:root {
  color-scheme: light;
  --ink: #202629;
  --muted: #596168;
  --line: #e3e5e8;
  --accent: #087b67;
  --accent-soft: #f3f5f4;
}

* { box-sizing: border-box; }
html { scroll-padding-top: 94px; }
body {
  margin: 0;
  background: #fff;
  color: var(--ink);
  font: 15px/1.7 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "PingFang SC", "Microsoft YaHei", sans-serif;
}
a { color: var(--accent); text-underline-offset: 3px; }
a:hover { text-decoration-thickness: 2px; }
a:focus-visible { outline: 2px solid var(--accent); outline-offset: 5px; border-radius: 2px; }
p { margin: 0 0 16px; }
h1, h2 { margin: 0; font-weight: 650; letter-spacing: -.025em; }
h1 { max-width: 760px; font-size: clamp(30px, 4vw, 43px); line-height: 1.2; }
h2 { font-size: 23px; line-height: 1.3; }
strong { font-weight: 650; }

.skip-link { position: absolute; top: -80px; left: 16px; padding: 8px 12px; background: #fff; z-index: 100; }
.skip-link:focus { top: 12px; }
.site-header { position: sticky; top: 0; z-index: 10; background: #fff; border-bottom: 1px solid var(--line); }
.header-inner { max-width: 1120px; margin: auto; min-height: 76px; padding: 15px 32px; display: flex; align-items: center; justify-content: space-between; gap: 28px; }
.brand { display: inline-flex; flex: none; }
.brand img { display: block; width: 164px; height: auto; background: #fff; }
.site-nav { display: flex; align-items: center; gap: 26px; font-size: 13px; }
.site-nav a { color: var(--muted); text-decoration: none; }
.site-nav a[aria-current="page"] { color: var(--accent); font-weight: 650; }

main { max-width: 1000px; margin: auto; padding: 58px 32px 42px; }
.eyebrow { margin-bottom: 12px; color: var(--muted); font-size: 11px; font-weight: 650; letter-spacing: .1em; text-transform: uppercase; }
.introduction > p:not(.eyebrow) { max-width: 760px; color: var(--muted); }
.introduction .lead { margin-top: 23px; color: var(--ink); font-size: 18px; line-height: 1.6; }
.intro-actions { display: flex; flex-wrap: wrap; gap: 12px; margin: 27px 0 40px; }
.button { display: inline-flex; gap: 14px; align-items: center; padding: 9px 15px; border: 1px solid var(--line); border-radius: 7px; color: var(--ink); text-decoration: none; font-size: 13px; font-weight: 550; }
.button:hover { border-color: var(--accent); }
.button.primary { border-color: var(--accent); background: var(--accent); color: #fff; }
.section-nav { display: flex; flex-wrap: wrap; gap: 12px 26px; padding: 16px 0; border-top: 1px solid var(--line); font-size: 12px; }
.section-nav a { text-decoration: none; }
.section-nav a:hover { text-decoration: underline; }
.method { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1.9fr); gap: 42px; padding: 38px 0; border-top: 1px solid var(--line); }
.section-heading .eyebrow { margin-bottom: 9px; color: var(--accent); }
.section-body { min-width: 0; color: var(--muted); }
.section-body p:last-of-type { margin-bottom: 13px; }
.citation-link { font-size: 12px; }
.references { border-top: 1px solid var(--line); padding-top: 34px; }
.references h2 { margin-bottom: 22px; }
.reference-list { padding-left: 22px; margin: 0; color: var(--muted); font-size: 13px; }
.reference-list li { margin: 0 0 17px; padding-left: 6px; overflow-wrap: anywhere; }
.reference-list li::marker { color: var(--ink); }
.reference-scope { margin: 22px 0 0; max-width: 730px; color: var(--muted); font-size: 12px; }
.site-footer { max-width: 936px; margin: 0 auto; padding: 21px 0 30px; display: flex; flex-wrap: wrap; justify-content: space-between; gap: 12px; border-top: 1px solid var(--line); color: var(--muted); font-size: 11px; }
.site-footer a { text-decoration: none; }

@media (max-width: 700px) {
  html { scroll-padding-top: 120px; }
  .header-inner { padding: 14px 20px; min-height: 70px; gap: 16px; }
  .brand img { width: 142px; }
  .site-nav { gap: 16px; font-size: 12px; }
  main { padding: 38px 22px 28px; }
  .introduction .lead { font-size: 17px; }
  .intro-actions { margin-bottom: 29px; }
  .section-nav { gap: 10px 20px; }
  .method { grid-template-columns: minmax(0, 1fr); gap: 19px; padding: 29px 0; }
  h2 { font-size: 22px; }
  .site-footer { margin: 0 22px; }
}

@media (max-width: 400px) {
  .header-inner { flex-wrap: wrap; gap: 11px; }
  .site-nav { width: 100%; justify-content: space-between; }
  .intro-actions { align-items: flex-start; flex-direction: column; }
}