:root {
  color-scheme: light;
  --canvas: #f7f9fc;
  --paper: #ffffff;
  --ink: #3a4856;
  --ink-strong: #243746;
  --heading-primary: #2d6380;
  --heading-secondary: #294d63;
  --muted: #71808d;
  --faint: #98a4b1;
  --line: #dfe6ed;
  --line-soft: #edf1f5;
  --accent: #24658a;
  --accent-deep: #174866;
  --accent-soft: #e8f3f8;
  --code-bg: #0d1721;
  --code-surface: #152331;
  --code-text: #d9e5ef;
  --code-muted: #8fa3b5;
  --warning-bg: #fff8e8;
  --warning-line: #d69b2d;
  --header-height: 4.5rem;
  --sidebar-width: 19.5rem;
  --toc-width: 13rem;
  --content-width: 48rem;
  --shadow-soft: 0 18px 60px rgb(28 48 68 / 8%);
  font-family:
    Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont,
    "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei",
    sans-serif;
  font-synthesis: none;
  text-rendering: optimizeLegibility;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--header-height) + 1.5rem);
}

body {
  margin: 0;
  min-width: 20rem;
  color: var(--ink);
  background:
    linear-gradient(90deg, rgb(36 101 138 / 3%) 1px, transparent 1px) 0 0 /
      4rem 4rem,
    var(--canvas);
}

button,
a {
  -webkit-tap-highlight-color: transparent;
}

a {
  color: inherit;
}

.reading-progress {
  position: fixed;
  inset: 0 0 auto;
  z-index: 100;
  height: 0.1875rem;
  background: transparent;
}

.reading-progress__bar {
  width: 0;
  height: 100%;
  background: linear-gradient(90deg, #3388ad, #174866);
  transition: width 100ms linear;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 40;
  display: grid;
  grid-template-columns: var(--sidebar-width) minmax(0, 1fr) var(--toc-width);
  align-items: center;
  min-height: var(--header-height);
  padding: 0 clamp(1rem, 2.6vw, 2.25rem);
  border-bottom: 1px solid rgb(201 213 224 / 82%);
  background: rgb(250 252 254 / 92%);
  backdrop-filter: blur(18px) saturate(150%);
}

.brand {
  display: inline-flex;
  grid-column: 1 / 3;
  align-items: center;
  justify-self: start;
  gap: 0.75rem;
  text-decoration: none;
}

.brand__mark {
  display: grid;
  width: 2.25rem;
  height: 2.25rem;
  place-items: center;
  border: 1px solid var(--accent);
  border-radius: 0.35rem 0.85rem 0.35rem 0.35rem;
  color: #fff;
  background: var(--accent-deep);
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  font-size: 0.75rem;
  font-weight: 800;
  letter-spacing: 0.05em;
  box-shadow: 0 0.35rem 1.1rem rgb(23 72 102 / 18%);
}

.brand__text {
  display: flex;
  flex-direction: column;
  gap: 0.08rem;
  line-height: 1.2;
}

.brand__text strong {
  color: var(--ink-strong);
  font-family:
    Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont,
    "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei",
    sans-serif;
  font-size: 1.02rem;
  font-weight: 700;
  letter-spacing: 0.015em;
}

.brand__text small {
  color: var(--muted);
  font-size: 0.72rem;
  letter-spacing: 0.12em;
}

.github-link {
  display: inline-flex;
  grid-column: 3;
  align-items: center;
  justify-self: end;
  gap: 0.3rem;
  color: var(--accent-deep);
  font-size: 0.875rem;
  font-weight: 700;
  text-decoration: none;
}

.github-link:hover {
  color: var(--accent);
}

.icon-button {
  display: none;
  border: 0;
  background: transparent;
}

.page-shell {
  display: grid;
  grid-template-columns: var(--sidebar-width) minmax(0, 1fr) var(--toc-width);
  align-items: start;
  max-width: 96rem;
  min-height: calc(100vh - var(--header-height));
  margin: 0 auto;
  padding: 0 clamp(1rem, 2.6vw, 2.25rem);
}

.book-sidebar,
.page-toc {
  position: sticky;
  top: var(--header-height);
  max-height: calc(100vh - var(--header-height));
  overflow: auto;
  scrollbar-width: thin;
  scrollbar-color: #cbd6df transparent;
}

.book-sidebar {
  padding: 2.15rem 2rem 3rem 0;
  border-right: 1px solid var(--line);
}

.sidebar__heading {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin: 0 0 1.2rem;
  color: var(--muted);
  font-size: 0.75rem;
  font-weight: 800;
  letter-spacing: 0.12em;
}

.sidebar__heading span:last-child {
  color: var(--faint);
  font-weight: 600;
  letter-spacing: 0.03em;
}

