:root {
  --ink: #0b1630;
  --ink-2: #17223d;
  --muted: #62708a;
  --blue: #2f66ee;
  --blue-dark: #1e4dcc;
  --blue-soft: #edf3ff;
  --cyan: #0ea5b7;
  --green: #12805c;
  --line: #dce3ee;
  --surface: #ffffff;
  --surface-alt: #f6f8fc;
  --nav-h: 72px;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 92px; }
body {
  margin: 0;
  color: var(--ink);
  background: var(--surface);
  font-family: Inter, "PingFang SC", "Microsoft YaHei", system-ui, sans-serif;
  font-size: 16px;
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
}
img { display: block; max-width: 100%; }
a { color: inherit; text-decoration: none; }
:focus-visible { outline: 3px solid rgba(47,102,238,.4); outline-offset: 3px; }
.container { width: min(1120px, calc(100% - 48px)); margin: 0 auto; }

.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  height: var(--nav-h);
  border-bottom: 1px solid rgba(220,227,238,.8);
  background: rgba(255,255,255,.94);
  backdrop-filter: blur(16px);
}
.nav { height: 100%; display: flex; align-items: center; justify-content: space-between; gap: 24px; }
.brand { display: flex; align-items: center; gap: 11px; font-weight: 800; }
.brand img { width: 38px; height: 38px; border-radius: 11px; object-fit: cover; }
.brand strong { display: block; line-height: 1.05; }
.brand small { display: block; margin-top: 4px; color: var(--muted); font-size: .7rem; letter-spacing: .1em; }
.nav-links { display: flex; align-items: center; gap: 24px; color: #42506a; font-size: .88rem; }
.nav-links a:hover { color: var(--blue); }
.nav-cta { padding: 9px 14px; border-radius: 9px; color: #fff !important; background: var(--blue); font-weight: 750; }

.hero {
  padding: 78px 0 68px;
  color: #fff;
  background: linear-gradient(135deg, #0b1630, #173a91 70%, #2859ca);
}
.crumbs { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 24px; color: #aebfe0; font-size: .78rem; }
.crumbs a:hover { color: #fff; }
.hero-grid { display: grid; grid-template-columns: minmax(0, 1.25fr) minmax(280px, .75fr); gap: 70px; align-items: end; }
.eyebrow { margin: 0 0 12px; color: #9bb7f6; font-size: .78rem; font-weight: 800; letter-spacing: .13em; text-transform: uppercase; }
.hero h1 { max-width: 820px; margin: 0 0 20px; font-size: clamp(2.55rem, 5vw, 4.5rem); line-height: 1.12; letter-spacing: -.045em; }
.hero-lead { max-width: 780px; margin: 0; color: #cbd7ed; font-size: 1.05rem; }
.definition-card { padding: 24px; border: 1px solid rgba(255,255,255,.18); border-radius: 18px; background: rgba(255,255,255,.08); }
.definition-card small { color: #9bb7f6; font-weight: 800; letter-spacing: .1em; }
.definition-card strong { display: block; margin-top: 8px; font-size: 1.08rem; }
.definition-card p { margin: 8px 0 0; color: #c4d0e7; font-size: .86rem; }
.updated { margin-top: 24px; color: #9eb0d0; font-size: .76rem; }

.content { padding: 58px 0 90px; background: var(--surface-alt); }
.article-layout { display: grid; grid-template-columns: 230px minmax(0,1fr); gap: 38px; align-items: start; }
.toc { position: sticky; top: 94px; display: grid; gap: 4px; padding: 16px; border: 1px solid var(--line); border-radius: 16px; background: #fff; }
.toc strong { margin: 3px 9px 8px; font-size: .82rem; }
.toc a { padding: 8px 9px; border-radius: 8px; color: var(--muted); font-size: .8rem; }
.toc a:hover { color: var(--blue-dark); background: var(--blue-soft); }
.toc .toc-cta { margin-top: 8px; color: #fff; background: var(--blue); text-align: center; font-weight: 750; }
.article { padding: 44px 48px; border: 1px solid var(--line); border-radius: 22px; background: #fff; box-shadow: 0 20px 50px rgba(17,38,82,.07); }
.article section { padding: 0 0 34px; margin: 0 0 34px; border-bottom: 1px solid var(--line); }
.article section:last-child { padding-bottom: 0; margin-bottom: 0; border-bottom: 0; }
.article h2 { margin: 0 0 14px; font-size: clamp(1.65rem, 3vw, 2.15rem); line-height: 1.25; letter-spacing: -.03em; }
.article h3 { margin: 24px 0 9px; font-size: 1.08rem; }
.article p { margin: 0 0 14px; color: #3f4d66; }
.article ul, .article ol { margin: 12px 0 0; padding-left: 22px; color: #3f4d66; }
.article li { margin: 8px 0; }
.answer { margin-bottom: 24px; padding: 19px 21px; border-left: 4px solid var(--blue); border-radius: 0 12px 12px 0; color: #26406e; background: var(--blue-soft); }
.answer strong { display: block; margin-bottom: 5px; color: #173a91; }
.compare { width: 100%; margin-top: 18px; border-collapse: collapse; font-size: .88rem; }
.compare th, .compare td { padding: 13px 14px; border: 1px solid var(--line); text-align: left; vertical-align: top; }
.compare th { color: #33415c; background: #f3f6fb; }
.compare td { color: #4f5d75; }
.check-grid { display: grid; grid-template-columns: repeat(2, minmax(0,1fr)); gap: 12px; margin-top: 18px; }
.check-card { padding: 18px; border: 1px solid var(--line); border-radius: 13px; background: #fbfcfe; }
.check-card b { display: block; margin-bottom: 6px; color: var(--blue-dark); font-size: .92rem; }
.check-card span { display: block; color: var(--muted); font-size: .84rem; }
.note { margin-top: 18px; padding: 16px 18px; border: 1px solid #cddcff; border-radius: 12px; color: #2a4b83; background: #f4f7ff; font-size: .86rem; }
.faq-list { display: grid; gap: 12px; margin-top: 18px; }
.faq-item { padding: 20px; border: 1px solid var(--line); border-radius: 14px; background: #fbfcfe; }
.faq-item h3 { margin: 0 0 7px; }
.faq-item p { margin: 0; font-size: .9rem; }

