:root {
  color-scheme: light;
  --bg: #f5f6f1;
  --surface: #ffffff;
  --ink: #18211c;
  --muted: #5f6b63;
  --line: #d9dfd8;
  --accent: #176b4b;
  --accent-deep: #0f5339;
  --accent-weak: #e4f0e9;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: Arial, "PingFang SC", "Microsoft YaHei", sans-serif;
  line-height: 1.72;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--accent-deep); }
.container { width: min(980px, calc(100% - 40px)); margin: 0 auto; }
.skip-link { position: fixed; top: 8px; left: 8px; transform: translateY(-160%); background: #fff; padding: 8px 12px; z-index: 20; }
.skip-link:focus { transform: none; }
.site-header { border-bottom: 1px solid var(--line); background: rgba(245,246,241,.97); }
.header-inner { min-height: 72px; display: flex; align-items: center; justify-content: space-between; gap: 24px; }
.brand { color: var(--ink); font-size: 20px; font-weight: 800; text-decoration: none; }
.nav { display: flex; gap: 22px; flex-wrap: wrap; font-size: 14px; }
.hero { padding: 78px 0 58px; }
.eyebrow { color: var(--accent); font-weight: 800; letter-spacing: .08em; text-transform: uppercase; }
h1 { max-width: 850px; margin: 12px 0 20px; font-size: clamp(40px, 6vw, 68px); line-height: 1.08; letter-spacing: -.045em; }
.lead { max-width: 760px; color: #344139; font-size: 20px; }
.updated { color: var(--muted); font-size: 14px; }
.section { padding: 54px 0; border-top: 1px solid var(--line); }
h2 { margin: 0 0 16px; font-size: clamp(28px, 4vw, 42px); line-height: 1.18; letter-spacing: -.025em; }
h3 { margin: 0 0 10px; font-size: 21px; }
p { margin: 0 0 16px; }
.answer { max-width: 760px; font-size: 18px; }
.grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 18px; margin-top: 24px; }
.card { border: 1px solid var(--line); border-radius: 10px; background: var(--surface); padding: 24px; }
.card p:last-child { margin-bottom: 0; }
.boundary { border-left: 5px solid var(--accent); background: var(--accent-weak); padding: 22px 24px; }
.boundary strong { display: block; margin-bottom: 6px; }
table { width: 100%; border-collapse: collapse; margin: 22px 0; background: var(--surface); }
th, td { border: 1px solid var(--line); padding: 14px; text-align: left; vertical-align: top; }
th { background: var(--accent-weak); }
.feature-list { display: grid; gap: 14px; margin: 24px 0; }
.feature-link { display: block; border: 1px solid var(--line); border-radius: 8px; background: var(--surface); padding: 20px; text-decoration: none; }
.feature-link:hover, .feature-link:focus-visible { border-color: var(--accent); }
.feature-link span { display: block; margin-top: 6px; color: var(--muted); }
.faq details { border-top: 1px solid var(--line); padding: 18px 0; }
.faq summary { cursor: pointer; font-weight: 800; }
.faq details p { margin: 12px 0 0; max-width: 760px; }
.author { margin-top: 28px; border-top: 1px solid var(--line); padding-top: 18px; color: var(--muted); font-size: 14px; }
.site-footer { border-top: 1px solid var(--line); padding: 30px 0 42px; color: var(--muted); }
@media (max-width: 720px) {
  .header-inner { align-items: flex-start; flex-direction: column; padding: 16px 0; }
  .hero { padding-top: 52px; }
  .grid { grid-template-columns: 1fr; }
  th, td { padding: 10px; font-size: 14px; }
}