.site-header {
  position: sticky; top: 0; z-index: 40;
  background: color-mix(in srgb, var(--color-bg) 88%, transparent);
  backdrop-filter: blur(12px); border-bottom: 1px solid var(--color-line);
}
.site-header__inner { display: flex; align-items: center; justify-content: space-between; gap: var(--measure-xl); min-height: var(--header-h); padding-block: var(--measure-xs); }

.brand { display: flex; align-items: center; gap: var(--measure-xs); text-decoration: none; font-weight: var(--weight-bold); font-size: var(--text-lg); letter-spacing: var(--tracking-heading); }
.brand img { width: 36px; height: 36px; border-radius: var(--radius-round); background: var(--color-image-bg); transition: transform 0.6s var(--ease); }
.brand:hover img { transform: rotate(-20deg); }

.nav { display: flex; align-items: center; gap: 2px; }
.nav__link, .nav__trigger {
  display: inline-flex; align-items: center; gap: var(--measure-2xs); padding: var(--measure-xs) var(--measure-sm); border-radius: var(--radius-sm);
  color: var(--color-muted); font: inherit; font-size: var(--text-md); font-weight: var(--weight-medium); text-decoration: none;
  background: none; border: 0; cursor: pointer; transition: background 0.2s, color 0.2s;
}
.nav__link:hover, .nav__trigger:hover, .nav__trigger[aria-expanded="true"] { background: var(--color-tint); color: var(--color-ink); }
.nav__link[aria-current="page"], .nav__trigger.is-current { color: var(--color-ink); box-shadow: var(--shadow-underline); }
.nav__trigger svg { transition: transform 0.3s; }
.nav__trigger[aria-expanded="true"] svg { transform: rotate(180deg); }

.nav__menu { position: relative; }
.mega {
  position: absolute; top: calc(100% + var(--measure-sm)); left: calc(-1 * var(--measure-sm)); width: min(660px, 90vw);
  background: var(--color-surface); border: 1px solid var(--color-line); border-radius: var(--radius-lg);
  box-shadow: var(--shadow-paper); padding: var(--measure-sm);
  opacity: 0; visibility: hidden; transform: translateY(-8px);
  transition: opacity 0.25s, transform 0.25s var(--ease), visibility 0.25s;
}
.mega::before { content: ""; position: absolute; inset: -14px 0 auto; height: 14px; }
.nav__menu.is-open .mega { opacity: 1; visibility: visible; transform: none; }
@media (hover: hover) {
  .nav__menu:hover .mega { opacity: 1; visibility: visible; transform: none; }
}
.mega__grid { display: grid; grid-template-columns: 1fr 1fr; gap: 2px; }
.mega a { display: flex; gap: var(--measure-sm); align-items: flex-start; padding: var(--measure-sm) var(--measure-md); border-radius: var(--radius-sm); text-decoration: none; transition: background 0.2s; }
.mega a:hover, .mega a:focus-visible { background: var(--color-tint); }
.mega__num {
  flex: none; width: 26px; height: 26px; border-radius: var(--radius-sm); display: grid; place-items: center;
  background: var(--color-tint); color: var(--color-primary-text); font-size: var(--text-2xs); font-weight: var(--weight-semibold); transition: background 0.2s, color 0.2s;
}
.mega a:hover .mega__num { background: var(--color-primary); color: var(--color-on-primary); }
.mega strong { display: block; font-size: var(--text-sm); font-weight: var(--weight-semibold); }
.mega small { display: block; font-size: var(--text-xs); color: var(--color-muted); line-height: var(--leading-snug); }
.mega__foot { border-top: 1px dashed var(--color-line); margin-top: var(--measure-2xs); padding: var(--measure-sm) var(--measure-md) var(--measure-xs); }
.mega__foot a { display: inline-flex; padding: 0; color: var(--color-accent-text); font-weight: var(--weight-semibold); font-size: var(--text-sm); }
.mega__foot a:hover { background: none; }

.menu-toggle { display: none; }
.nav__mobile-cta { display: none !important; }

@media (max-width: 1040px) {
  .site-header { backdrop-filter: none; background: var(--color-bg); }
  .site-header__cta { display: none; }
  .menu-toggle {
    display: inline-flex; align-items: center; gap: var(--measure-xs); border: 1.5px solid var(--color-line); background: var(--color-surface);
    border-radius: var(--radius-sm); padding: var(--measure-sm) var(--measure-md); font-weight: var(--weight-semibold); cursor: pointer;
  }
  .nav {
    position: fixed; inset: var(--header-h) 0 0; z-index: 39; background: var(--color-bg);
    flex-direction: column; align-items: stretch; gap: var(--measure-2xs); padding: var(--measure-lg) var(--gutter) var(--measure-3xl); overflow-y: auto;
    opacity: 0; visibility: hidden; transform: translateY(-8px); transition: opacity 0.25s, transform 0.25s var(--ease), visibility 0.25s;
  }
  .site-header.is-open .nav { opacity: 1; visibility: visible; transform: none; }
  .nav__link, .nav__trigger { font-size: var(--text-lg); padding: var(--measure-md) var(--measure-sm); justify-content: space-between; width: 100%; }
  .mega { position: static; width: auto; box-shadow: none; border: 0; padding: 0 0 var(--measure-xs); display: none; opacity: 1; visibility: visible; transform: none; }
  .nav__menu.is-open .mega { display: block; }
  .nav__menu:hover .mega { display: none; }
  .nav__menu.is-open:hover .mega { display: block; }
  .mega__grid { grid-template-columns: 1fr; }
  .nav__mobile-cta { display: flex !important; margin-top: var(--measure-md); }
}