/* ================================================================
   HANDBOOK.CSS — AI-Native Engineering Handbook styles
   Extends main.css with book-style navigation, TOC, diagrams, and CTAs.
   ================================================================ */

/* ----- Handbook index page ----- */
.handbook-index {
  padding-top: calc(var(--nav-height) + 64px);
  padding-bottom: 120px;
}

.handbook-index__hero {
  max-width: 760px;
  margin-bottom: 64px;
}

.handbook-index__hero .section__title {
  margin-top: 20px;
  margin-bottom: 16px;
}

.handbook-index__hero .section__subtitle {
  margin-bottom: 24px;
}

.handbook-index__intro {
  font-size: 1.1rem;
  line-height: 1.7;
  color: var(--text-secondary);
  max-width: 680px;
}

.handbook-index__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 24px;
  margin-bottom: 80px;
}

@media (min-width: 640px) {
  .handbook-index__grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

.handbook-index__card {
  display: flex;
  flex-direction: column;
  padding: 28px;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  text-decoration: none;
  transition: all 0.35s var(--ease-out);
}

.handbook-index__card:hover {
  border-color: rgba(var(--accent-rgb), 0.25);
  transform: translateY(-4px);
  box-shadow: 0 12px 36px rgba(var(--accent-rgb), 0.08);
}

.handbook-index__card-number {
  display: inline-block;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 12px;
}

.handbook-index__card-title {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 10px;
  line-height: 1.3;
}

.handbook-index__card-desc {
  font-size: 15px;
  color: var(--text-secondary);
  line-height: 1.6;
  margin-bottom: 16px;
  flex-grow: 1;
}

.handbook-index__card-meta {
  font-size: 13px;
  color: var(--text-muted);
  text-transform: capitalize;
}

.handbook-index__cta {
  margin-top: 0;
}

/* ----- Chapter hero ----- */
.handbook-page {
  padding-top: calc(var(--nav-height) + 48px);
}

.handbook-hero {
  margin-bottom: 32px;
}

.handbook-hero__badge {
  display: inline-block;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent);
  border: 1px solid var(--accent);
  padding: 5px 14px;
  border-radius: 100px;
  margin-bottom: 16px;
}

.handbook-hero__title {
  font-size: clamp(2rem, 5vw, 3rem);
  font-weight: 800;
  line-height: 1.1;
  letter-spacing: -0.03em;
  margin-bottom: 16px;
  color: var(--text-primary);
}

.handbook-hero__subtitle {
  font-size: clamp(1.1rem, 2.5vw, 1.35rem);
  color: var(--text-secondary);
  margin-bottom: 20px;
  line-height: 1.5;
}

.handbook-hero__meta {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px 16px;
  font-size: 14px;
  color: var(--text-muted);
}

.handbook-hero__dot {
  opacity: 0.4;
}

/* ----- Prerequisites box ----- */
.prerequisites-box {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 20px 24px;
  margin-bottom: 40px;
  max-width: 720px;
}

.prerequisites-box__title {
  font-size: 14px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-primary);
  margin-bottom: 10px;
}

.prerequisites-box ul {
  margin: 0;
  padding-left: 20px;
  color: var(--text-secondary);
}

.prerequisites-box li {
  margin-bottom: 4px;
}

.prerequisites-box a {
  color: var(--accent);
  text-decoration: none;
}

.prerequisites-box a:hover {
  text-decoration: underline;
}

/* ----- TL;DR override (first blockquote in body) ----- */
.handbook-body > blockquote:first-of-type {
  border-left: 4px solid var(--accent);
  background: var(--bg-secondary);
  padding: 24px;
  margin: 0 0 40px 0;
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  font-style: normal;
  color: var(--text-primary);
}

.handbook-body > blockquote:first-of-type p:last-child {
  margin-bottom: 0;
}

/* ----- Diagram panel (dark background for dark diagrams on light theme) ----- */
.diagram-panel {
  background: #0a1628;
  border-radius: var(--radius-lg);
  padding: 28px;
  margin: 32px 0;
  text-align: center;
  border: 1px solid #1e3a5f;
}

.diagram-panel img {
  max-width: 100%;
  height: auto;
  border-radius: var(--radius-sm);
  margin: 0 auto;
}

.diagram-panel figcaption {
  color: #8fa3bf;
  font-size: 14px;
  line-height: 1.5;
  margin-top: 16px;
  text-align: center;
}

/* ----- FAQ styling ----- */
.handbook-body h2:has(+ p strong) ~ p strong,
.handbook-body p:has(> strong) {
  /* No special rule needed; keep default */
}

/* ----- Chapter navigation ----- */
.chapter-nav {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
  margin-top: 64px;
  padding-top: 40px;
  border-top: 1px solid var(--border);
  max-width: 720px;
}

@media (max-width: 600px) {
  .chapter-nav {
    grid-template-columns: 1fr;
  }
}

.chapter-nav__link {
  display: block;
  padding: 20px;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  text-decoration: none;
  transition: all 0.25s ease;
}

.chapter-nav__link:hover {
  border-color: var(--accent);
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(var(--accent-rgb), 0.08);
}

.chapter-nav__link--next {
  text-align: right;
}

.chapter-nav__link--disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.chapter-nav__link--disabled:hover {
  border-color: var(--border);
  transform: none;
  box-shadow: none;
}

.chapter-nav__label {
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  margin-bottom: 8px;
}

.chapter-nav__title {
  font-size: 15px;
  font-weight: 600;
  color: var(--text-primary);
  line-height: 1.4;
}

/* ----- Sidebar / TOC ----- */
.handbook-sidebar {
  position: sticky;
  top: calc(var(--nav-height) + 32px);
  align-self: start;
}

.handbook-toc {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 20px;
}

.handbook-toc__title {
  font-size: 12px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  margin-bottom: 12px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--border);
}

.handbook-toc__list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.handbook-toc__list ul {
  list-style: none;
  padding-left: 12px;
  margin: 0;
}

.handbook-toc__list li {
  margin: 0;
}

.handbook-toc__link {
  display: block;
  padding: 6px 0;
  font-size: 13px;
  color: var(--text-secondary);
  text-decoration: none;
  border-left: 2px solid transparent;
  padding-left: 10px;
  line-height: 1.4;
  transition: all 0.2s ease;
}

.handbook-toc__link:hover {
  color: var(--accent);
  border-left-color: var(--accent);
}

/* ----- Glossary terms ----- */
.handbook-body h2#frequently-asked-questions + p,
.handbook-body h2#frequently-asked-questions ~ p {
  margin-bottom: 16px;
}

.handbook-body h2#frequently-asked-questions ~ p strong {
  color: var(--text-primary);
}

/* ----- Responsive: hide sidebar on small screens ----- */
@media (max-width: 900px) {
  .handbook-sidebar {
    display: none;
  }
}