: none;
}

.nav-part {
  padding: var(--space-4) var(--space-5) var(--space-2);
  font-size: var(--text-xs);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-text-muted);
}

.nav-link {
  display: block;
  padding: var(--space-2) var(--space-5);
  font-size: var(--text-sm);
  color: var(--color-text-light);
  border-left: 3px solid transparent;
  transition: var(--transition-fast);
}

.nav-link:hover {
  color: var(--color-text);
  background: var(--color-bg-alt);
  border-left-color: var(--color-border);
}

.nav-link.active {
  color: var(--color-primary);
  background: var(--color-primary-light);
  border-left-color: var(--color-primary);
  font-weight: 600;
}

.sidebar-footer {
  padding: var(--space-4) var(--space-5);
  border-top: 1px solid var(--color-border-light);
  flex-shrink: 0;
}

/* Dark mode toggle */
.dark-mode-toggle {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-3);
  border-radius: var(--border-radius-sm);
  font-size: var(--text-sm);
  color: var(--color-text-light);
  transition: var(--transition-fast);
}

.dark-mode-toggle:hover {
  background: var(--color-bg-alt);
  color: var(--color-text);
}

.icon-moon { display: none; }
.icon-sun { display: block; }

[data-theme="dark"] .icon-moon { display: block; }
[data-theme="dark"] .icon-sun { display: none; }

.toggle-label {
  font-size: var(--text-sm);
}

/* Sidebar Overlay */
.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.4);
  z-index: 940;
  opacity: 0;
  transition: opacity var(--transition-base);
}

.sidebar-overlay.active {
  display: block;
  opacity: 1;
}

/* ---------- Main Content ---------- */
.main-content {
  margin-left: var(--sidebar-width);
  min-height: 100vh;
}

/* ---------- Hero Section ---------- */
.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-16) var(--space-8);
  overflow: hidden;
  background: linear-gradient(160deg, var(--color-bg) 0%, var(--color-bg-alt) 50%, var(--color-primary-light) 100%);
}

.hero-inner {
  max-width: 700px;
  text-align: center;
  position: relative;
  z-index: 2;
}

.hero-badge {
  display: inline-block;
  padding: var(--space-2) var(--space-4);
  background: var(--color-secondary-light);
  color: var(--color-secondary);
  font-size: var(--text-sm);
  font-weight: 600;
  border-radius: 100px;
  margin-bottom: var(--space-8);
  letter-spacing: 0.02em;
}

.hero-title {
  font-size: var(--text-5xl);
  font-weight: 900;
  line-height: 1.2;
  color: var(--color-text);
  margin-bottom: var(--space-6);
  word-break: keep-all;
}

.hero-title-sub {
  display: block;
  font-size: var(--text-xl);
  font-weight: 500;
  color: var(--color-text-light);
  margin-bottom: var(--space-2);
}

.hero-tagline {
  font-size: var(--text-lg);
  color: var(--color-text-light);
  line-height: 1.8;
  margin-bottom: var(--space-10);
  word-break: keep-all;
}

.hero-tagline strong {
  color: var(--color-primary);
  font-weight: 600;
}

/* Hero Buttons */
.hero-actions {
  display: flex;
  gap: var(--space-4);
  justify-content: center;
  flex-wrap: wrap;
  margin-bottom: var(--space-12);
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-3) var(--space-6);
  font-size: var(--text-base);
  font-weight: 600;
  border-radius: var(--border-radius);
  transition: var(--transition-base);
  white-space: nowrap;
}

.btn-primary {
  background: var(--color-primary);
  color: #FFF;
  box-shadow: 0 4px 14px rgba(232, 93, 74, 0.3);
}

.btn-primary:hover {
  background: var(--color-primary-hover);
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(232, 93, 74, 0.4);
}

.btn-secondary {
  background: var(--color-surface);
  color: var(--color-text);
  border: 2px solid var(--color-border);
}

.btn-secondary:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
  transform: translateY(-2px);
}

.btn-large {
  padding: var(--space-4) var(--space-8);
  font-size: var(--text-lg);
}

/* Hero Stats */
.hero-stats {
  display: flex;
  gap: var(--space-10);
  justify-content: center;
}

.stat {
  display: flex;
  flex-direction: column;
  align-items: center;
}

.stat-number {
  font-size: var(--text-3xl);
  font-weight: 900;
  color: var(--color-primary);
}

.stat-label {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  font-weight: 500;
}

/* Floating decorations */
.hero-decoration {
  position: absolute;
  inset: 0;
  pointer-events: none;
  z-index: 1;
}

