:root {
  --ink: #252b31;
  --muted: #626b73;
  --link: #225c8a;
  --link-dark: #143f61;
  --rule: #dfe3e6;
  --soft: #f6f8f9;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 28px; }
body {
  margin: 0;
  background: #fff;
  color: var(--ink);
  font: 15px/1.7 "Lato", -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
}
a { color: var(--link); text-underline-offset: 3px; }
a:hover { color: var(--link-dark); }
a:focus-visible { outline: 2px solid var(--link); outline-offset: 4px; }
h1, h2, h3 { line-height: 1.25; letter-spacing: -.35px; }
img { max-width: 100%; height: auto; }
code {
  padding: 2px 4px;
  border-radius: 2px;
  background: #f1f4f6;
  color: #344858;
  font: .86em/1.5 "Source Code Pro", ui-monospace, SFMono-Regular, Consolas, monospace;
}
pre {
  max-width: 100%;
  margin: 22px 0;
  padding: 16px 18px;
  overflow-x: auto;
  border: 1px solid var(--rule);
  background: var(--soft);
  font: 13px/1.7 "Source Code Pro", ui-monospace, SFMono-Regular, Consolas, monospace;
}
pre code { padding: 0; background: none; font-size: inherit; }

.skip-link { position: absolute; top: -60px; left: 16px; z-index: 10; padding: 8px 16px; background: #fff; }
.skip-link:focus { top: 8px; }
.container { width: calc(100% - 64px); max-width: 920px; margin: 0 auto; }

.site-header { border-bottom: 1px solid var(--rule); background: #fff; }
.nav { display: flex; align-items: center; justify-content: space-between; gap: 28px; min-height: 76px; }
.site-name { color: var(--ink); font-size: 17px; font-weight: 700; text-decoration: none; white-space: nowrap; }
.nav-links { display: flex; flex-wrap: wrap; gap: 24px; margin: 0; padding: 0; list-style: none; }
.nav-links a { display: block; padding: 6px 0; color: var(--muted); font-size: 14px; text-decoration: none; }
.nav-links a:hover { color: var(--link); text-decoration: underline; }

main { padding-top: 52px; padding-bottom: 24px; }
.hero { margin-bottom: 52px; }
.eyebrow { margin: 0 0 14px; color: var(--muted); font-size: 12px; font-weight: 700; letter-spacing: .8px; text-transform: uppercase; }
.hero h1 { margin: 0 0 12px; font-size: 52px; letter-spacing: -1.6px; }
.tagline { max-width: 720px; margin: 0 0 16px; color: #3f4850; font-size: 22px; line-height: 1.45; }
.lede { max-width: 720px; margin: 0 0 12px; font-size: 15.5px; line-height: 1.8; }
.hero-cn { margin: 0 0 22px; color: var(--muted); font-size: 14px; }
.hero-links { display: flex; flex-wrap: wrap; align-items: center; gap: 6px 20px; margin: 0; padding: 0; list-style: none; font-size: 14px; }
.hero-links a { text-decoration: underline; }
.button { display: inline-block; padding: 7px 13px; border: 1px solid var(--ink); color: var(--ink) !important; text-decoration: none !important; }
.button:hover { background: var(--ink); color: #fff !important; }

.section { margin: 0 0 48px; }
.section-head { display: flex; align-items: baseline; justify-content: space-between; gap: 16px; margin-bottom: 20px; padding-bottom: 9px; border-bottom: 1px solid var(--rule); }
.section-head h2 { margin: 0; font-size: 23px; letter-spacing: -.4px; }
.section-head span { color: var(--muted); font-size: 12px; white-space: nowrap; }
.section > p { max-width: 760px; }
.section-note { margin: 0; color: var(--muted); font-size: 13px; }
.section-note a { text-decoration: underline; }
.dot { padding: 0 7px; color: #a7adb3; }

.key-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 30px; }
.key-grid article { padding-top: 12px; border-top: 2px solid var(--ink); }
.key-grid h3 { margin: 0 0 6px; font-size: 17px; }
.key-grid p { margin: 0; color: #3f4850; font-size: 14px; line-height: 1.7; }
.section .section-note { margin-top: 18px; }

.diagram { margin: 0 0 16px; padding: 14px; border: 1px solid var(--rule); background: #fff; }
.diagram img { display: block; width: 100%; height: auto; }
.diagram figcaption { margin: 10px 2px 0; color: var(--muted); font-size: 12px; line-height: 1.65; }

.site-footer { border-top: 1px solid var(--rule); color: var(--muted); font-size: 12px; }
.site-footer .container { padding: 22px 0 28px; }
.site-footer p { margin: 0 0 4px; }
.site-footer strong { color: var(--ink); }

@media (max-width: 820px) {
  .key-grid { grid-template-columns: 1fr; gap: 22px; }
}
@media (max-width: 640px) {
  .container { width: calc(100% - 40px); }
  .nav { flex-direction: column; align-items: flex-start; gap: 8px; padding: 16px 0 12px; }
  .nav-links { gap: 8px 18px; }
  .nav-links a { font-size: 13px; }
  main { padding-top: 34px; }
  .hero h1 { font-size: 38px; }
  .tagline { font-size: 19px; }
  .section-head { align-items: flex-start; flex-direction: column; gap: 4px; }
  .section-head span { white-space: normal; }
  .diagram { padding: 8px; }
}