.brand {
  display: inline-flex;
  min-height: 44px;
  align-items: center;
  gap: 5px;
  color: var(--color-text);
  font-size: 1.125rem;
  font-weight: 500;
  text-decoration: none;
  letter-spacing: -0.02em;
}
.brand strong { color: var(--color-text); font-weight: 500; }
.site-navigation > summary { display: none; }
.site-nav { display: grid; gap: 18px; }
.site-nav__group { min-width: 0; }
.site-nav__group h2 { padding: 0 12px; margin-bottom: 4px; color: var(--color-text-muted); font-size: 0.75rem; font-weight: 500; }
.site-nav__menu { display: grid; gap: 2px; }
.site-nav a { display: flex; min-height: 44px; align-items: center; gap: 10px; padding: 8px 10px; color: var(--color-text-muted); font-size: 0.8125rem; text-decoration: none; }
.site-nav__index { width: 20px; flex-shrink: 0; color: var(--color-text-muted); font-size: 0.75rem; font-variant-numeric: tabular-nums; }
.site-nav__link--active, .is-home .site-nav__home { background: var(--color-accent-soft); color: var(--color-text); }
.site-nav__group[data-nav-group="learning"] .site-nav__link--active { background: transparent; color: var(--color-text); }
.header-progress { display: flex; flex-wrap: wrap; gap: 8px 16px; color: var(--color-text-muted); font-size: 0.75rem; font-variant-numeric: tabular-nums; }
.header-progress__item { display: flex; align-items: baseline; gap: 8px; }
.header-progress strong { color: var(--color-text); font-weight: 500; }
@media (max-width: 820px) {
  .site-navigation > summary { display: inline-flex; min-height: 44px; align-items: center; padding: 0 12px; cursor: pointer; font-size: 0.8125rem; list-style: none; }
  .site-navigation > summary::-webkit-details-marker { display: none; }
  .site-nav { padding: 16px 0; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 16px 8px; }
  .site-nav__home { grid-column: 1 / -1; }
  .site-nav__index { display: none; }
  .site-nav a { padding: 8px; }
  .site-nav__group h2 { padding: 0 8px; }
}
@media (max-width: 420px) {
  .site-nav { grid-template-columns: 1fr; }
  .site-nav__menu { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}