/* Section navigation — sticky sub-nav for chapter sections */

.section-nav {
  position: sticky;
  top: var(--nav-height);
  z-index: 999;
  background-color: rgba(250, 250, 248, 0.97);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--color-border);
  box-shadow: var(--shadow-sm);
  opacity: 0;
  transform: translateY(-100%);
  transition: opacity 0.3s ease, transform 0.3s ease;
}

.section-nav--visible {
  opacity: 1;
  transform: translateY(0);
}

.section-nav__inner {
  display: flex;
  gap: var(--space-xs);
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-lg);
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: none;
}

.section-nav__inner::-webkit-scrollbar {
  display: none;
}

.section-nav__link {
  flex-shrink: 0;
  padding: var(--space-sm) var(--space-md);
  font-family: var(--font-body);
  font-size: var(--text-xs);
  font-weight: 500;
  color: var(--color-text-muted);
  text-decoration: none;
  white-space: nowrap;
  border-bottom: 2px solid transparent;
  transition: color 0.15s ease, border-color 0.15s ease;
}

.section-nav__link:hover {
  color: var(--color-primary);
}

.section-nav__link--active {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
  font-weight: 600;
}