/* ============================================================
   导航 —— 所有家族共用（导航不做变体，家族皮肤可微调）
   ============================================================ */

.site-header {
  position: fixed;
  inset: 0 0 auto 0;
  z-index: 100;
  transition: background var(--duration) var(--ease-out),
              box-shadow var(--duration) var(--ease-out);
}
.site-header.is-scrolled {
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  box-shadow: 0 1px 0 var(--line);
}
.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-block: var(--space-sm);
}
.nav__brand {
  font-family: var(--font-display);
  font-size: var(--text-xl);
  letter-spacing: 0.06em;
}
.nav__links {
  display: flex;
  gap: var(--space-lg);
  font-size: var(--text-sm);
  letter-spacing: 0.14em;
  text-transform: uppercase;
}
.nav__links a { position: relative; padding-block: var(--space-3xs); }
.nav__links a::after {
  content: "";
  position: absolute;
  left: 0; bottom: 0;
  width: 100%; height: 1px;
  background: var(--accent);
  transform: scaleX(0);
  transform-origin: right;
  transition: transform var(--duration) var(--ease-out);
}
.nav__links a:hover::after { transform: scaleX(1); transform-origin: left; }
.nav__cta { padding: var(--space-2xs) var(--space-md); }
@media (max-width: 48rem) {
  .nav__links { display: none; }
}

/* 在 immersive hero（深色背景）之上时导航反白 */
.site-header--on-dark:not(.is-scrolled) { color: #fff; }
.site-header--on-dark:not(.is-scrolled) .btn { border-color: #fff; color: #fff; }