:root {
  --brand: #078A88;
  --brand-ink: #FFFFFF;
  --bg: #F5FBFA;
  --surface: #FFFFFF;
  --tint: #ECF7F6;
  --stroke: #E4F1EF;
  --fg: #0F2E2D;
  --fg-2: #456665;
  --fg-3: #6E8B89;
  --radius: 18px;
  color-scheme: light dark;
}
@media (prefers-color-scheme: dark) {
  :root {
    --brand: #0FA39D;
    --brand-ink: #06201F;
    --bg: #0B1717;
    --surface: #122222;
    --tint: #0F1E1E;
    --stroke: #1C3433;
    --fg: #EAF5F4;
    --fg-2: #A8C3C1;
    --fg-3: #8FA8A6;
  }
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font: 16px/1.7 -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Segoe UI", sans-serif;
}
a { color: var(--brand); }
img { max-width: 100%; }

html[data-lang="zh"] [lang="en"],
html[data-lang="en"] [lang="zh"] { display: none; }
.langswitch { display: none; }
html[data-lang] .langswitch { display: inline-flex; }
html[data-lang] .langswitch button { display: inline-block; }

.container { max-width: 960px; margin: 0 auto; padding: 0 20px; }
.prose { max-width: 760px; }

.skip { position: absolute; left: -9999px; }
.skip:focus { left: 12px; top: 12px; background: var(--surface); padding: 8px 12px; border-radius: 10px; z-index: 10; }

.topbar {
  position: sticky; top: 0; z-index: 5;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  -webkit-backdrop-filter: saturate(180%) blur(12px);
  backdrop-filter: saturate(180%) blur(12px);
  border-bottom: 1px solid transparent;
  transition: border-color .2s ease;
}
.topbar.is-scrolled { border-bottom-color: var(--stroke); }
.topbar__inner { display: flex; align-items: center; gap: 12px 20px; flex-wrap: wrap; padding-top: 14px; padding-bottom: 14px; }
.brand { display: inline-flex; align-items: center; gap: 10px; font-weight: 700; font-size: 18px; color: var(--fg); text-decoration: none; margin-right: auto; }
.brand__mark { border-radius: 7px; }
.topnav { display: flex; gap: 18px; flex-wrap: wrap; font-size: 15px; }
.topnav a { color: var(--fg-2); text-decoration: none; }
.topnav a[aria-current="page"] { color: var(--brand); font-weight: 600; }
.langswitch { border: 1px solid var(--stroke); border-radius: 999px; padding: 2px; background: var(--surface); }
.langswitch button {
  font: inherit; font-size: 13px; border: 0; background: transparent; color: var(--fg-2);
  padding: 3px 10px; border-radius: 999px; cursor: pointer;
}
.langswitch button[aria-pressed="true"] { background: var(--brand); color: var(--brand-ink); }

.hero { padding: 64px 0 48px; text-align: center; }
.eyebrow { color: var(--brand); font-weight: 600; font-size: 14px; margin: 0 0 10px; }
.hero h1 { font-size: clamp(34px, 6vw, 52px); line-height: 1.15; margin: 0 0 16px; letter-spacing: -.01em; }
.lede { color: var(--fg-2); font-size: 18px; margin: 0 auto 24px; max-width: 620px; }
.cta-row { display: flex; gap: 12px; justify-content: center; flex-wrap: wrap; }
.btn { display: inline-block; padding: 11px 20px; border-radius: 12px; font-weight: 600; text-decoration: none; }
.btn--primary { background: var(--brand); color: var(--brand-ink); }
.btn--ghost { border: 1px solid var(--stroke); background: var(--surface); }

.band { padding: 44px 0; }
.band--tint { background: var(--tint); }
.band--tight { padding-top: 12px; }
.band h2 { font-size: 24px; margin: 0 0 12px; }

.cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(210px, 1fr)); gap: 14px; }
.card { background: var(--surface); border: 1px solid var(--stroke); border-radius: var(--radius); padding: 20px; }
.card__icon { width: 40px; height: 40px; border-radius: 12px; display: grid; place-items: center; background: var(--tint); color: var(--brand); }
.card__icon svg { width: 22px; height: 22px; }
.card h3 { font-size: 17px; margin: 14px 0 6px; }
.card p { margin: 0; color: var(--fg-2); font-size: 15px; }

.panel { display: grid; grid-template-columns: 1fr 1fr; gap: 28px; align-items: start; }
@media (max-width: 720px) { .panel { grid-template-columns: 1fr; } }
.muted { color: var(--fg-3); }
.small { font-size: 14px; }
.factlist { list-style: none; margin: 0; padding: 0; background: var(--surface); border: 1px solid var(--stroke); border-radius: var(--radius); }
.factlist li { display: grid; gap: 2px; padding: 14px 18px; border-top: 1px solid var(--stroke); }
.factlist li:first-child { border-top: 0; }
.factlist span { color: var(--fg-2); font-size: 15px; }

.doclinks { list-style: none; margin: 0; padding: 0; display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: 14px; }
.doclinks a { display: grid; gap: 4px; height: 100%; padding: 18px 20px; text-decoration: none; color: var(--fg); background: var(--surface); border: 1px solid var(--stroke); border-radius: var(--radius); }
.doclinks span { color: var(--fg-2); font-size: 15px; }

.pagehead { padding: 36px 0 8px; }
.back { font-size: 14px; text-decoration: none; }
.pagehead h1 { font-size: 34px; margin: 10px 0 6px; }
.pagehead .lede { margin: 0; font-size: 16px; }
.doc { background: var(--surface); border: 1px solid var(--stroke); border-radius: var(--radius); padding: 8px 24px 20px; margin: 20px 0 40px; }
.doc h2 { font-size: 18px; margin: 28px 0 6px; }
.doc p { margin: 8px 0; overflow-wrap: anywhere; }
.meta { display: grid; gap: 8px; margin: 16px 0 8px; padding-bottom: 16px; border-bottom: 1px solid var(--stroke); }
.meta div { display: grid; grid-template-columns: 120px 1fr; gap: 12px; font-size: 15px; }
.meta dt { color: var(--fg-3); }
.meta dd { margin: 0; overflow-wrap: anywhere; }
@media (max-width: 520px) { .meta div { grid-template-columns: 1fr; gap: 0; } }
.callout { background: var(--tint); border-radius: 14px; padding: 4px 16px; margin: 16px 0; }

footer { border-top: 1px solid var(--stroke); padding: 28px 0 40px; margin-top: 24px; }
.footer__nav { list-style: none; display: flex; flex-wrap: wrap; gap: 8px 20px; padding: 0; margin: 0 0 12px; font-size: 14px; }
.footer__nav a { color: var(--fg-2); text-decoration: none; }
.footer__legal p { margin: 4px 0; font-size: 13px; }

@media (prefers-reduced-motion: reduce) { * { transition: none !important; } }