:root {
  --bg: #ffffff;
  --fg: #1f2328;
  --muted: #6a737d;
  --border: #d0d7de;
  --link: #0969da;
}

html[data-bs-theme="dark"] {
  --bg: #0d1117;
  --fg: #e6edf3;
  --muted: #8b949e;
  --border: #30363d;
  --link: #58a6ff;
}

body {
  background: var(--bg);
  color: var(--fg);
}

a {
  color: var(--link);
}

.border {
  border-color: var(--border) !important;
}

article {
  background: var(--bg);
}

#sidebar {
  position: sticky;
  top: 1rem;
  max-height: calc(100vh - 2rem);
  overflow-y: auto;
  background: var(--bg);
}

.toc-link {
  display: block;
  padding: 0.25rem 0;
  text-decoration: none;
  color: var(--fg);
}

.toc-link:hover {
  text-decoration: underline;
}

/* Active section */
.toc-link.active {
  font-weight: 600;
  text-decoration: underline;
}

/* Collapsible indicators */
.toc-link.collapsible::before {
  content: "▸";
  display: inline-block;
  margin-right: 0.35rem;
  transform: translateY(-1px);
  transition: transform 0.15s ease;
}

.toc-link.open::before {
  transform: rotate(90deg);
}

/* Nested TOC spacing */
.toc ul {
  margin-left: 0.75rem;
}

/* Scroll to top button */
.scroll-top {
  position: fixed;
  right: 1.5rem;
  bottom: 1.5rem;
  z-index: 1030;
  display: none; /* shown via JS */
  border-radius: 999px;
  padding-inline: 0.9rem;
  padding-block: 0.55rem;
  font-size: 1.1rem;
  line-height: 1;
  box-shadow: 0 0.5rem 1rem rgba(0, 0, 0, 0.15);
}

/* Slightly stronger shadow in dark mode */
html[data-bs-theme="dark"] .scroll-top {
  box-shadow: 0 0.5rem 1rem rgba(0, 0, 0, 0.5);
}