:root {
  color-scheme: light;
  --ink: #141414;
  --muted: #5c5c5c;
  --line: rgba(20, 20, 20, 0.12);
  --bg0: #f3f0ea;
  --bg1: #e7ece8;
  --card: rgba(255, 255, 255, 0.72);
  --accent: #1f4d3a;
  --max: 44rem;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  min-height: 100vh;
  font-family: "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  color: var(--ink);
  background:
    radial-gradient(1200px 500px at 10% -10%, #ffffffaa, transparent 60%),
    linear-gradient(165deg, var(--bg0), var(--bg1));
  line-height: 1.65;
}

a { color: var(--accent); text-underline-offset: 0.15em; }
a:hover { color: #163828; }

.shell {
  width: min(calc(100% - 2.5rem), 72rem);
  margin: 0 auto;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  backdrop-filter: blur(12px);
  background: rgba(243, 240, 234, 0.82);
  border-bottom: 1px solid var(--line);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  min-height: 3.75rem;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.55rem;
  color: inherit;
  text-decoration: none;
  font-weight: 650;
  letter-spacing: -0.02em;
}

.brand-mark {
  width: 1.35rem;
  height: 1.35rem;
}

.nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.85rem 1.1rem;
  font-size: 0.95rem;
}

.nav a {
  color: var(--ink);
  text-decoration: none;
}

.nav a[aria-current="page"],
.nav a:hover {
  color: var(--accent);
}

main {
  padding: 2.5rem 0 4rem;
}

.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 1.1rem;
  padding: clamp(1.4rem, 3vw, 2.2rem);
  box-shadow: 0 18px 40px rgba(20, 20, 20, 0.05);
}

.hero h1 {
  margin: 0 0 0.6rem;
  font-size: clamp(1.85rem, 4vw, 2.55rem);
  letter-spacing: -0.03em;
  line-height: 1.15;
}

.hero p,
.lead {
  margin: 0;
  color: var(--muted);
  max-width: 38rem;
}

.grid {
  display: grid;
  gap: 1rem;
  margin-top: 1.5rem;
}

@media (min-width: 780px) {
  .grid { grid-template-columns: 1fr 1fr; }
}

.doc-link {
  display: block;
  text-decoration: none;
  color: inherit;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 0.9rem;
  padding: 1.15rem 1.2rem;
  transition: border-color 0.15s ease, transform 0.15s ease;
}

.doc-link:hover {
  border-color: rgba(31, 77, 58, 0.45);
  transform: translateY(-1px);
}

.doc-link h2 {
  margin: 0 0 0.35rem;
  font-size: 1.15rem;
}

.doc-link p {
  margin: 0;
  color: var(--muted);
  font-size: 0.95rem;
}

.article {
  max-width: var(--max);
}

.article header {
  margin-bottom: 1.6rem;
}

.article h1 {
  margin: 0 0 0.5rem;
  font-size: clamp(1.7rem, 3.5vw, 2.2rem);
  letter-spacing: -0.03em;
}

.article section + section {
  margin-top: 1.35rem;
  padding-top: 1.35rem;
  border-top: 1px solid var(--line);
}

.article h2 {
  margin: 0 0 0.45rem;
  font-size: 1.05rem;
}

.article p {
  margin: 0;
  color: #2a2a2a;
}

.meta {
  margin-top: 1.8rem;
  color: var(--muted);
  font-size: 0.9rem;
}

.back {
  display: inline-block;
  margin-top: 1.2rem;
}

.site-footer {
  border-top: 1px solid var(--line);
  padding: 1.4rem 0 2rem;
  color: var(--muted);
  font-size: 0.9rem;
}

.footer-inner {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem 1.5rem;
  justify-content: space-between;
}

.footer-inner a { color: inherit; }