.nav-section + .nav-section {
  margin-top: 1.55rem;
}

.nav-section__title {
  margin: 0 0 0.55rem;
  color: var(--accent-deep);
  font-size: 0.72rem;
  font-weight: 800;
  letter-spacing: 0.08em;
}

.nav-section__list {
  display: grid;
  gap: 0.13rem;
  margin: 0;
  padding: 0;
  list-style: none;
}

.nav-link {
  position: relative;
  display: block;
  width: 100%;
  padding: 0.48rem 0.65rem 0.48rem 0.8rem;
  border: 0;
  border-radius: 0.4rem;
  color: #586777;
  background: transparent;
  font: inherit;
  font-size: 0.82rem;
  line-height: 1.55;
  text-align: left;
  cursor: pointer;
}

.nav-link::before {
  position: absolute;
  top: 0.72rem;
  bottom: 0.72rem;
  left: 0;
  width: 0.14rem;
  border-radius: 1rem;
  background: transparent;
  content: "";
}

.nav-link:hover {
  color: var(--ink-strong);
  background: #eef3f7;
}

.nav-link.is-active {
  color: var(--accent-deep);
  background: var(--accent-soft);
  font-weight: 700;
}

.nav-link.is-active::before {
  background: var(--accent);
}

.nav-skeleton {
  display: grid;
  gap: 0.75rem;
}

.nav-skeleton span,
.loading-line {
  display: block;
  height: 0.8rem;
  border-radius: 2rem;
  background: linear-gradient(90deg, #e8edf2, #f5f7f9, #e8edf2) 0 0 / 200%
    100%;
  animation: shimmer 1.35s infinite linear;
}

.nav-skeleton span:nth-child(2),
.nav-skeleton span:nth-child(5) {
  width: 82%;
}

.nav-skeleton span:nth-child(3) {
  width: 91%;
}

.reader {
  width: 100%;
  max-width: calc(var(--content-width) + 7rem);
  min-height: calc(100vh - var(--header-height));
  margin: 0 auto;
  padding: 3.7rem 3.5rem 5rem;
  outline: none;
}

.article-meta {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  max-width: var(--content-width);
  margin: 0 auto 1.2rem;
  color: var(--accent);
  font-size: 0.72rem;
  font-weight: 800;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.article-meta__rule {
  width: 2rem;
  height: 1px;
  background: #a9c4d3;
}

.markdown-body {
  max-width: var(--content-width);
  margin: 0 auto;
  color: var(--ink);
  font-family:
    Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont,
    "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei",
    sans-serif;
  font-size: 1.04rem;
  line-height: 1.9;
  overflow-wrap: anywhere;
}

.markdown-body h1,
.markdown-body h2,
.markdown-body h3,
.markdown-body h4 {
  color: var(--ink-strong);
  font-family:
    Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont,
    "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei",
    sans-serif;
  font-weight: 700;
  line-height: 1.38;
  text-wrap: balance;
}

.markdown-body h1 {
  margin: 0 0 2.2rem;
  color: var(--heading-primary);
  font-size: clamp(1.95rem, 4vw, 2.8rem);
  letter-spacing: -0.022em;
}

.markdown-body h1::after {
  display: block;
  width: 3.4rem;
  height: 0.2rem;
  margin-top: 1.25rem;
  border-radius: 1rem;
  background: var(--accent);
  content: "";
}

.markdown-body h2 {
  margin: 4rem 0 1.35rem;
  padding-top: 0.2rem;
  color: var(--heading-secondary);
  font-size: clamp(1.55rem, 2.6vw, 2.05rem);
  letter-spacing: -0.018em;
}

.markdown-body h3 {
  margin: 2.5rem 0 0.8rem;
  color: #34566a;
  font-size: 1.22rem;
}

.markdown-body h4 {
  margin: 2rem 0 0.6rem;
  font-size: 1.05rem;
}

.heading-anchor {
  color: inherit;
  text-decoration: none;
}

.heading-anchor::after {
  margin-left: 0.4rem;
  color: transparent;
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: 0.72em;
  content: "#";
  transition: color 120ms ease;
}

.markdown-body h2:hover .heading-anchor::after,
.markdown-body h3:hover .heading-anchor::after,
.heading-anchor:focus-visible::after {
  color: #9bb2c1;
}

.markdown-body p {
  margin: 1.15rem 0;
}

.markdown-body strong {
  color: var(--ink-strong);
  font-weight: 750;
}

.markdown-body a {
  color: var(--accent-deep);
  text-decoration-color: #93b8ca;
  text-decoration-thickness: 0.08em;
  text-underline-offset: 0.2em;
}

.markdown-body a:hover {
  color: #0d719d;
  text-decoration-color: currentColor;
}

.markdown-body ul,
.markdown-body ol {
  margin: 1.2rem 0;
  padding-left: 1.5rem;
}

