:root {
  color-scheme: dark;
  --background: #101516;
  --surface: #192123;
  --surface-soft: #141c1e;
  --text: #f0f5f1;
  --muted: #b5c3bf;
  --accent: #b8f3ce;
  --line: #354341;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 24px; }
body {
  margin: 0;
  background: radial-gradient(ellipse at 80% 0, #1c352e 0, transparent 38%), var(--background);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  font-size: 17px;
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--accent); text-underline-offset: 4px; }
a:hover { color: #e3ffec; }
a:focus-visible { outline: 3px solid var(--accent); outline-offset: 5px; border-radius: 3px; }
button, a { -webkit-tap-highlight-color: transparent; }
.wrap { width: min(1120px, calc(100% - 48px)); margin-inline: auto; }
.skip-link { position: absolute; left: 24px; top: -100px; padding: 10px 16px; background: var(--accent); color: var(--background); z-index: 10; }
.skip-link:focus { top: 12px; }
.topbar { display: flex; align-items: center; justify-content: space-between; gap: 24px; padding-block: 28px; border-bottom: 1px solid var(--line); }
.brand { display: inline-flex; align-items: center; gap: 11px; color: var(--text); font-size: 22px; font-weight: 750; text-decoration: none; letter-spacing: -0.6px; }
.brand img { display: block; width: 36px; height: 36px; border-radius: 10px; }
.topnav { display: flex; align-items: center; flex-wrap: wrap; justify-content: flex-end; gap: 20px; font-size: 14px; }
.topnav a { padding-block: 8px; text-decoration: none; }
.topnav [aria-current="page"] { color: var(--text); border-bottom: 1px solid var(--accent); }
.hero { display: grid; grid-template-columns: 1.35fr 1fr; align-items: center; gap: 70px; padding-block: 76px 68px; }
.eyebrow { margin: 0 0 16px; color: var(--accent); font-size: 12px; font-weight: 700; text-transform: uppercase; letter-spacing: 2px; }
h1 { margin: 0 0 24px; font-size: clamp(32px, 4.3vw, 52px); line-height: 1.16; font-weight: 730; letter-spacing: -1.8px; text-wrap: balance; }
.hero-intro { margin: 0 0 28px; color: var(--muted); font-size: 18px; line-height: 1.8; }
.button { display: inline-flex; align-items: center; justify-content: center; gap: 16px; min-height: 48px; padding: 10px 22px; border-radius: 10px; background: var(--accent); color: #12221b; font-size: 15px; font-weight: 700; text-decoration: none; }
.button:hover { background: #d2ffdf; color: #12221b; }
.button .arrow { font-size: 20px; line-height: 1; }
.sample { margin: 0; padding: 26px 28px 22px; border: 1px solid #50665c; border-radius: 20px; background: linear-gradient(155deg, #21302b, #192322); box-shadow: 0 22px 60px #0003; }
.sample figcaption { display: flex; align-items: center; justify-content: space-between; gap: 12px; margin-bottom: 16px; color: var(--muted); font-size: 13px; }
.sample-label { padding: 2px 9px; border: 1px solid #4a6157; border-radius: 100px; color: var(--accent); font-size: 11px; white-space: nowrap; }
.sample table { width: 100%; border-collapse: collapse; font-variant-numeric: tabular-nums; }
.sample th, .sample td { padding: 12px 0; border-bottom: 1px solid #3a4d46; }
.sample th { text-align: start; font-size: 15px; font-weight: 450; }
.sample td { text-align: end; font-size: 20px; }
.sample tfoot th, .sample tfoot td { padding-top: 20px; border: 0; color: var(--accent); font-weight: 700; }
.sample tfoot td { font-size: 36px; line-height: 1.25; letter-spacing: -1px; }
.sample-equation { margin: 18px 0 0; color: var(--muted); font-size: 13px; text-align: center; font-variant-numeric: tabular-nums; }
.content-layout { display: grid; grid-template-columns: 230px minmax(0, 1fr); gap: 70px; border-top: 1px solid var(--line); }
.contents { align-self: start; position: sticky; top: 24px; padding-top: 40px; }
.contents-title { margin: 0 0 12px; color: var(--muted); font-size: 12px; font-weight: 650; text-transform: uppercase; letter-spacing: 1.5px; }
.contents ol { margin: 0; padding: 0; list-style: none; counter-reset: contents; }
.contents li { counter-increment: contents; margin-bottom: 4px; }
.contents a { display: block; padding-block: 8px; font-size: 14px; line-height: 1.5; text-decoration: none; }