.floating-shape {
  position: absolute;
  border-radius: 50%;
  opacity: 0.08;
  animation: float 20s ease-in-out infinite;
}

.shape-1 {
  width: 400px;
  height: 400px;
  background: var(--color-primary);
  top: -100px;
  right: -100px;
  animation-delay: 0s;
}

.shape-2 {
  width: 300px;
  height: 300px;
  background: var(--color-secondary);
  bottom: -80px;
  left: -80px;
  animation-delay: -7s;
}

.shape-3 {
  width: 200px;
  height: 200px;
  background: var(--color-primary);
  top: 50%;
  left: 60%;
  animation-delay: -14s;
}

@keyframes float {
  0%, 100% { transform: translate(0, 0) scale(1); }
  25% { transform: translate(30px, -30px) scale(1.05); }
  50% { transform: translate(-20px, 20px) scale(0.95); }
  75% { transform: translate(20px, 10px) scale(1.02); }
}

/* ---------- TOC Section ---------- */
.toc-section {
  padding: var(--space-20) var(--space-8);
  max-width: var(--content-max-width);
  margin: 0 auto;
}

.section-title {
  font-size: var(--text-4xl);
  font-weight: 900;
  text-align: center;
  margin-bottom: var(--space-3);
  color: var(--color-text);
}

.section-subtitle {
  text-align: center;
  color: var(--color-text-muted);
  font-size: var(--text-lg);
  margin-bottom: var(--space-16);
}

/* Part Headers */
.toc-part {
  margin-bottom: var(--space-16);
}

.part-header {
  margin-bottom: var(--space-8);
  padding-bottom: var(--space-6);
  border-bottom: 2px solid var(--color-border-light);
}

.part-number {
  display: inline-block;
  font-size: var(--text-sm);
  font-weight: 700;
  color: var(--color-primary);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  margin-bottom: var(--space-2);
}

.part-title {
  font-size: var(--text-2xl);
  font-weight: 800;
  margin-bottom: var(--space-2);
}

.part-desc {
  font-size: var(--text-base);
  color: var(--color-text-light);
}

/* Chapter Grid */
.chapter-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-5);
}

/* Chapter Cards */
.chapter-card {
  display: flex;
  gap: var(--space-5);
  padding: var(--space-6);
  background: var(--color-surface);
  border: 1px solid var(--color-border-light);
  border-radius: var(--border-radius);
  transition: var(--transition-base);
  cursor: pointer;
}

.chapter-card:hover {
  transform: translateY(-3px);
  box-shadow: 0 8px 30px var(--color-shadow);
  border-color: var(--color-primary);
}

.chapter-card:hover .chapter-title {
  color: var(--color-primary);
}

.chapter-card:hover .illustration-placeholder {
  transform: scale(1.08);
  background: var(--color-primary-light);
}

.chapter-illustration {
  flex-shrink: 0;
}

.illustration-placeholder {
  width: 72px;
  height: 72px;
  background: var(--color-bg-alt);
  border-radius: var(--border-radius);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 2rem;
  transition: var(--transition-base);
}

.chapter-info {
  flex: 1;
  min-width: 0;
}

.chapter-number {
  font-size: var(--text-xs);
  font-weight: 700;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.chapter-title {
  font-size: var(--text-xl);
  font-weight: 700;
  margin: var(--space-1) 0 var(--space-2);
  transition: color var(--transition-fast);
}

.chapter-excerpt {
  font-size: var(--text-sm);
  color: var(--color-text-light);
  line-height: 1.6;
}

/* Appendix Grid */
.appendix-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-4);
}

.appendix-card {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  padding: var(--space-5);
  background: var(--color-surface);
  border: 1px solid var(--color-border-light);
  border-radius: var(--border-radius);
  transition: var(--transition-base);
}

.appendix-card:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px var(--color-shadow);
  border-color: var(--color-secondary);
}

.appendix-icon {
  font-size: 1.75rem;
  flex-shrink: 0;
}

.appendix-card h4 {
  font-size: var(--text-sm);
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: var(--space-1);
}

.appendix-card p {
  font-size: var(--text-sm);
  color: var(--color-text-light);
}

/* ---------- CTA Section ---------- */
.cta-section {
  padding: var(--space-20) var(--space-8);
  background: linear-gradient(160deg, var(--color-primary-light) 0%, var(--color-bg) 100%);
}

.cta-inner {
  max-width: 600px;
  margin: 0 auto;
  text-align: center;
}

.cta-inner h2 {
  font-size: var(--text-3xl);
  font-weight: 900;
  margin-bottom: var(--space-4);
}

