/* 连续长文的可见章节锚点；不隐藏或切换正文。 */
.section-nav-scope { --section-nav-height: 50px; }
.section-nav, .section-nav * { box-sizing: border-box; }
.section-nav {
  position: sticky;
  top: var(--section-nav-top, 0px);
  z-index: 20;
  display: grid;
  grid-template-columns: repeat(var(--section-nav-columns, 8), minmax(0, 1fr));
  border: 1px solid var(--color-border);
  background: var(--color-bg);
  box-shadow: var(--shadow-sm);
}
.section-nav a {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  min-width: 0;
  min-height: 48px;
  padding: 10px 6px;
  border-bottom: 3px solid transparent;
  color: var(--color-surface-deep);
  font: 500 var(--fs-body)/1.5 var(--font-body);
  text-decoration: none;
  overflow-wrap: anywhere;
}
.section-nav a + a { border-left: 1px solid var(--color-border); }
.section-nav a:hover { background: var(--color-white); }
.section-nav a[aria-current="location"] {
  background: var(--color-surface-deep);
  border-bottom-color: var(--color-accent);
  color: var(--color-white);
}
.section-nav a:focus-visible { outline: 3px solid var(--color-accent); outline-offset: -3px; }
.section-nav__number { font-size: 11px; opacity: .75; font-variant-numeric: tabular-nums; }
@media (max-width: 900px) {
  .section-nav-scope { --section-nav-height: 98px; }
  .section-nav { grid-template-columns: repeat(4, minmax(0, 1fr)); }
  .section-nav a { font-size: 14px; }
  .section-nav a:nth-child(n + 5) { border-top: 1px solid var(--color-border); }
  .section-nav a:nth-child(4n + 1) { border-left: 0; }
  .section-nav__number { display: none; }
}