:root {
  --blue: #2f7fd6;
  --blue-deep: #1a5fad;
  --blue-soft: #e8f3fc;
  --ink: #1a2332;
  --muted: #5a6a7a;
  --line: #d7e3ef;
  --bg: #f4f8fc;
  --card: #ffffff;
  --accent: #0ea5a0;
  --radius: 14px;
  --shadow: 0 12px 40px rgba(26, 95, 173, 0.08);
  --max: 1120px;
  --font: "PingFang SC", "Hiragino Sans GB", "Noto Sans SC", "Microsoft YaHei", sans-serif;
  --display: "Source Han Sans SC", "PingFang SC", "Noto Sans SC", "Microsoft YaHei", sans-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%, #d6ebff 0%, transparent 55%),
    radial-gradient(900px 420px at 100% 0%, #c8f1ef 0%, transparent 50%),
    linear-gradient(180deg, #eef6ff 0%, var(--bg) 28%, #eef3f8 100%);
  line-height: 1.75;
  font-size: 16px;
}

img {
  max-width: 100%;
  height: auto;
  display: block;
}

a {
  color: var(--blue-deep);
  text-decoration: none;
}

a:hover {
  color: var(--blue);
  text-decoration: underline;
}

.container {
  width: min(100% - 32px, var(--max));
  margin: 0 auto;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  backdrop-filter: blur(12px);
  background: rgba(255, 255, 255, 0.88);
  border-bottom: 1px solid rgba(215, 227, 239, 0.9);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 12px 0;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  color: var(--ink);
  text-decoration: none;
  font-weight: 700;
  font-family: var(--display);
  letter-spacing: 0.02em;
}

.brand:hover {
  text-decoration: none;
  color: var(--blue-deep);
}

.brand img {
  width: 42px;
  height: 42px;
  border-radius: 10px;
  object-fit: cover;
}

.brand span {
  font-size: 1.05rem;
}

.nav {
  display: flex;
  flex-wrap: wrap;
  gap: 6px 14px;
  justify-content: flex-end;
}

.nav a {
  color: var(--muted);
  font-size: 0.92rem;
  font-weight: 600;
  text-decoration: none;
  padding: 6px 2px;
}

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

.hero {
  padding: 48px 0 28px;
}

.hero-grid {
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  gap: 36px;
  align-items: center;
}

.hero-copy h1 {
  margin: 0 0 14px;
  font-family: var(--display);
  font-size: clamp(1.8rem, 3.4vw, 2.6rem);
  line-height: 1.25;
  letter-spacing: 0.01em;
  color: var(--ink);
}

.hero-copy .lead {
  margin: 0 0 22px;
  color: var(--muted);
  font-size: 1.05rem;
  max-width: 36em;
}

.cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 12px 20px;
  border-radius: 999px;
  font-weight: 700;
  border: 1px solid transparent;
  text-decoration: none;
  transition: transform 0.2s ease, box-shadow 0.2s ease, background 0.2s ease;
}

.btn:hover {
  text-decoration: none;
  transform: translateY(-1px);
}

.btn-primary {
  background: linear-gradient(135deg, var(--blue) 0%, var(--blue-deep) 100%);
  color: #fff;
  box-shadow: 0 10px 24px rgba(47, 127, 214, 0.28);
}

.btn-primary:hover {
  color: #fff;
}

.btn-ghost {
  background: rgba(255, 255, 255, 0.8);
  border-color: var(--line);
  color: var(--blue-deep);
}

.hero-visual {
  position: relative;
}

.hero-visual img {
  width: 100%;
  max-width: 360px;
  margin: 0 auto;
  border-radius: 22px;
  box-shadow: var(--shadow);
  border: 1px solid rgba(255, 255, 255, 0.7);
}

.section {
  padding: 36px 0;
}

.section-head {
  margin-bottom: 20px;
}

.section-head h2 {
  margin: 0 0 8px;
  font-size: clamp(1.35rem, 2.4vw, 1.85rem);
  font-family: var(--display);
  line-height: 1.3;
}

.section-head p {
  margin: 0;
  color: var(--muted);
  max-width: 48em;
}

.prose {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 28px 28px 8px;
  box-shadow: var(--shadow);
}

.prose h2,
.prose h3 {
  font-family: var(--display);
  scroll-margin-top: 80px;
}

.prose h2 {
  margin: 8px 0 12px;
  font-size: 1.45rem;
  padding-bottom: 8px;
  border-bottom: 2px solid var(--blue-soft);
}

.prose h3 {
  margin: 22px 0 10px;
  font-size: 1.15rem;
  color: var(--blue-deep);
}