.cta-inner p {
  font-size: var(--text-lg);
  color: var(--color-text-light);
  margin-bottom: var(--space-8);
  line-height: 1.8;
}

/* ---------- Footer ---------- */
.site-footer {
  padding: var(--space-16) var(--space-8);
  background: var(--color-bg-alt);
  border-top: 1px solid var(--color-border-light);
}

.footer-inner {
  max-width: 600px;
  margin: 0 auto;
  text-align: center;
}

.footer-brand {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  font-size: var(--text-lg);
  font-weight: 700;
  margin-bottom: var(--space-6);
}

.footer-logo {
  font-size: 1.5rem;
}

.footer-message {
  font-size: var(--text-sm);
  color: var(--color-text-light);
  line-height: 1.8;
  margin-bottom: var(--space-6);
}

.footer-highlight {
  color: var(--color-primary);
  font-weight: 600;
}

.footer-links {
  margin-bottom: var(--space-6);
}

.footer-links a {
  font-size: var(--text-sm);
  color: var(--color-text-light);
  transition: color var(--transition-fast);
}

.footer-links a:hover {
  color: var(--color-primary);
}

.footer-divider {
  margin: 0 var(--space-3);
  color: var(--color-text-muted);
}

.footer-copy {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  line-height: 1.8;
}

.footer-copy a {
  color: var(--color-secondary);
}

.footer-copy a:hover {
  text-decoration: underline;
}

/* ==========================================================================
   Chapter Template Styles
   ========================================================================== */

/* Chapter Hero */
.chapter-hero {
  padding: var(--space-20) var(--space-8) var(--space-12);
  background: linear-gradient(160deg, var(--color-bg) 0%, var(--color-bg-alt) 100%);
  text-align: center;
}

.chapter-hero-inner {
  max-width: var(--content-max-width);
  margin: 0 auto;
}

.chapter-meta {
  font-size: var(--text-sm);
  font-weight: 700;
  color: var(--color-primary);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  margin-bottom: var(--space-3);
}

.chapter-hero h1 {
  font-size: var(--text-4xl);
  font-weight: 900;
  margin-bottom: var(--space-6);
  word-break: keep-all;
}

.chapter-illustration-large {
  width: 200px;
  height: 200px;
  margin: 0 auto;
  background: var(--color-surface);
  border-radius: var(--border-radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 5rem;
  box-shadow: 0 8px 30px var(--color-shadow);
  border: 1px solid var(--color-border-light);
}

/* Chapter Header */
.chapter-header {
  text-align: center;
  padding: var(--space-16) var(--space-8) var(--space-10);
  background: linear-gradient(160deg, var(--color-bg) 0%, var(--color-bg-alt) 100%);
  border-bottom: 2px solid var(--color-border-light);
  margin-bottom: var(--space-8);
}

.chapter-header h1 {
  font-size: var(--text-4xl);
  font-weight: 900;
  margin: var(--space-3) 0 var(--space-4);
  word-break: keep-all;
  color: var(--color-text);
}

.chapter-subtitle {
  font-size: var(--text-lg);
  color: var(--color-text-light);
  font-weight: 400;
}

/* Fun Box */
.fun-box {
  background: var(--color-secondary-light);
  border: 1px solid rgba(43, 140, 140, 0.2);
  border-radius: var(--border-radius);
  padding: var(--space-5) var(--space-6);
  margin-bottom: var(--space-6);
}

.fun-box-title {
  font-weight: 700;
  font-size: var(--text-sm);
  color: var(--color-secondary);
  margin-bottom: var(--space-2);
}

.fun-box p {
  font-size: var(--text-sm);
  line-height: 1.7;
}

/* Scenario Box */
.scenario-box {
  background: var(--color-bg-alt);
  border-left: 4px solid var(--color-primary);
  border-radius: 0 var(--border-radius) var(--border-radius) 0;
  padding: var(--space-5) var(--space-6);
  margin-bottom: var(--space-6);
  font-style: italic;
  font-size: var(--text-base);
  line-height: 1.8;
  color: var(--color-text-light);
}

/* Recap Box */
.recap-box {
  background: var(--color-primary-light);
  border: 1px solid rgba(232, 93, 74, 0.15);
  border-radius: var(--border-radius);
  padding: var(--space-6);
  margin: var(--space-10) 0 var(--space-6);
}

.recap-box h3,
.recap-box strong:first-child {
  font-size: var(--text-lg);
  font-weight: 700;
  color: var(--color-primary);
  margin-bottom: var(--space-3);
  display: block;
}

