@layer components {
  .site-nav { display: flex; align-items: center; gap: var(--s-5); margin-inline-start: auto; }
  .nav-list { list-style: none; padding: 0; display: flex; align-items: center; gap: var(--s-1); }
  .nav-item { position: relative; }
  .nav-link {
    display: inline-flex; align-items: center; gap: var(--s-1); min-height: 44px; padding: 0 var(--s-3);
    color: var(--text); text-decoration: none; font-size: var(--t-sm); font-weight: 500; border-radius: var(--r-sm);
    position: relative; transition: color var(--dur-fast);
  }
  .nav-link::after {
    content: ""; position: absolute; left: var(--s-3); right: var(--s-3); bottom: 6px; height: 1.5px;
    background: var(--cyan); transform: scaleX(0); transform-origin: left; transition: transform var(--dur) var(--ease-out);
  }
  .nav-link:hover, .nav-item.is-active > .nav-link { color: var(--cyan); }
  .nav-link:hover::after, .nav-item.is-active > .nav-link::after { transform: scaleX(1); }
  .nav-link .icon-sm { transition: transform var(--dur-fast); }
  .nav-link[aria-expanded="true"] .icon-sm { transform: rotate(180deg); }

  /* 下拉：桌面 hover/focus-within + JS 点击；移动端展开为内嵌列表 */
  .sub {
    list-style: none; padding: var(--s-2); margin: 0; min-width: 200px;
    position: absolute; top: calc(100% + 4px); left: 0; z-index: 2;
    background: var(--raised); border: 1px solid var(--line-strong); border-radius: var(--r-md);
    box-shadow: var(--shadow-float), var(--hilite);
    opacity: 0; transform: translateY(-6px); pointer-events: none; visibility: hidden;
    transition: opacity var(--dur-fast) var(--ease-out), transform var(--dur-fast) var(--ease-out), visibility var(--dur-fast);
  }
  .sub a {
    display: flex; align-items: center; min-height: 40px; padding: 0 var(--s-3); border-radius: var(--r-sm);
    color: var(--text); text-decoration: none; font-size: var(--t-sm); white-space: nowrap;
  }
  .sub a:hover { background: var(--surface); color: var(--cyan); }
  .nav-item.has-sub:hover > .sub, .nav-item.has-sub:focus-within > .sub, .nav-item.has-sub.is-open > .sub {
    opacity: 1; transform: none; pointer-events: auto; visibility: visible;
  }

  .nav-tools { display: flex; align-items: center; gap: var(--s-2); }
  .nav-icon {
    display: inline-flex; align-items: center; justify-content: center; width: 44px; height: 44px;
    color: var(--text); border-radius: var(--r-sm); transition: color var(--dur-fast), background-color var(--dur-fast);
  }
  .nav-icon:hover { color: var(--cyan); background: var(--raised); }
  .nav-lang {
    display: inline-flex; align-items: center; justify-content: center; min-width: 44px; height: 36px; padding: 0 var(--s-2);
    font-family: var(--font-mono); font-size: var(--t-xs); letter-spacing: .08em; color: var(--muted);
    border: 1px solid var(--line-strong); border-radius: var(--r-sm); text-decoration: none;
  }
  .nav-lang:hover { color: var(--cyan); border-color: var(--cyan); }

  .nav-toggle { display: none; width: 44px; height: 44px; color: var(--text); margin-inline-start: auto; align-items: center; justify-content: center; border-radius: var(--r-sm); }
  .nav-toggle .icon-close { display: none; }
  .nav-toggle[aria-expanded="true"] .icon-open { display: none; }
  .nav-toggle[aria-expanded="true"] .icon-close { display: block; }

  @media (max-width: 1023px) {
    html.nav-open { overflow: hidden; }
    .nav-toggle { display: inline-flex; }
    .site-nav {
      position: fixed; inset: 64px 0 0 0; z-index: var(--z-nav); margin: 0;
      flex-direction: column; align-items: stretch; gap: 0; padding: var(--s-4) var(--gutter) var(--s-8);
      background: #070B12; overflow-y: auto;
      transform: translateX(100%); visibility: hidden; transition: transform var(--dur) var(--ease-out), visibility var(--dur);
    }
    .site-nav.is-open { transform: none; visibility: visible; }
    .nav-list { flex-direction: column; align-items: stretch; gap: 0; }
    .nav-item { border-bottom: 1px solid var(--line); }
    .nav-link { width: 100%; justify-content: space-between; min-height: 52px; font-size: var(--t-base); padding: 0 var(--s-1); }
    .nav-link::after { display: none; }
    .sub {
      position: static; min-width: 0; background: transparent; border: 0; box-shadow: none; padding: 0 0 var(--s-3) var(--s-4);
      opacity: 1; transform: none; visibility: visible; pointer-events: auto; display: none;
    }
    .nav-item.has-sub.is-open > .sub { display: block; }
    .nav-item.has-sub:hover > .sub:not(.is-open), .nav-item.has-sub:focus-within > .sub { display: none; }
    .nav-item.has-sub.is-open:hover > .sub, .nav-item.has-sub.is-open:focus-within > .sub { display: block; }
    .sub a { min-height: 44px; font-size: var(--t-sm); color: var(--muted); }
    .nav-tools { margin-top: var(--s-5); display: grid; grid-template-columns: 44px 1fr 2fr; gap: var(--s-3); }
    .nav-tools .btn { min-height: 44px; }
    .nav-lang { height: 44px; }
  }
}