*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--bg); color: var(--ink);
  font-family: var(--font-sans); font-size: var(--step-0); line-height: 1.6; }
img { max-width: 100%; height: auto; display: block; }
a { color: var(--brand-ink); text-decoration: none; }
a:hover { text-decoration: underline; }
code, pre { font-family: var(--font-mono); }
.container { max-width: var(--maxw); margin-inline: auto; padding-inline: 20px; }
.skip-link { position: absolute; left: -999px; }
.skip-link:focus { left: 8px; top: 8px; background: #fff; padding: 8px; z-index: 100; }
.site-header { position: sticky; top: 0; background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(8px); border-bottom: 1px solid var(--line); z-index: 50; }
.site-header .bar { display: flex; align-items: center; gap: 24px; height: 64px; }
.site-nav { display: flex; gap: 16px; margin-left: auto; align-items: center; }
.nav-toggle { display: none; margin-left: auto; background: none; border: 0; padding: 6px; color: var(--ink); cursor: pointer; }
/* 二级下拉菜单 */
.nav-group { position: relative; }
.nav-trigger { display: inline-flex; align-items: center; gap: 4px; background: none; border: 0; padding: 0;
  font: inherit; color: var(--brand-ink); cursor: pointer; }
.nav-trigger .chev { transition: transform .16s; margin-top: 1px; }
.nav-trigger[aria-expanded="true"] .chev { transform: rotate(180deg); }
.nav-panel { position: absolute; top: calc(100% + 12px); left: 0; min-width: 264px;
  background: #fff; border: 1px solid var(--line); border-radius: 14px; box-shadow: var(--shadow-float);
  padding: 8px; display: grid; gap: 2px; z-index: 60;
  opacity: 0; visibility: hidden; transform: translateY(-6px);
  transition: opacity .16s ease, transform .16s ease, visibility .16s; }
.nav-panel::before { content: ""; position: absolute; top: -12px; left: 0; right: 0; height: 12px; }
.nav-panel-link { display: block; padding: 9px 12px; border-radius: 10px; }
.nav-panel-link:hover { background: var(--brand-wash); text-decoration: none; }
.nav-panel-link strong { display: block; font-size: 14px; color: var(--ink); font-weight: 600; }
.nav-panel-link span { display: block; font-size: 12.5px; color: var(--ink-soft); margin-top: 2px; }
.nav-trigger[aria-expanded="true"] + .nav-panel { opacity: 1; visibility: visible; transform: none; }
/* 功能分组大下拉 */
.nav-panel-mega { grid-template-columns: repeat(2, minmax(176px, 1fr)); gap: 6px 14px; min-width: 480px; padding: 12px; }
.nav-col { display: flex; flex-direction: column; }
.nav-col-head { display: inline-flex; align-items: center; gap: 5px; padding: 6px 10px;
  font-size: 12px; font-weight: 700; letter-spacing: .02em; text-transform: uppercase; color: var(--brand-ink); }
.nav-col-head:hover { text-decoration: none; }
.nav-col-head .icon { opacity: 0; transform: translateX(-3px); transition: opacity .16s, transform .16s; }
.nav-col-head:hover .icon { opacity: 1; transform: none; }
.nav-col-links { display: flex; flex-direction: column; }
.nav-sub-link { display: block; padding: 6px 10px; border-radius: 8px; font-size: 13px; color: var(--ink-soft); }
.nav-sub-link:hover { background: var(--brand-wash); color: var(--ink); text-decoration: none; }
@media (min-width: 801px) {
  .nav-group:hover .nav-panel, .nav-group:focus-within .nav-panel { opacity: 1; visibility: visible; transform: none; }
}
@media (max-width: 800px) {
  .nav-toggle { display: inline-flex; }
  .site-nav {
    display: none; position: absolute; top: 64px; left: 0; right: 0;
    flex-direction: column; align-items: flex-start; gap: 14px;
    background: var(--bg); border-bottom: 1px solid var(--line); padding: 16px 20px; margin: 0;
  }
  .site-nav.open { display: flex; }
  .nav-group { width: 100%; }
  .nav-trigger { width: 100%; justify-content: space-between; }
  .nav-panel { position: static; min-width: 0; padding: 4px 0 4px 12px; margin-top: 8px;
    border: 0; box-shadow: none; background: none; opacity: 1; visibility: visible; transform: none;
    display: none; transition: none; }
  .nav-panel::before { display: none; }
  .nav-trigger[aria-expanded="true"] + .nav-panel { display: grid; }
  .nav-panel-mega { grid-template-columns: 1fr; min-width: 0; padding: 4px 0 4px 12px; gap: 8px; }
  .nav-col-head { padding: 6px 4px; }
  .nav-sub-link { padding: 5px 4px; }
}
.btn { display: inline-flex; align-items: center; gap: 8px; padding: 11px 18px;
  border-radius: 11px; font-weight: 600; }
.btn-primary { background: var(--brand); color: #fff; }
.btn-primary:hover { background: var(--brand-ink); text-decoration: none; }
.site-footer { background: var(--dark); color: var(--dark-soft); margin-top: 80px; padding: 30px 0; font-size: 13.5px; }
.site-footer .fbar { display: flex; flex-wrap: wrap; gap: 12px 22px; align-items: center; justify-content: space-between; }
.site-footer a { color: var(--dark-soft); }
.site-footer a:hover { color: #fff; }
.site-footer .brand { color: #fff; font-family: var(--font-sans); font-weight: 700; letter-spacing: .06em; font-size: 15px; }
.site-footer .foot-links { display: flex; gap: 16px; }
.site-footer .foot-copy { font-family: var(--font-mono); font-size: 12px; }