:root {
  --page: #f4f7f4;
  --surface: #ffffff;
  --ink: #182523;
  --muted: #5b6d68;
  --line: #d4e0da;
  --deep: #173d3a;
  --green: #087f75;
  --green-soft: #e3f1eb;
  --coral: #c94b45;
  --coral-soft: #f8e5df;
  --amber: #e8a24b;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--page);
  color: var(--ink);
  font-family: "PingFang SC", "Microsoft YaHei", "Noto Sans CJK SC", sans-serif;
  line-height: 1.85;
}
nav.site-nav {
  position: sticky;
  top: 0;
  z-index: 10;
  border-bottom: 1px solid var(--line);
  background: rgba(255, 255, 255, .96);
}
.breadcrumbs {
  display: flex;
  align-items: center;
  gap: 16px;
  min-height: 48px;
  max-width: 1080px;
  margin: 0 auto;
  padding: 8px 16px;
  font-size: 14px;
}
a { color: var(--green); }
.site-nav a { color: var(--coral); text-decoration: none; transition: color 180ms ease; }
.site-nav a:hover { color: var(--green); }
a:focus-visible, summary:focus-visible { outline: 3px solid var(--amber); outline-offset: 3px; }
.article-shell { max-width: 980px; margin: 0 auto; padding: 32px 18px 72px; }
.article-hero {
  display: grid;
  grid-template-columns: minmax(0, 1.08fr) minmax(280px, .92fr);
  align-items: center;
  gap: 34px;
  overflow: hidden;
  margin-bottom: 26px;
  padding: 44px 40px 48px;
  border-radius: 8px;
  background: var(--deep);
  color: #fff;
}
.eyebrow { margin: 0 0 10px; color: #9dd4ca; font-size: 13px; font-weight: 700; }
h1, h2 { font-family: "Songti SC", SimSun, serif; text-wrap: balance; }
h1 { margin: 0 0 14px; font-size: clamp(34px, 5vw, 50px); line-height: 1.18; }
h2 { margin: 46px 0 15px; padding-bottom: 8px; border-bottom: 2px solid var(--coral); font-size: 28px; line-height: 1.35; }
h3 { margin: 26px 0 9px; font-size: 20px; line-height: 1.45; }
p { max-width: 44em; margin: 0 0 14px; text-wrap: pretty; }
.subtitle { color: #d9eee7; font-size: 18px; }
.meta { margin-top: 16px; color: #f2c5b7; font-size: 14px; font-variant-numeric: tabular-nums; }
.hero-diagram { display: block; width: 100%; height: auto; }
.quick-answer {
  margin: 20px 0;
  padding: 20px 22px;
  border: 1px solid var(--line);
  border-left: 6px solid var(--green);
  border-radius: 8px;
  background: var(--surface);
}
.quick-answer strong { color: var(--deep); }
.tag {
  display: inline-block;
  margin-bottom: 7px;
  padding: 2px 8px;
  border: 1px solid #ecc5bb;
  border-radius: 4px;
  background: var(--coral-soft);
  color: #943b37;
  font-size: 12px;
  font-weight: 700;
}
.toc {
  display: flex;
  flex-wrap: wrap;
  gap: 8px 18px;
  margin-bottom: 8px;
  padding: 16px 0 6px;
  border-bottom: 1px solid var(--line);
}
.toc a { font-size: 14px; font-weight: 700; text-decoration: none; }
.diagram {
  overflow: hidden;
  margin: 26px 0 30px;
  border: 1px solid #c8d9d1;
  border-radius: 8px;
  background: #eaf3ee;
}
.diagram svg { display: block; width: 100%; height: auto; }
.diagram figcaption {
  padding: 11px 16px 13px;
  border-top: 1px solid #c8d9d1;
  background: rgba(255, 255, 255, .7);
  color: var(--muted);
  font-size: 13px;
  line-height: 1.6;
}
.svg-label { font-family: "PingFang SC", "Microsoft YaHei", sans-serif; font-size: 19px; font-weight: 700; fill: var(--deep); }
.svg-note { font-family: "PingFang SC", "Microsoft YaHei", sans-serif; font-size: 14px; fill: #536a64; }
.table-wrap { overflow-x: auto; margin: 22px 0 28px; border: 1px solid var(--line); border-radius: 8px; background: var(--surface); }
table { width: 100%; min-width: 660px; border-collapse: collapse; }
th, td { padding: 14px 16px; border-bottom: 1px solid var(--line); text-align: left; vertical-align: top; }
th { background: var(--green-soft); font-size: 13px; }
tr:last-child td { border-bottom: 0; }
.callout { margin: 22px 0; padding: 18px 20px; border-left: 5px solid var(--amber); background: #fff8e8; }
.warning { border-left-color: var(--coral); background: #fff0ed; }
.evidence {
  margin: 18px 0;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
}
.evidence summary { cursor: pointer; padding: 15px 18px; color: var(--deep); font-weight: 700; }
.evidence p { padding: 0 18px 17px; color: var(--muted); }
.sources { margin-top: 46px; color: var(--muted); font-size: 14px; }
.sources li { margin-bottom: 8px; }
ol, ul { padding-left: 24px; }
li { margin-bottom: 7px; }
footer { max-width: 980px; margin: 0 auto 36px; padding: 0 18px; }

@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } }
@media (max-width: 720px) {
  .breadcrumbs { flex-wrap: wrap; gap: 6px 8px; font-size: 13px; }
  .breadcrumbs > * { white-space: nowrap; }
  .article-shell { padding: 20px 14px 56px; }
  .article-hero { grid-template-columns: 1fr; gap: 18px; padding: 30px 22px 28px; }
  .hero-diagram { max-width: 360px; margin: 0 auto; }
  h1 { font-size: 34px; }
  h2 { font-size: 25px; }
  .diagram { margin-inline: -2px; }
  .svg-label { font-size: 22px; }
  .svg-note { font-size: 18px; }
}