/* ============================================================
   LAYOUT — three-part documentation grid
   ============================================================ */

.book-layout {
  display: grid;
  grid-template-columns: var(--sidebar-w) minmax(0, 1fr) var(--toc-w);
  align-items: start;
  max-width: 1400px;
  margin: 0 auto;
}

.book-layout.no-toc {
  grid-template-columns: var(--sidebar-w) minmax(0, 1fr);
}

/* ---------- Sidebar ---------- */
.sidebar {
  position: sticky;
  top: var(--header-h);
  height: calc(100vh - var(--header-h));
  overflow-y: auto;
  padding: 2rem 1.25rem 3rem 1.5rem;
  border-right: 1px solid var(--border);
}

.sidebar-title {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.14em;
  color: var(--ink-faint);
  margin: 0 0 1rem;
}

.toc-chapter {
  border-bottom: 1px solid var(--border);
}

.toc-chapter:first-child {
  border-top: 1px solid var(--border);
}

.toc-chapter-btn {
  width: 100%;
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 0.5rem;
  background: none;
  border: none;
  text-align: left;
  padding: 0.65rem 0.15rem;
  font-family: var(--font-serif);
  font-size: 0.86rem;
  color: var(--ink);
}

.toc-chapter-btn:hover {
  color: var(--blue);
}

.toc-chapter-num {
  color: var(--ink-faint);
  font-family: var(--font-mono);
  font-size: 0.72rem;
  margin-right: 0.5rem;
}

.toc-caret {
  color: var(--ink-faint);
  font-size: 0.65rem;
  transition: transform 0.15s ease;
  flex-shrink: 0;
}

.toc-chapter.open .toc-caret {
  transform: rotate(90deg);
}

.toc-topics {
  list-style: none;
  margin: 0;
  padding: 0 0 0.6rem 0.4rem;
  display: none;
}

.toc-chapter.open .toc-topics {
  display: block;
}

.toc-topics li {
  border-left: 1px solid var(--border);
}

.toc-topics a {
  display: block;
  padding: 0.32rem 0 0.32rem 0.85rem;
  font-size: 0.83rem;
  color: var(--ink-muted);
  border-left: 2px solid transparent;
  margin-left: -1px;
}

.toc-topics a:hover {
  color: var(--blue);
  text-decoration: none;
}

.toc-topics a.active {
  color: var(--blue);
  border-left-color: var(--blue);
  font-weight: 600;
}

/* ---------- Main content column ---------- */
.content-col {
  min-width: 0;
  padding: 0 3rem;
}

.content-col .article-wrap,
.content-col .home-wrap {
  max-width: var(--content-max);
  margin: 0 auto;
  padding: 3rem 0 6rem;
}

/* ---------- Right "on this page" nav ---------- */
.page-toc {
  position: sticky;
  top: var(--header-h);
  height: calc(100vh - var(--header-h));
  overflow-y: auto;
  padding: 3rem 1.5rem 3rem 1rem;
  font-size: 0.8rem;
}

.page-toc-label {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.12em;
  color: var(--ink-faint);
  margin-bottom: 0.8rem;
}

.page-toc ol {
  list-style: none;
  margin: 0;
  padding: 0;
  border-left: 1px solid var(--border);
}

.page-toc li a {
  display: block;
  padding: 0.28rem 0 0.28rem 0.85rem;
  color: var(--ink-muted);
  border-left: 2px solid transparent;
  margin-left: -1px;
}

.page-toc li a:hover {
  color: var(--blue);
  text-decoration: none;
}

/* ---------- Mobile sidebar drawer ---------- */
.sidebar-backdrop {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(32, 38, 45, 0.35);
  z-index: 55;
}

@media (max-width: 1150px) {
  .book-layout,
  .book-layout.no-toc {
    grid-template-columns: var(--sidebar-w) minmax(0, 1fr);
  }
  .page-toc { display: none; }
}

@media (max-width: 900px) {
  .book-layout,
  .book-layout.no-toc {
    grid-template-columns: 1fr;
  }
  .sidebar {
    position: fixed;
    left: 0;
    top: var(--header-h);
    width: 82vw;
    max-width: 320px;
    background: var(--paper);
    z-index: 56;
    transform: translateX(-100%);
    transition: transform 0.2s ease;
    box-shadow: 6px 0 24px rgba(0,0,0,0.08);
  }
  .sidebar.open {
    transform: translateX(0);
  }
  body.sidebar-open .sidebar-backdrop {
    display: block;
  }
  .content-col {
    padding: 0 1.25rem;
  }
}

@media (max-width: 560px) {
  .content-col { padding: 0 1rem; }
}