.prose p,
.prose li {
  color: #2b3745;
}

.prose p {
  margin: 0 0 14px;
  text-align: justify;
}

.prose ul,
.prose ol {
  margin: 0 0 16px;
  padding-left: 1.2em;
}

.prose li {
  margin-bottom: 8px;
}

.toc {
  background: linear-gradient(180deg, #f7fbff, #eef6ff);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px 20px;
  margin: 0 0 24px;
}

.toc strong {
  display: block;
  margin-bottom: 10px;
  color: var(--blue-deep);
}

.toc ol {
  margin: 0;
  padding-left: 1.2em;
  columns: 2;
  column-gap: 24px;
}

.toc li {
  break-inside: avoid;
  margin-bottom: 6px;
}

.figure {
  margin: 18px 0 22px;
  text-align: center;
}

.figure img {
  margin: 0 auto;
  border-radius: 16px;
  border: 1px solid var(--line);
  box-shadow: 0 8px 28px rgba(26, 95, 173, 0.1);
  max-width: min(100%, 420px);
}

.figure.wide img {
  max-width: min(100%, 720px);
}

.figure figcaption {
  margin-top: 10px;
  color: var(--muted);
  font-size: 0.92rem;
}

.grid-2 {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 18px;
  margin: 18px 0 22px;
}

.grid-2 .figure {
  margin: 0;
}

.grid-2 img {
  max-width: 100%;
}

.callout {
  background: var(--blue-soft);
  border-left: 4px solid var(--blue);
  border-radius: 0 12px 12px 0;
  padding: 14px 16px;
  margin: 0 0 18px;
  color: #23425f;
}

.related {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 14px;
  margin: 8px 0 24px;
}

.related a {
  display: block;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 16px;
  text-decoration: none;
  color: var(--ink);
  box-shadow: var(--shadow);
  transition: transform 0.2s ease, border-color 0.2s ease;
}

.related a:hover {
  transform: translateY(-2px);
  border-color: #9ec5ea;
  text-decoration: none;
}

.related strong {
  display: block;
  color: var(--blue-deep);
  margin-bottom: 6px;
}

.related span {
  color: var(--muted);
  font-size: 0.92rem;
}

.page-hero {
  padding: 36px 0 10px;
}

.page-hero h1 {
  margin: 0 0 10px;
  font-size: clamp(1.6rem, 3vw, 2.2rem);
  font-family: var(--display);
}

.page-hero p {
  margin: 0;
  color: var(--muted);
  max-width: 46em;
}

.site-footer {
  margin-top: 40px;
  padding: 28px 0 36px;
  border-top: 1px solid var(--line);
  background: rgba(255, 255, 255, 0.72);
}

.footer-grid {
  display: grid;
  grid-template-columns: 1.4fr 1fr 1fr;
  gap: 24px;
}

.footer-brand {
  display: flex;
  gap: 12px;
  align-items: flex-start;
}

.footer-brand img {
  width: 48px;
  height: 48px;
  border-radius: 12px;
}

.footer-brand strong {
  display: block;
  margin-bottom: 4px;
}

.footer-brand p,
.site-footer p {
  margin: 0;
  color: var(--muted);
  font-size: 0.92rem;
}

.footer-links h3 {
  margin: 0 0 10px;
  font-size: 0.95rem;
}

.footer-links a {
  display: block;
  margin-bottom: 8px;
  color: var(--muted);
  font-size: 0.92rem;
}

.copyright {
  margin-top: 22px;
  padding-top: 16px;
  border-top: 1px solid var(--line);
  text-align: center;
  color: var(--muted);
  font-size: 0.88rem;
}

.error-wrap {
  min-height: 70vh;
  display: grid;
  place-items: center;
  text-align: center;
  padding: 48px 16px;
}

.error-wrap h1 {
  margin: 0 0 8px;
  font-size: clamp(2.4rem, 8vw, 4rem);
  color: var(--blue-deep);
}

.error-wrap p {
  margin: 0 0 20px;
  color: var(--muted);
}

.breadcrumb {
  margin: 0 0 18px;
  color: var(--muted);
  font-size: 0.9rem;
}

.breadcrumb a {
  color: var(--muted);
}

@media (max-width: 900px) {
  .hero-grid,
  .footer-grid,
  .related,
  .grid-2 {
    grid-template-columns: 1fr;
  }

  .toc ol {
    columns: 1;
  }

  .header-inner {
    flex-direction: column;
    align-items: flex-start;
  }

  .nav {
    justify-content: flex-start;
  }

  .prose {
    padding: 20px 16px 6px;
  }

  .hero {
    padding-top: 28px;
  }

  .hero-visual img,
  .figure img {
    max-width: min(100%, 320px);
  }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  .btn,
  .related a {
    transition: none;
  }
}