.hub { padding: 66px 0 90px; background: var(--surface-alt); }
.hub-head { max-width: 780px; margin-bottom: 38px; }
.hub-head h2 { margin: 0 0 14px; font-size: clamp(2rem, 4vw, 3.2rem); line-height: 1.2; letter-spacing: -.04em; }
.hub-head p { margin: 0; color: var(--muted); }
.topic-grid { display: grid; grid-template-columns: repeat(3, minmax(0,1fr)); gap: 15px; }
.topic-card { min-height: 250px; padding: 25px; border: 1px solid var(--line); border-radius: 18px; background: #fff; box-shadow: 0 15px 34px rgba(17,38,82,.05); transition: transform .2s ease, border-color .2s ease, box-shadow .2s ease; }
.topic-card:hover { transform: translateY(-4px); border-color: #b8c9f4; box-shadow: 0 22px 44px rgba(17,38,82,.1); }
.topic-card small { color: var(--blue); font-size: .72rem; font-weight: 800; letter-spacing: .1em; }
.topic-card h2, .topic-card h3 { margin: 42px 0 10px; font-size: 1.32rem; line-height: 1.3; letter-spacing: -.02em; }
.topic-card p { margin: 0; color: var(--muted); font-size: .88rem; }
.topic-card span { display: inline-block; margin-top: 22px; color: var(--blue-dark); font-size: .82rem; font-weight: 800; }
.hub-subhead { margin: 52px 0 24px; padding-top: 42px; border-top: 1px solid var(--line); }
.hub-subhead h2 { margin: 0 0 8px; font-size: clamp(1.65rem, 3vw, 2.3rem); }
.hub-subhead p { max-width: 760px; margin: 0; color: var(--muted); }
.related { padding: 52px 0; background: #fff; }
.related h2 { margin: 0 0 20px; font-size: 1.55rem; }
.related-links { display: grid; grid-template-columns: repeat(3, minmax(0,1fr)); gap: 12px; }
.related-links a { padding: 17px 18px; border: 1px solid var(--line); border-radius: 12px; color: #30405d; background: #fbfcfe; font-size: .88rem; font-weight: 700; }
.related-links a:hover { color: var(--blue-dark); border-color: #b8c9f4; }
.cta { padding: 66px 0; color: #fff; background: var(--blue); }
.cta-row { display: flex; align-items: center; justify-content: space-between; gap: 38px; }
.cta h2 { max-width: 680px; margin: 0 0 8px; font-size: clamp(1.9rem, 4vw, 3rem); line-height: 1.2; }
.cta p { max-width: 680px; margin: 0; color: #dbe6ff; }
.cta-actions { display: flex; gap: 10px; flex-wrap: wrap; }
.button { display: inline-flex; align-items: center; justify-content: center; min-height: 46px; padding: 0 18px; border: 1px solid rgba(255,255,255,.45); border-radius: 10px; color: #fff; font-weight: 800; white-space: nowrap; }
.button.primary { color: var(--blue-dark); border-color: #fff; background: #fff; }
.page-footer { padding: 36px 0; border-top: 1px solid var(--line); color: var(--muted); background: #fff; font-size: .8rem; }
.footer-row { display: flex; justify-content: space-between; gap: 24px; }
.footer-links { display: flex; gap: 16px; flex-wrap: wrap; }

@media (max-width: 900px) {
  .hero-grid, .article-layout { grid-template-columns: 1fr; }
  .definition-card { max-width: 700px; }
  .toc { position: static; grid-template-columns: repeat(3, minmax(0,1fr)); }
  .toc strong, .toc .toc-cta { grid-column: 1 / -1; }
  .topic-grid, .related-links { grid-template-columns: repeat(2, minmax(0,1fr)); }
  .cta-row { align-items: flex-start; flex-direction: column; }
}

@media (max-width: 620px) {
  .container { width: min(100% - 28px, 1120px); }
  .brand small { display: none; }
  .nav-links a:not(.nav-cta) { display: none; }
  .hero { padding: 52px 0 48px; }
  .hero h1 { font-size: 2.55rem; }
  .content, .hub { padding: 38px 0 60px; }
  .article { padding: 30px 22px; }
  .hub-subhead { margin-top: 38px; padding-top: 32px; }
  .toc, .check-grid, .topic-grid, .related-links { grid-template-columns: 1fr; }
  .toc strong, .toc .toc-cta { grid-column: auto; }
  .compare { display: block; overflow-x: auto; white-space: nowrap; }
  .footer-row { flex-direction: column; }
}