/* ==========================================================================
   Reading navigation (assets/js/reading-nav.js).
   The returning header and the current-section line under it (narrower
   screens).
   ========================================================================== */

/* Header: stays at the top of the page, slides away while reading down */
.js .site-header {
  position: sticky;
  top: 0;
  z-index: 600; /* under the feedback panel, the hover label and the page transition */
  background: var(--color-bg);
  transition: transform var(--duration-base) var(--ease-out);
}
.js .site-header.is-hidden { transform: translateY(-100%); }

.reading-bar__list { list-style: none; padding: 0; margin: 0; }

.reading-link {
  position: relative;
  display: grid;
  grid-template-columns: 2.25em minmax(0, 1fr);
  align-items: baseline;
  padding: var(--space-1) 0 var(--space-1) var(--space-4);
  font-size: var(--text-caption);
  line-height: var(--leading-body);
  color: var(--color-text-muted);
  transition: color var(--duration-fast) ease;
}
.reading-link:hover { color: var(--color-text); }
.reading-link__num { font-family: var(--font-mono); font-size: var(--text-mono); }
.reading-link.is-current { color: var(--color-text); }
.reading-link.is-current::before {
  content: "";
  position: absolute;
  left: 0;
  top: 50%;
  width: 2px;
  height: 1em;
  background: var(--color-accent);
  transform: translateY(-50%);
}

/* Current-section line: hangs under the returning header, narrower screens only */
.reading-bar {
  position: absolute;
  left: 0;
  right: 0;
  top: 100%;
  display: none;
  background: var(--color-bg);
}
/* The same inset hairline as the header's own */
.reading-bar::after {
  content: "";
  position: absolute;
  left: var(--gutter);
  right: var(--gutter);
  bottom: 0;
  border-bottom: 1px solid var(--color-border);
}
.site-header.is-floating.has-reading:not(.is-hidden) .reading-bar { display: block; }
@media (min-width: 1024px) {
  .reading-bar { display: none !important; }
}
.reading-bar__toggle {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  min-height: 2.75rem;
  text-align: left;
  font-size: var(--text-caption);
  font-weight: var(--weight-medium);
}
.reading-bar__num { font-family: var(--font-mono); font-size: var(--text-mono); font-weight: 400; color: var(--color-text-muted); }
.reading-bar__text { flex: 1; min-width: 0; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.reading-bar__toggle .icon { transition: transform var(--duration-fast) ease; }
.reading-bar__toggle[aria-expanded="true"] .icon { transform: rotate(180deg); }
.reading-bar__menu {
  max-height: 60dvh;
  overflow-y: auto;
  padding-bottom: var(--space-3);
}
.reading-bar__menu[hidden] { display: none; }
.reading-bar .reading-link { min-height: 2.75rem; align-items: center; }