:root {
  --ink: #1a2332;
  --muted: #5a6578;
  --line: #d5dce8;
  --paper: #f5f7fb;
  --card: #ffffff;
  --accent: #1f6f6a;
  --accent-soft: #e6f3f1;
  --warn: #8a4b1f;
  --radius: 12px;
  --max: 820px;
  --font: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  --display: "Noto Serif SC", "Songti SC", serif;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: var(--font);
  color: var(--ink);
  background:
    radial-gradient(1200px 500px at 10% -10%, #dfeaf5 0%, transparent 55%),
    radial-gradient(900px 400px at 100% 0%, #e4f0ec 0%, transparent 50%),
    var(--paper);
  line-height: 1.75;
  font-size: 15px;
}

a {
  color: var(--accent);
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
}

a:hover {
  color: #155853;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  backdrop-filter: blur(10px);
  background: rgba(245, 247, 251, 0.88);
  border-bottom: 1px solid var(--line);
}

.site-header-inner {
  max-width: calc(var(--max) + 48px);
  margin: 0 auto;
  padding: 14px 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

.brand {
  font-family: var(--display);
  font-weight: 700;
  font-size: 1.05rem;
  letter-spacing: 0.02em;
  color: var(--ink);
  text-decoration: none;
}

.nav {
  display: flex;
  flex-wrap: wrap;
  gap: 8px 14px;
  font-size: 0.9rem;
}

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

.nav a:hover,
.nav a.active {
  color: var(--accent);
}

main {
  max-width: calc(var(--max) + 48px);
  margin: 0 auto;
  padding: 28px 24px 64px;
}

.hero {
  margin-bottom: 28px;
}

.hero h1 {
  font-family: var(--display);
  font-size: clamp(1.6rem, 3vw, 2.1rem);
  font-weight: 700;
  margin: 0 0 10px;
  letter-spacing: 0.03em;
}

.meta {
  color: var(--muted);
  font-size: 0.92rem;
  display: flex;
  flex-wrap: wrap;
  gap: 8px 18px;
}

.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 22px 22px 8px;
  margin-bottom: 20px;
  box-shadow: 0 8px 28px rgba(26, 35, 50, 0.04);
}

.card h2 {
  font-family: var(--display);
  font-size: 1.2rem;
  margin: 0 0 12px;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--line);
}

.card h3 {
  font-size: 1.02rem;
  margin: 22px 0 8px;
  color: #243247;
}

.card h4 {
  font-size: 0.98rem;
  margin: 16px 0 6px;
  color: #2c3a50;
}

.card p,
.card li {
  color: #2a3445;
}

.card p {
  margin: 0 0 12px;
}

.card ul,
.card ol {
  margin: 0 0 14px;
  padding-left: 1.3em;
}

.card li {
  margin-bottom: 6px;
}

.tip {
  background: var(--accent-soft);
  border: 1px solid #c5e2dd;
  border-radius: var(--radius);
  padding: 16px 18px;
  margin-bottom: 20px;
}

.tip strong {
  color: var(--accent);
}

.toc {
  columns: 1;
}

@media (min-width: 640px) {
  .toc {
    columns: 2;
    column-gap: 28px;
  }
}

.toc a {
  display: block;
  padding: 4px 0;
  color: var(--muted);
  text-decoration: none;
  break-inside: avoid;
}

.toc a:hover {
  color: var(--accent);
}

.toc a::before {
  content: "§ ";
  opacity: 0.45;
}

table {
  width: 100%;
  border-collapse: collapse;
  margin: 8px 0 18px;
  font-size: 0.92rem;
  overflow-x: auto;
  display: block;
}

th,
td {
  border: 1px solid var(--line);
  padding: 10px 12px;
  text-align: left;
  vertical-align: top;
  min-width: 90px;
}

th {
  background: #eef2f8;
  font-weight: 600;
  color: #243247;
}

tr:nth-child(even) td {
  background: #fafbfd;
}

.note {
  font-size: 0.9rem;
  color: var(--muted);
}

.foot {
  margin-top: 36px;
  padding-top: 18px;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: 0.88rem;
}

.config-warn {
  border-left: 3px solid var(--warn);
  background: #fff7ef;
  padding: 10px 14px;
  margin: 0 0 18px;
  color: var(--warn);
  font-size: 0.9rem;
  border-radius: 0 8px 8px 0;
}

.back-top {
  position: fixed;
  right: 18px;
  bottom: 18px;
  width: 42px;
  height: 42px;
  border-radius: 50%;
  border: 1px solid var(--line);
  background: var(--card);
  color: var(--ink);
  cursor: pointer;
  box-shadow: 0 6px 18px rgba(26, 35, 50, 0.08);
  display: grid;
  place-items: center;
  text-decoration: none;
  font-size: 1.1rem;
}

.back-top:hover {
  border-color: var(--accent);
  color: var(--accent);
}

@media (max-width: 560px) {
  .site-header-inner,
  main {
    padding-left: 16px;
    padding-right: 16px;
  }

  .card {
    padding: 16px 14px 4px;
  }
}