/* ══════════════════════════════════════════
   READING PROGRESS BAR
   ══════════════════════════════════════════ */
#progress-bar {
  position: fixed;
  top: 0; left: 0;
  height: 2px;
  background: var(--accent);
  z-index: 1000;
  transition: width 0.1s linear;
  width: 0%;
}

/* ══════════════════════════════════════════
   SIDEBAR
   ══════════════════════════════════════════ */
#sidebar {
  position: fixed;
  top: 0; left: 0;
  width: var(--sidebar-width);
  height: 100vh;
  background: var(--bg-secondary);
  border-right: 1px solid var(--border);
  overflow-y: auto;
  z-index: 100;
  transition: transform var(--transition);
  display: flex;
  flex-direction: column;
}

#sidebar::-webkit-scrollbar { width: 4px; }
#sidebar::-webkit-scrollbar-track { background: transparent; }
#sidebar::-webkit-scrollbar-thumb { background: var(--border); border-radius: 2px; }

.sidebar-header {
  padding: 28px 24px 20px;
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
}

.sidebar-logo {
  font-family: var(--font-display);
  font-size: 18px;
  font-weight: 600;
  color: var(--text-primary);
  letter-spacing: -0.02em;
  cursor: pointer;
  display: block;
}

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

.sidebar-author {
  font-size: 12px;
  color: var(--text-tertiary);
  margin-top: 4px;
  font-weight: 400;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.sidebar-nav { padding: 16px 0; flex: 1; }

.nav-part { margin-bottom: 4px; margin-top: 8px; }
.nav-part:first-child { margin-top: 0; }

.nav-part-header {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 12px 24px 6px;
  font-size: 10px;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-tertiary);
  cursor: pointer;
  user-select: none;
  transition: color var(--transition);
  border-top: 1px solid var(--border);
}

.nav-part:first-child .nav-part-header { border-top: none; }

.nav-part-header:hover { color: var(--text-secondary); }

.nav-part-header .arrow {
  font-size: 8px;
  transition: transform var(--transition);
  opacity: 0.5;
}

.nav-part-header.collapsed .arrow { transform: rotate(-90deg); }

.nav-chapters {
  overflow: hidden;
  transition: max-height 0.4s ease;
  max-height: 2000px;
}

.nav-chapters.collapsed { max-height: 0 !important; }

.nav-chapter {
  display: flex;
  align-items: baseline;
  gap: 10px;
  padding: 6px 24px 6px 32px;
  font-size: 13px;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all var(--transition);
  border-left: 2px solid transparent;
  line-height: 1.45;
}

.nav-chapter span:last-child {
  flex: 1;
  min-width: 0;
  word-wrap: break-word;
  overflow-wrap: break-word;
}

.nav-chapter:hover {
  color: var(--text-primary);
  background: var(--accent-glow);
}

.nav-chapter.active {
  color: var(--accent);
  border-left-color: var(--accent);
  background: var(--accent-dim);
}

.nav-chapter-num {
  font-size: 11px;
  font-weight: 500;
  color: var(--text-tertiary);
  min-width: 18px;
  flex-shrink: 0;
}

.nav-chapter.active .nav-chapter-num { color: var(--accent); }

/* ══════════════════════════════════════════
   MOBILE MENU
   ══════════════════════════════════════════ */
#menu-toggle {
  display: none;
  position: fixed;
  top: 16px; left: 16px;
  width: 40px; height: 40px;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 8px;
  z-index: 200;
  cursor: pointer;
  align-items: center;
  justify-content: center;
  flex-direction: column;
  gap: 5px;
}

#menu-toggle span {
  display: block;
  width: 18px;
  height: 1.5px;
  background: var(--text-secondary);
  transition: all var(--transition);
}

#menu-toggle.active span:nth-child(1) { transform: rotate(45deg) translate(4.5px, 4.5px); }
#menu-toggle.active span:nth-child(2) { opacity: 0; }
#menu-toggle.active span:nth-child(3) { transform: rotate(-45deg) translate(4.5px, -4.5px); }

#sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.6);
  z-index: 90;
  backdrop-filter: blur(4px);
}

/* ══════════════════════════════════════════
   MAIN CONTENT
   ══════════════════════════════════════════ */
.main-content {
  margin-left: var(--sidebar-width);
  min-height: 100vh;
  transition: margin-left var(--transition);
}

/* ══════════════════════════════════════════
   HOMEPAGE
   ══════════════════════════════════════════ */
#homepage {
  padding: 80px 48px 120px;
  max-width: 1080px;
  margin: 0 auto;
}

.hero {
  margin-bottom: 80px;
  max-width: 680px;
}

.hero-badge {
  display: inline-block;
  font-size: 11px;
  font-weight: 500;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent);
  background: var(--accent-dim);
  padding: 5px 14px;
  border-radius: 4px;
  margin-bottom: 24px;
}

.hero h1 {
  font-family: var(--font-display);
  font-size: clamp(32px, 4.5vw, 46px);
  font-weight: 600;
  line-height: 1.2;
  color: var(--text-primary);
  margin-bottom: 20px;
  letter-spacing: -0.03em;
}

.hero h1 em {
  font-style: normal;
  color: var(--accent);
}

.hero-subtitle {
  font-size: 17px;
  color: var(--text-secondary);
  line-height: 1.7;
  max-width: 560px;
}

.hero-meta {
  margin-top: 28px;
  display: flex;
  gap: 32px;
  font-size: 13px;
  color: var(--text-tertiary);
}

.hero-meta-item {
  display: flex;
  align-items: center;
  gap: 6px;
}

.hero-meta-item strong {
  color: var(--text-secondary);
  font-weight: 500;
}

.hero-cta { margin-top: 36px; }

.hero-cta a {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 28px;
  background: var(--accent);
  color: var(--bg-primary);
  font-size: 14px;
  font-weight: 500;
  border-radius: 6px;
  transition: all var(--transition);
  letter-spacing: 0.01em;
}

.hero-cta a:hover {
  background: var(--accent-hover);
  transform: translateY(-1px);
  box-shadow: 0 4px 20px rgba(226,255,61,0.2);
}

.hero-cta a .arrow-icon { transition: transform var(--transition); }
.hero-cta a:hover .arrow-icon { transform: translateX(3px); }

/* Parts Grid */
.parts-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 16px;
}

.part-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 28px 26px;
  cursor: pointer;
  transition: all var(--transition);
  position: relative;
  overflow: hidden;
}

.part-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0;
  width: 100%; height: 2px;
  background: var(--accent);
  opacity: 0;
  transition: opacity var(--transition);
}

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

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

.part-card-number {
  font-size: 11px;
  font-weight: 500;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 10px;
}

.part-card-title {
  font-family: var(--font-display);
  font-size: 19px;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 10px;
  line-height: 1.35;
  letter-spacing: -0.02em;
}

.part-card-desc {
  font-size: 13.5px;
  color: var(--text-secondary);
  line-height: 1.6;
  margin-bottom: 16px;
}

.part-card-chapters { font-size: 12px; color: var(--text-tertiary); }
.part-card-chapters span { color: var(--text-secondary); }

/* ══════════════════════════════════════════
   CHAPTER VIEW
   ══════════════════════════════════════════ */
#chapter-view {
  display: none;
  padding: 60px 48px 120px;
  max-width: calc(var(--content-max) + 96px);
  margin: 0 auto;
}

.chapter-header {
  margin-bottom: 48px;
  padding-bottom: 32px;
  border-bottom: 1px solid var(--border);
}

.chapter-part-label {
  font-size: 12px;
  font-weight: 500;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 12px;
}

.chapter-number {
  font-family: var(--font-body);
  font-size: 13px;
  font-weight: 500;
  color: var(--text-tertiary);
  margin-bottom: 8px;
  letter-spacing: 0.02em;
}

.chapter-title {
  font-family: var(--font-display);
  font-size: clamp(26px, 3.5vw, 36px);
  font-weight: 600;
  line-height: 1.25;
  color: var(--text-primary);
  letter-spacing: -0.03em;
}

