:root {
  --page: #f6f8f6;
  --surface: #ffffff;
  --surface-soft: #fbfcfb;
  --ink: #18211d;
  --body: #526059;
  --muted: #7b8781;
  --line: #dfe6e1;
  --line-strong: #cbd6cf;
  --accent: #176b54;
  --accent-strong: #0f5744;
  --accent-soft: #eaf4ef;
  --blue: #315f7d;
  --serif: "Songti SC", STSong, "Noto Serif CJK SC", serif;
  --sans: -apple-system, BlinkMacSystemFont, "PingFang SC", "Microsoft YaHei", "Noto Sans SC", "Helvetica Neue", sans-serif;
  --mono: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
  --max: 1080px;
  color: var(--ink);
  background: var(--page);
}

html {
  scroll-behavior: smooth;
  background: var(--page);
}

body {
  margin: 0;
  min-height: 100vh;
  overflow-x: hidden;
  background: var(--surface);
  color: var(--ink);
  font-family: var(--sans);
  text-rendering: optimizeLegibility;
}

[hidden] {
  display: none !important;
}

.site-shell {
  width: min(var(--max), calc(100vw - 48px));
  margin-inline: auto;
}

.reading-progress {
  position: fixed;
  top: 0;
  left: 0;
  z-index: 50;
  width: 100%;
  height: 3px;
  transform: scaleX(0);
  transform-origin: left center;
  background: var(--accent);
  pointer-events: none;
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 30;
  border-bottom: 1px solid rgba(223, 230, 225, 0.92);
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(16px);
}

.nav {
  min-height: 64px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-direction: row;
  gap: 20px;
  padding: 0;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  color: var(--ink);
  text-decoration: none;
}

.brand-mark {
  width: 34px;
  height: 34px;
  border-radius: 8px;
}

.brand .brand-copy {
  display: grid;
  gap: 2px;
  color: var(--ink);
  font-family: var(--sans);
  font-size: inherit;
  letter-spacing: 0;
  text-transform: none;
}

.brand strong {
  font-size: 17px;
  line-height: 1.05;
}

.brand .brand-copy > span,
.article-kicker,
.tag,
.back-link {
  color: var(--muted);
  font-family: var(--mono);
  font-size: 10px;
  letter-spacing: 0.05em;
  line-height: 1.2;
  text-transform: uppercase;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 4px;
  flex-wrap: nowrap;
  color: var(--body);
  font-size: 14px;
}

.nav-links a {
  min-height: 40px;
  display: inline-flex;
  align-items: center;
  padding: 0 12px;
  border: 0;
  border-radius: 6px;
  background: transparent;
  text-decoration: none;
}

.nav-links a:hover,
.nav-links a:focus-visible {
  background: var(--accent-soft);
  color: var(--accent-strong);
  outline: none;
}

main.site-shell {
  padding: 72px 0 88px;
}

.article-hero {
  padding-bottom: 34px;
  border-bottom: 1px solid var(--line-strong);
}

.article-kicker {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 18px;
}

.article-hero h1 {
  max-width: 900px;
  margin: 0;
  color: var(--ink);
  font-family: var(--serif);
  font-size: 52px;
  font-weight: 700;
  line-height: 1.12;
  letter-spacing: 0;
  text-wrap: balance;
}

.article-summary {
  max-width: 760px;
  margin: 22px 0 0;
  color: var(--body);
  font-size: 18px;
  line-height: 1.78;
  text-wrap: pretty;
}

.tags {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 22px;
}

.tag {
  padding: 7px 10px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--surface);
  color: var(--body);
  text-transform: none;
}

.mobile-toc {
  display: none;
}

.article-layout {
  display: grid;
  grid-template-columns: minmax(0, 760px) minmax(180px, 1fr);
  gap: 70px;
  align-items: start;
  min-width: 0;
}

.article-main-column {
  min-width: 0;
}

.article-content {
  max-width: 760px;
  min-width: 0;
  margin-top: 40px;
  color: var(--body);
  font-size: 17px;
  line-height: 1.86;
}

.article-content h2,
.article-content h3 {
  scroll-margin-top: 88px;
  color: var(--ink);
  font-family: var(--serif);
  letter-spacing: 0;
  text-wrap: balance;
}

.article-content h2 {
  margin: 52px 0 16px;
  font-size: 29px;
  line-height: 1.34;
}

