/* RTD-style dropdown look on top of Furo's default colour scheme.
 *
 * Furo's light/dark theme switching is preserved untouched; only the
 * sidebar tree's *visual treatment* of expanded branches is restyled
 * to match the classic ReadTheDocs / stable-baselines3 look:
 *
 *   - No more chevron arrow icons.
 *   - When a branch is expanded, its children get a subtle highlight
 *     background that "scopes" the section, making the active page's
 *     context visible at a glance.
 *   - Toggle indicator (when present) becomes a `+` / `−` glyph rather
 *     than Furo's rotating arrow.
 *   - Captions stay in Furo's brand colour but tighten up the
 *     uppercase / letter-spacing for the RTD feel.
 *
 * Pairs with `expand-sidebar.js`, which forces every toctree-checkbox
 * outside the API-reference subtree open on load.
 */

/* ── Captions: tighter, uppercase, brand colour (no colour override) ── */
.sidebar-tree p.caption {
  margin-top: 1.25rem;
  margin-bottom: 0.4rem;
  font-size: 0.78rem;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  font-weight: 700;
}

/* ── Compact line-height in the tree ─────────────────────────────── */
.sidebar-tree li > a {
  line-height: 1.45;
  padding-top: 0.3rem;
  padding-bottom: 0.3rem;
}

/* ── Replace Furo's chevron toggle with a +/− glyph ──────────────── */
.sidebar-tree .toctree-checkbox + label .icon svg {
  display: none;
}
.sidebar-tree .toctree-checkbox + label::after {
  content: "+";
  display: inline-block;
  width: 1rem;
  height: 1rem;
  text-align: center;
  font-weight: 700;
  font-size: 0.95rem;
  line-height: 1;
}
.sidebar-tree .toctree-checkbox:checked + label::after {
  content: "−";
}

/* ── Expanded-branch highlight: the RTD "scoped" background bar ──── */
.sidebar-tree li.has-children > .toctree-checkbox:checked ~ ul {
  background: var(--color-background-secondary);
  margin-left: 0;
  padding-left: 1rem;
  border-left: 2px solid var(--color-background-border);
}

/* ── Active page: bold + same secondary background bleed ─────────── */
.sidebar-tree .current-page > a,
.sidebar-tree .reference.internal.current {
  background: var(--color-background-hover);
  font-weight: 600;
}

/* ── Drop the old guide-line indentation we used in the dark CSS ─── */
.sidebar-tree ul {
  border-left: none;
  margin-left: 0;
}

/* ── Landing page: logo replaces the H1 ──────────────────────────── */
.landing-logo {
  display: block;
  margin: 1.25rem auto 0.5rem !important;
}

/* Hide the H1 on the landing page only — Sphinx still uses it for the
 * document title, breadcrumbs, and TOC, but it doesn't render. */
article:has(.landing-logo) > section > h1:first-of-type {
  display: none;
}

/* Tagline directly under the logo: larger, bolder, lighter weight than
 * a heading — sets the project's pitch above the navigation grid. */
.landing-tagline {
  font-size: 1.15rem;
  font-weight: 600;
  text-align: center;
  margin: 0.5rem auto 2rem;
  max-width: 42rem;
  color: var(--color-foreground-secondary);
}