/* Chapter content */
.chapter-body {
  font-size: 18.5px;
  line-height: 1.8;
  color: var(--text-secondary);
}

.chapter-body h2 {
  font-family: var(--font-display);
  font-size: 24px;
  font-weight: 600;
  color: var(--text-primary);
  margin: 56px 0 18px;
  line-height: 1.35;
  letter-spacing: -0.02em;
}

.chapter-body h3 {
  font-family: var(--font-display);
  font-size: 19px;
  font-weight: 600;
  color: var(--text-primary);
  margin: 40px 0 14px;
  line-height: 1.4;
  letter-spacing: -0.01em;
}

.chapter-body p { margin-bottom: 24px; }
.chapter-body strong { color: var(--text-primary); font-weight: 500; }
.chapter-body em { color: var(--accent); font-style: italic; font-weight: 400; opacity: 0.85; }

.chapter-body blockquote {
  border-left: 2px solid var(--accent);
  padding: 4px 0 4px 24px;
  margin: 32px 0;
  color: var(--text-primary);
  font-family: var(--font-body);
  font-size: 18px;
  font-weight: 400;
  font-style: normal;
  line-height: 1.7;
  opacity: 0.9;
}

.chapter-body ul, .chapter-body ol {
  padding-left: 24px;
  margin-bottom: 20px;
}

.chapter-body li { margin-bottom: 8px; }

.chapter-body code {
  background: var(--bg-tertiary);
  padding: 2px 7px;
  border-radius: 4px;
  font-size: 0.9em;
}

.chapter-body hr {
  border: none;
  border-top: 1px solid var(--border);
  margin: 40px 0;
}

/* Placeholder state */
.chapter-placeholder {
  padding: 48px 32px;
  border: 1px dashed var(--border-light);
  border-radius: 8px;
  text-align: center;
  margin-top: 20px;
}

.chapter-placeholder-icon { font-size: 32px; margin-bottom: 16px; opacity: 0.3; }

.chapter-placeholder p {
  color: var(--text-tertiary);
  font-size: 14px;
  max-width: 480px;
  margin: 0 auto;
  line-height: 1.65;
}

.chapter-placeholder p.desc {
  color: var(--text-secondary);
  font-size: 15px;
  margin-top: 16px;
  font-style: italic;
}

/* Chapter Navigation */
.chapter-nav {
  display: flex;
  justify-content: space-between;
  align-items: stretch;
  gap: 16px;
  margin-top: 64px;
  padding-top: 32px;
  border-top: 1px solid var(--border);
}

.chapter-nav-btn {
  flex: 1;
  padding: 16px 20px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 8px;
  cursor: pointer;
  transition: all var(--transition);
  max-width: 50%;
}

.chapter-nav-btn:hover {
  background: var(--bg-card-hover);
  border-color: var(--border-light);
}

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

.chapter-nav-btn .nav-label {
  font-size: 11px;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--text-tertiary);
  margin-bottom: 4px;
}

.chapter-nav-btn .nav-title { font-size: 14px; color: var(--text-primary); font-weight: 500; }

.chapter-nav-btn.disabled { opacity: 0.3; pointer-events: none; }

/* ══════════════════════════════════════════
   NEWSLETTER
   ══════════════════════════════════════════ */
.newsletter-section {
  margin-top: 80px;
  padding: 48px;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 16px;
  text-align: center;
}

.newsletter-chapter {
  margin-top: 60px;
  padding: 36px 32px;
  border-radius: 12px;
}

.newsletter-inner { max-width: 560px; margin: 0 auto; }

.newsletter-icon { font-size: 28px; margin-bottom: 12px; opacity: 0.7; }

.newsletter-title {
  font-size: 20px; font-weight: 700;
  letter-spacing: -0.02em; color: var(--text-primary); margin-bottom: 8px;
}

.newsletter-title-sm {
  font-size: 17px; font-weight: 600;
  letter-spacing: -0.02em; color: var(--text-primary); margin-bottom: 8px;
}

.newsletter-desc {
  font-size: 14px; line-height: 1.6;
  color: var(--text-secondary); margin-bottom: 24px;
}

