/* Mobile chapter marker: fixed in the existing left gutter, not in page flow. */
.section-indicator { display: none; }
@media (max-width: 899px) {
  .section-indicator {
    position: fixed;
    z-index: 25;
    top: 50%;
    left: 6px;
    display: none;
    flex-direction: column;
    align-items: flex-start;
    gap: 9px;
    transform: translateY(-50%);
    pointer-events: none;
  }
  .section-indicator span {
    display: block;
    width: 4px;
    height: 4px;
    border-radius: 4px;
    background: #89877d;
    box-shadow: 0 0 0 1px rgba(240, 235, 222, .3);
    transition: width 220ms ease, background-color 220ms ease;
  }
  .section-indicator span.is-current {
    width: 12px;
    background: var(--bg-inverted, #202522);
  }
  body:has(dialog[open]) .section-indicator { visibility: hidden; }
}
@media (prefers-reduced-motion: reduce) {
  .section-indicator span { transition: none; }
}