// Collapsible left-sidebar sections (see sidebar-collapse.js).
//
// li.sc-group   chapter with nested ul.articles
// li.sc-open    nested list visible, caret rotated
// .sc-toggle    caret button, sits right of the chapter title

.book-summary li.chapter.sc-group {
  position: relative;
}

.book-summary li.chapter.sc-group > ul.articles {
  display: none;
}

.book-summary li.chapter.sc-group.sc-open > ul.articles {
  display: block;
}

.book-summary .sc-toggle {
  position: absolute;
  top: 9px;
  right: 6px;
  width: 18px;
  height: 18px;
  line-height: 18px;
  text-align: center;
  cursor: pointer;
  border-radius: 4px;
  user-select: none;
  opacity: 0.55;
  transition: opacity 0.15s, transform 0.15s;
}

.book-summary .sc-toggle::before {
  content: "\25B8"; /* right-pointing small triangle */
  font-size: 11px;
  color: inherit;
}

.book-summary .sc-toggle:hover,
.book-summary .sc-toggle:focus-visible {
  opacity: 1;
  outline: none;
}

.book-summary li.sc-group.sc-open > .sc-toggle {
  transform: rotate(90deg);
}

/* keep the caret clear of long titles */
.book-summary li.sc-group > a {
  padding-right: 24px;
}