.newsletter-form {
  display: flex;
  gap: 8px;
  align-items: stretch;
}

.newsletter-form input,
.newsletter-form button {
  height: 44px;
  padding: 0 16px;
  font-family: var(--font-body);
  font-size: 14px;
  border-radius: 8px;
  border: none;
  box-sizing: border-box;
}

.newsletter-form input {
  flex: 1;
  min-width: 0;
  background: var(--bg-primary);
  border: 1px solid var(--border);
  color: var(--text-primary);
  outline: none;
  transition: border-color 0.2s;
}

.newsletter-form input:focus { border-color: var(--accent); }
.newsletter-form input::placeholder { color: var(--text-tertiary); }

.newsletter-form button {
  background: var(--accent);
  color: var(--bg-primary);
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
  white-space: nowrap;
  flex-shrink: 0;
}

.newsletter-form button:hover { background: #EAFF66; }
.newsletter-form button:disabled { opacity: 0.6; cursor: not-allowed; }

.newsletter-note {
  font-size: 11px; color: var(--text-tertiary); margin-top: 12px;
}

/* ══════════════════════════════════════════
   BACK TO TOP
   ══════════════════════════════════════════ */
.back-to-top {
  position: fixed;
  bottom: 32px;
  right: 32px;
  width: 42px;
  height: 42px;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 10px;
  color: var(--text-secondary);
  font-size: 18px;
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transition: all 0.25s ease;
  z-index: 90;
  display: flex;
  align-items: center;
  justify-content: center;
}

.back-to-top.visible {
  opacity: 1;
  visibility: visible;
}

.back-to-top:hover {
  background: var(--accent);
  color: var(--bg-primary);
  border-color: var(--accent);
}

/* ══════════════════════════════════════════
   SITE FOOTER
   ══════════════════════════════════════════ */
.site-footer {
  margin-top: 80px;
  padding: 32px 0;
  border-top: 1px solid var(--border);
  text-align: center;
  font-size: 12px;
  color: var(--text-tertiary);
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.site-footer a {
  color: var(--text-tertiary);
  text-decoration: none;
  transition: color 0.2s;
}

.site-footer a:hover { color: var(--accent); }

/* ══════════════════════════════════════════
   RESPONSIVE
   ══════════════════════════════════════════ */
@media (max-width: 900px) {
  #sidebar { transform: translateX(-100%); }
  #sidebar.open { transform: translateX(0); }
  #menu-toggle { display: flex; }
  #sidebar-overlay.active { display: block; }
  .main-content { margin-left: 0; }
  #homepage { padding: 80px 24px 80px; }
  #chapter-view { padding: 80px 24px 80px; }
  .parts-grid { grid-template-columns: 1fr; }
  .hero h1 { font-size: 28px; }
  .chapter-nav { flex-direction: column; }
  .chapter-nav-btn { max-width: 100%; }
  .newsletter-section { padding: 32px 20px; }
  .newsletter-form { flex-direction: column; }
  .newsletter-form input, .newsletter-form button { width: 100%; }
  .back-to-top { bottom: 20px; right: 20px; }
}

@media (max-width: 480px) {
  .hero-meta { flex-direction: column; gap: 8px; }
}

/* ══════════════════════════════════════════
   ANIMATIONS
   ══════════════════════════════════════════ */
@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(16px); }
  to { opacity: 1; transform: translateY(0); }
}

.animate-in {
  animation: fadeInUp 0.5s ease forwards;
  opacity: 0;
}

.animate-in:nth-child(1) { animation-delay: 0.05s; }
.animate-in:nth-child(2) { animation-delay: 0.1s; }
.animate-in:nth-child(3) { animation-delay: 0.15s; }
.animate-in:nth-child(4) { animation-delay: 0.2s; }
.animate-in:nth-child(5) { animation-delay: 0.25s; }
.animate-in:nth-child(6) { animation-delay: 0.3s; }
.animate-in:nth-child(7) { animation-delay: 0.35s; }
.animate-in:nth-child(8) { animation-delay: 0.4s; }