.recap-box ul {
  list-style: none;
  padding: 0;
}

.recap-box li {
  position: relative;
  padding-left: var(--space-5);
  margin-bottom: var(--space-2);
  font-size: var(--text-sm);
  line-height: 1.7;
}

.recap-box li::before {
  content: "✓";
  position: absolute;
  left: 0;
  color: var(--color-primary);
  font-weight: 700;
}

/* Next Teaser */
.next-teaser {
  background: var(--color-bg-alt);
  border-radius: var(--border-radius);
  padding: var(--space-5) var(--space-6);
  margin: var(--space-6) 0 var(--space-10);
  text-align: center;
  font-size: var(--text-sm);
  color: var(--color-text-light);
}

.next-teaser strong {
  color: var(--color-secondary);
}

/* Chapter Content */
.chapter-content {
  max-width: 720px;
  margin: 0 auto;
  padding: var(--space-12) var(--space-8);
}

.chapter-content h2 {
  font-size: var(--text-2xl);
  font-weight: 800;
  margin: var(--space-12) 0 var(--space-4);
  color: var(--color-text);
  padding-bottom: var(--space-3);
  border-bottom: 2px solid var(--color-border-light);
}

.chapter-content h3 {
  font-size: var(--text-xl);
  font-weight: 700;
  margin: var(--space-8) 0 var(--space-3);
}

.chapter-content p {
  margin-bottom: var(--space-4);
  font-size: var(--text-base);
  line-height: 1.85;
  word-break: keep-all;
}

.chapter-content ul,
.chapter-content ol {
  margin-bottom: var(--space-4);
  padding-left: var(--space-6);
}

.chapter-content li {
  margin-bottom: var(--space-2);
  line-height: 1.7;
}

.chapter-content strong {
  font-weight: 700;
  color: var(--color-text);
}

.chapter-content a {
  color: var(--color-primary);
  font-weight: 500;
  text-decoration: underline;
  text-decoration-color: rgba(232, 93, 74, 0.3);
  text-underline-offset: 3px;
  transition: var(--transition-fast);
}

.chapter-content a:hover {
  text-decoration-color: var(--color-primary);
}

/* Illustration Placeholder */
.illustration {
  margin: var(--space-10) 0;
  border-radius: var(--border-radius-lg);
  overflow: hidden;
  box-shadow: 0 10px 40px var(--color-shadow);
  border: 1px solid var(--color-border-light);
  background: var(--color-surface);
}

.illustration img {
  width: 100%;
  height: auto;
  transition: transform var(--transition-slow);
}

.illustration:hover img {
  transform: scale(1.02);
}

/* Code Blocks */
.chapter-content pre {
  background: var(--color-code-bg);
  color: var(--color-code-text);
  padding: var(--space-5);
  border-radius: var(--border-radius);
  overflow-x: auto;
  margin-bottom: var(--space-6);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  line-height: 1.7;
  border: 1px solid rgba(255, 255, 255, 0.05);
}

.chapter-content code {
  font-family: var(--font-mono);
  font-size: 0.9em;
  background: var(--color-bg-alt);
  padding: 0.15em 0.4em;
  border-radius: 4px;
  color: var(--color-primary);
}

.chapter-content pre code {
  background: none;
  padding: 0;
  color: var(--color-code-text);
  font-size: inherit;
}

/* Callout Boxes */
.callout {
  padding: var(--space-5) var(--space-6);
  border-radius: var(--border-radius);
  margin-bottom: var(--space-6);
  border-left: 4px solid;
}

.callout-tip {
  background: var(--color-secondary-light);
  border-left-color: var(--color-secondary);
}

.callout-warning {
  background: #FFF5E0;
  border-left-color: #E8A317;
}

[data-theme="dark"] .callout-warning {
  background: #352A15;
}

.callout-info {
  background: var(--color-primary-light);
  border-left-color: var(--color-primary);
}

.callout-title {
  font-weight: 700;
  font-size: var(--text-sm);
  margin-bottom: var(--space-2);
}

.callout p {
  font-size: var(--text-sm);
  margin-bottom: 0;
}

/* Chapter Navigation */
.chapter-nav {
  display: flex;
  justify-content: space-between;
  align-items: stretch;
  gap: var(--space-4);
  padding: var(--space-12) var(--space-8);
  max-width: 720px;
  margin: 0 auto;
  border-top: 2px solid var(--color-border-light);
}