.article-content h3 {
  margin: 36px 0 12px;
  font-size: 22px;
  line-height: 1.4;
}

.article-content p {
  margin: 0 0 19px;
  text-wrap: pretty;
}

.article-content strong {
  color: var(--ink);
  font-weight: 720;
}

.article-content a {
  color: var(--accent-strong);
  text-decoration-thickness: 1px;
  text-underline-offset: 4px;
}

.article-content blockquote {
  margin: 28px 0;
  padding: 18px 20px;
  border: 1px solid #cde0d7;
  border-left: 1px solid #cde0d7;
  border-radius: 8px;
  background: var(--accent-soft);
  color: var(--ink);
}

.article-content blockquote p:last-child {
  margin-bottom: 0;
}

.article-content ul,
.article-content ol {
  margin: 0 0 22px;
  padding-left: 1.35em;
}

.article-content li {
  margin: 9px 0;
  padding-left: 0.15em;
}

.article-content figure {
  margin: 30px 0 34px;
}

.article-content img {
  display: block;
  width: 100%;
  height: auto;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
}

.article-content figcaption {
  margin-top: 9px;
  color: var(--muted);
  font-size: 13px;
  line-height: 1.55;
  text-align: center;
}

.article-content code,
.article-content pre {
  font-family: var(--mono);
}

.article-content code {
  padding: 0.12em 0.3em;
  border: 1px solid var(--line);
  border-radius: 4px;
  background: var(--surface-soft);
  color: var(--ink);
  font-size: 0.92em;
}

.article-content pre {
  max-width: 100%;
  margin: 0;
  overflow-x: auto;
  white-space: pre;
}

.diagram {
  max-width: 100%;
  margin: 30px 0 34px;
  padding: 18px;
  overflow-x: auto;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface-soft);
  overscroll-behavior-x: contain;
}

.diagram pre {
  padding: 0;
  color: var(--body);
  font-size: 13px;
  line-height: 1.55;
}

.diagram-fallback-note {
  margin: 0 0 12px;
  color: var(--accent-strong);
  font-size: 13px;
  font-weight: 650;
  line-height: 1.6;
}

.diagram svg {
  display: block;
  max-width: 100%;
  height: auto;
  margin: 0 auto;
}

.article-toc {
  position: sticky;
  top: 94px;
  margin-top: 40px;
  padding-left: 20px;
  border-left: 1px solid var(--line);
}

.article-toc strong {
  color: var(--ink);
  font-size: 13px;
}

.article-toc ol,
.mobile-toc ol {
  display: grid;
  gap: 10px;
  margin: 14px 0 0;
  padding: 0;
  list-style: none;
}

.article-toc a,
.mobile-toc a {
  color: var(--muted);
  font-size: 12px;
  line-height: 1.55;
  text-decoration: none;
}

.article-toc a:hover,
.article-toc a:focus-visible,
.mobile-toc a:hover,
.mobile-toc a:focus-visible {
  color: var(--accent-strong);
  outline: none;
}

.article-author {
  display: grid;
  grid-template-columns: 48px minmax(0, 1fr) auto;
  gap: 14px;
  align-items: center;
  margin-top: 52px;
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--accent-soft);
}

.article-author img {
  width: 48px;
  height: 48px;
  border-radius: 10px;
}

.article-author strong {
  display: block;
  color: var(--ink);
  font-size: 15px;
}

.article-author p {
  margin: 4px 0 0;
  color: var(--body);
  font-size: 13px;
  line-height: 1.6;
}

.article-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.article-action,
.back-link {
  min-height: 42px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0 13px;
  border: 1px solid var(--line-strong);
  border-radius: 7px;
  background: var(--surface);
  color: var(--body);
  font-family: var(--sans);
  font-size: 13px;
  letter-spacing: 0;
  text-decoration: none;
  text-transform: none;
  cursor: pointer;
}

.article-action:hover,
.article-action:focus-visible,
.back-link:hover,
.back-link:focus-visible {
  border-color: var(--accent);
  color: var(--accent-strong);
  outline: none;
}

.article-footer {
  display: flex;
  justify-content: space-between;
  gap: 18px;
  margin-top: 28px;
  padding-top: 20px;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: 12px;
}

.article-legal {
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-end;
  gap: 8px 14px;
}