.contents a::before { content: counter(contents, decimal-leading-zero); display: inline-block; width: 28px; color: #8ba297; font-size: 11px; }
.article { min-width: 0; }
.article section { padding-block: 38px; border-bottom: 1px solid var(--line); }
.article section:last-child { border-bottom: 0; }
.section-number { display: block; margin-bottom: 10px; color: #8ba297; font-size: 12px; font-weight: 650; letter-spacing: 1.5px; }
h2 { margin: 0 0 18px; font-size: 27px; line-height: 1.4; font-weight: 680; letter-spacing: -0.6px; }
h3 { margin: 24px 0 10px; font-size: 19px; line-height: 1.5; font-weight: 650; }
p { margin: 0 0 18px; }
section > :last-child { margin-bottom: 0; }
.article p, .article li { color: #d1dbd6; }
.article strong { color: var(--text); font-weight: 650; }
.article ul, .article ol { margin: 16px 0 22px; padding-inline-start: 24px; }
.article li { padding-inline-start: 4px; margin-bottom: 10px; }
.math { display: block; padding: 19px 22px; margin-block: 18px; border: 1px solid var(--line); border-radius: 12px; background: var(--surface); color: var(--accent); font-size: 23px; font-weight: 550; line-height: 1.6; font-variant-numeric: tabular-nums; overflow-wrap: anywhere; }
.math small { display: block; margin-top: 4px; color: var(--muted); font-size: 14px; font-weight: 400; }
.example-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 10px; margin-block: 20px; }
.example-grid div { padding: 15px 18px; border: 1px solid var(--line); border-radius: 10px; background: var(--surface-soft); }
.example-grid span { display: block; color: var(--muted); font-size: 12px; }
.example-grid strong { display: block; margin-top: 4px; color: var(--accent); font-size: 21px; font-weight: 550; font-variant-numeric: tabular-nums; }
.note { padding: 18px 22px; border-inline-start: 3px solid var(--accent); border-radius: 0 10px 10px 0; background: var(--surface-soft); font-size: 15px; }
.key { display: inline-block; padding: 0 6px; border: 1px solid #54635d; border-radius: 4px; color: var(--text); font-size: 0.94em; white-space: nowrap; }
.download-links { display: flex; flex-wrap: wrap; gap: 12px 22px; margin-block: 22px; font-size: 15px; }
.end-cta { margin-top: 32px; padding: 28px; border: 1px solid var(--line); border-radius: 14px; background: var(--surface); }
.end-cta p { margin-bottom: 20px; }
.footer { display: flex; justify-content: space-between; align-items: center; flex-wrap: wrap; gap: 16px; padding-block: 28px; margin-top: 34px; border-top: 1px solid var(--line); color: var(--muted); font-size: 13px; }
.footer nav { display: flex; flex-wrap: wrap; gap: 20px; }
.footer a { text-decoration: none; }
html[lang="zh-CN"] h1 { line-height: 1.35; letter-spacing: -1px; }
html[lang="zh-CN"] .eyebrow, html[lang="zh-CN"] .contents-title { letter-spacing: 1px; }

@media (max-width: 900px) {
  .hero { gap: 36px; padding-block: 50px; }
  .content-layout { grid-template-columns: 180px minmax(0, 1fr); gap: 32px; }
  .sample { padding: 22px; }
}
@media (max-width: 680px) {
  .wrap { width: calc(100% - 36px); }
  .topbar { align-items: flex-start; gap: 18px; padding-block: 20px; }
  .brand { font-size: 19px; }
  .brand img { width: 30px; height: 30px; border-radius: 8px; }
  .topnav { gap: 8px 14px; font-size: 12px; }
  .topnav .home-link { display: none; }
  .hero { grid-template-columns: 1fr; gap: 30px; padding-block: 40px; }
  h1 { font-size: 35px; letter-spacing: -1.1px; }
  .hero-intro { font-size: 17px; }
  .sample { max-width: 420px; width: 100%; }
  .content-layout { display: block; }
  .contents { position: static; padding-block: 24px; border-bottom: 1px solid var(--line); }
  .contents ol { display: grid; grid-template-columns: 1fr 1fr; gap: 2px 16px; }
  .contents a { font-size: 13px; }
  .article section { padding-block: 30px; }
  h2 { font-size: 24px; }
  body { font-size: 16px; }
  .math { padding: 16px 18px; font-size: 21px; }
  .example-grid div { padding: 13px 14px; }
  .example-grid strong { font-size: 19px; }
  .end-cta { padding: 22px; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
}