.chapter-nav-link {
  flex: 1;
  padding: var(--space-5);
  background: var(--color-surface);
  border: 1px solid var(--color-border-light);
  border-radius: var(--border-radius);
  transition: var(--transition-base);
  display: flex;
  flex-direction: column;
  justify-content: center;
}

.chapter-nav-link:hover {
  border-color: var(--color-primary);
  transform: translateY(-2px);
  box-shadow: 0 6px 20px var(--color-shadow);
}

.chapter-nav-link.next {
  text-align: right;
}

.chapter-nav-label {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: var(--space-1);
}

.chapter-nav-title {
  font-size: var(--text-base);
  font-weight: 700;
  color: var(--color-text);
}

.back-to-toc {
  text-align: center;
  padding: var(--space-8);
}

.back-to-toc a {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  font-weight: 500;
  transition: color var(--transition-fast);
}

.back-to-toc a:hover {
  color: var(--color-primary);
}

/* ==========================================================================
   Responsive Design
   ========================================================================== */

/* Large Desktop */
@media (min-width: 1200px) {
  .chapter-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

/* Tablet */
@media (max-width: 1024px) {
  .sidebar {
    transform: translateX(-100%);
  }

  .sidebar.open {
    transform: translateX(0);
    box-shadow: 4px 0 30px var(--color-shadow-strong);
  }

  .sidebar-close {
    display: flex;
  }

  .mobile-header {
    display: flex;
  }

  .main-content {
    margin-left: 0;
    padding-top: 56px;
  }
}

/* Mobile */
@media (max-width: 640px) {
  :root {
    --text-5xl: 2.25rem;
    --text-4xl: 1.875rem;
    --text-3xl: 1.5rem;
    --text-2xl: 1.25rem;
  }

  .hero {
    padding: var(--space-12) var(--space-5);
    min-height: auto;
    padding-top: var(--space-16);
  }

  .hero-stats {
    gap: var(--space-6);
  }

  .toc-section {
    padding: var(--space-12) var(--space-5);
  }

  .chapter-card {
    padding: var(--space-4);
    gap: var(--space-4);
  }

  .illustration-placeholder {
    width: 56px;
    height: 56px;
    font-size: 1.5rem;
  }

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

  .chapter-nav {
    flex-direction: column;
    padding: var(--space-8) var(--space-5);
  }

  .chapter-nav-link.next {
    text-align: left;
  }

  .chapter-content {
    padding: var(--space-8) var(--space-5);
  }

  .chapter-hero {
    padding: var(--space-12) var(--space-5) var(--space-8);
  }

  .chapter-illustration-large {
    width: 140px;
    height: 140px;
    font-size: 3.5rem;
  }

  .cta-section {
    padding: var(--space-12) var(--space-5);
  }

  .site-footer {
    padding: var(--space-10) var(--space-5);
  }
}

/* ==========================================================================
   Print Styles
   ========================================================================== */
@media print {
  .progress-bar,
  .mobile-header,
  .sidebar,
  .sidebar-overlay,
  .dark-mode-toggle,
  .hero-actions,
  .cta-section,
  .chapter-nav,
  .back-to-toc,
  .hero-decoration {
    display: none !important;
  }

  .main-content {
    margin-left: 0 !important;
    padding-top: 0 !important;
  }

  body {
    background: #FFF;
    color: #000;
    font-size: 12pt;
    line-height: 1.5;
  }

  .hero {
    min-height: auto;
    padding: 2cm 0;
    background: none !important;
  }

  .hero-title {
    font-size: 28pt;
    color: #000;
  }

  .chapter-card {
    break-inside: avoid;
    border: 1px solid #CCC;
    box-shadow: none !important;
  }

  .chapter-card:hover {
    transform: none;
  }

  a {
    text-decoration: none;
    color: #000;
  }

  .chapter-content pre {
    border: 1px solid #CCC;
    background: #F5F5F5 !important;
    color: #000 !important;
  }

  .chapter-content pre code {
    color: #000 !important;
  }

  .toc-part {
    break-inside: avoid;
  }

  .site-footer {
    border-top: 1px solid #CCC;
    background: none;
  }
}

/* ==========================================================================
   Utilities & Animations
   ========================================================================== */

/* Fade-in on scroll */
.fade-in {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* Selection */
::selection {
  background: var(--color-primary-light);
  color: var(--color-text);
}

/* Focus styles */
:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
  border-radius: 4px;
}

/* Smooth color transitions for theme switching */
body,
.sidebar,
.chapter-card,
.appendix-card,
.mobile-header,
.hero,
.cta-section,
.site-footer {
  transition: background-color var(--transition-slow), color var(--transition-slow), border-color var(--transition-slow);
}