.article-legal a {
  color: inherit;
  text-decoration: none;
}

.article-legal a:hover,
.article-legal a:focus-visible {
  color: var(--accent-strong);
  outline: none;
}

.related-articles {
  margin-top: 58px;
  padding-top: 34px;
  border-top: 1px solid var(--line-strong);
}

.related-articles h2 {
  margin: 0;
  color: var(--ink);
  font-family: var(--serif);
  font-size: 28px;
}

.related-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
  margin-top: 18px;
}

.related-card {
  display: block;
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface-soft);
  color: var(--ink);
  text-decoration: none;
}

.related-card span {
  color: var(--muted);
  font-family: var(--mono);
  font-size: 10px;
}

.related-card strong {
  display: block;
  margin-top: 8px;
  font-size: 15px;
  line-height: 1.55;
  text-wrap: pretty;
}

.related-card:hover,
.related-card:focus-visible {
  border-color: var(--accent);
  color: var(--accent-strong);
  outline: none;
}

:focus-visible {
  outline: 2px solid rgba(23, 107, 84, 0.42);
  outline-offset: 3px;
}

@media (max-width: 900px) {
  .article-layout {
    grid-template-columns: 1fr;
    gap: 0;
  }

  .article-toc {
    display: none;
  }

  .mobile-toc {
    display: block;
    margin-top: 24px;
    padding: 14px 16px;
    border: 1px solid var(--line);
    border-radius: 8px;
    background: var(--surface-soft);
  }

  .mobile-toc summary {
    min-height: 44px;
    display: flex;
    align-items: center;
    color: var(--ink);
    font-size: 14px;
    font-weight: 650;
    cursor: pointer;
  }

  .mobile-toc a {
    min-height: 44px;
    display: flex;
    align-items: center;
    font-size: 13px;
  }
}

@media (max-width: 720px) {
  .site-shell {
    width: min(100% - 28px, var(--max));
  }

  .nav {
    min-height: 56px;
    flex-direction: row;
    align-items: center;
    gap: 10px;
    padding: 0;
  }

  .brand-mark {
    width: 30px;
    height: 30px;
  }

  .brand-copy span {
    display: none;
  }

  .brand .brand-copy {
    display: grid;
  }

  .brand strong {
    font-size: 15px;
  }

  .nav-links {
    gap: 0;
    font-size: 13px;
  }

  .nav-links a {
    min-width: 44px;
    min-height: 44px;
    padding-inline: 8px;
  }

  main.site-shell {
    padding: 40px 0 64px;
  }

  .article-hero {
    padding-bottom: 28px;
  }

  .article-kicker {
    gap: 8px;
    margin-bottom: 14px;
  }

  .article-hero h1 {
    font-size: 34px;
    line-height: 1.16;
  }

  .article-summary {
    margin-top: 18px;
    font-size: 16px;
    line-height: 1.76;
  }

  .tags {
    margin-top: 18px;
  }

  .tag {
    padding: 6px 9px;
  }

  .article-content {
    margin-top: 30px;
    font-size: 17px;
    line-height: 1.82;
  }

  .article-content h2 {
    margin-top: 44px;
    font-size: 25px;
    line-height: 1.38;
  }

  .article-content h3 {
    font-size: 21px;
  }

  .article-content p {
    margin-bottom: 18px;
  }

  .diagram {
    margin-inline: -14px;
    padding: 16px 14px 18px;
    border-right: 0;
    border-left: 0;
    border-radius: 0;
  }

  .diagram .mermaid {
    min-width: 620px;
  }

  .diagram svg {
    max-width: none;
    min-width: 620px;
  }

  .article-author {
    grid-template-columns: 44px minmax(0, 1fr);
  }

  .article-author img {
    width: 44px;
    height: 44px;
  }

  .article-actions {
    grid-column: 1 / -1;
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .article-action,
  .back-link {
    min-height: 44px;
  }

  .article-footer {
    align-items: flex-start;
    flex-direction: column;
  }

  .article-legal {
    justify-content: flex-start;
  }

  .related-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 380px) {
  .brand-mark {
    display: none;
  }

  .nav-links a {
    padding-inline: 6px;
  }

  .article-hero h1 {
    font-size: 31px;
  }
}

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

  *,
  *::before,
  *::after {
    scroll-behavior: auto !important;
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
  }
}