.markdown-body li {
  margin: 0.45rem 0;
  padding-left: 0.18rem;
}

.markdown-body li::marker {
  color: var(--accent);
  font-weight: 700;
}

.markdown-body blockquote {
  margin: 1.7rem 0;
  padding: 0.8rem 1.2rem;
  border-left: 0.22rem solid var(--accent);
  color: #425466;
  background: #edf6fa;
}

.markdown-body blockquote > :first-child {
  margin-top: 0;
}

.markdown-body blockquote > :last-child {
  margin-bottom: 0;
}

.markdown-body :not(pre) > code {
  padding: 0.16em 0.38em;
  border: 1px solid #d8e2e9;
  border-radius: 0.28rem;
  color: #155475;
  background: #eef4f7;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas,
    "Liberation Mono", monospace;
  font-size: 0.88em;
}

.markdown-body pre {
  position: relative;
  margin: 1.75rem 0;
  padding: 2.65rem 1.25rem 1.25rem;
  overflow: auto;
  border: 1px solid #263747;
  border-radius: 0.7rem;
  color: var(--code-text);
  background: var(--code-bg);
  box-shadow: 0 1rem 2.4rem rgb(13 23 33 / 14%);
  scrollbar-color: #3a5267 var(--code-bg);
}

.markdown-body pre::before {
  position: absolute;
  top: 1.05rem;
  left: 1.25rem;
  width: 0.5rem;
  height: 0.5rem;
  border-radius: 50%;
  background: #ff6b67;
  box-shadow: 0.85rem 0 #f4c04f, 1.7rem 0 #4ecb71;
  content: "";
}

.markdown-body pre code {
  display: block;
  min-width: max-content;
  padding: 0;
  color: inherit;
  background: transparent;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas,
    "Liberation Mono", monospace;
  font-size: 0.88rem;
  line-height: 1.7;
  tab-size: 4;
}

.code-language {
  position: absolute;
  top: 0.65rem;
  right: 3.5rem;
  color: var(--code-muted);
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.copy-code {
  position: absolute;
  top: 0.48rem;
  right: 0.55rem;
  min-width: 2.35rem;
  padding: 0.26rem 0.45rem;
  border: 1px solid #344a5d;
  border-radius: 0.32rem;
  color: #afc0ce;
  background: var(--code-surface);
  font: 600 0.68rem/1.2 ui-sans-serif, system-ui, sans-serif;
  cursor: pointer;
}

.copy-code:hover,
.copy-code:focus-visible {
  color: #fff;
  border-color: #557088;
}

.markdown-body table {
  width: 100%;
  margin: 1.75rem 0;
  border-collapse: collapse;
  font-family: ui-sans-serif, system-ui, "PingFang SC", sans-serif;
  font-size: 0.9rem;
  line-height: 1.65;
}

.markdown-body th,
.markdown-body td {
  padding: 0.72rem 0.8rem;
  border: 1px solid var(--line);
  text-align: left;
  vertical-align: top;
}

.markdown-body th {
  color: var(--ink-strong);
  background: #edf3f7;
  font-weight: 750;
}

.markdown-body tbody tr:nth-child(even) {
  background: #fafcfd;
}

.markdown-body hr {
  height: 1px;
  margin: 3rem 0;
  border: 0;
  background: var(--line);
}

.article-loading {
  display: grid;
  gap: 1rem;
  padding-top: 1rem;
}

.loading-line {
  height: 1rem;
}

.loading-line--short {
  width: 48%;
  height: 2.8rem;
  margin-bottom: 1.6rem;
}

.loading-line--medium {
  width: 72%;
}

.article-error {
  padding: 2rem;
  border: 1px solid #e3c37f;
  border-radius: 0.65rem;
  background: var(--warning-bg);
  font-family: ui-sans-serif, system-ui, sans-serif;
}

.article-error h1 {
  margin: 0 0 0.8rem;
  font-size: 1.4rem;
}

.article-error h1::after {
  display: none;
}

.chapter-pager {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1rem;
  max-width: var(--content-width);
  margin: 4rem auto 0;
  padding-top: 1.5rem;
  border-top: 1px solid var(--line);
}

.pager-link {
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
  min-height: 5rem;
  padding: 0.9rem 1rem;
  border: 1px solid var(--line);
  border-radius: 0.55rem;
  color: var(--ink);
  background: var(--paper);
  text-decoration: none;
  box-shadow: 0 0.4rem 1.3rem rgb(34 59 79 / 4%);
}

.pager-link:last-child {
  text-align: right;
}

.pager-link:hover {
  border-color: #a9c3d2;
  box-shadow: 0 0.6rem 1.8rem rgb(34 59 79 / 8%);
}

.pager-link small {
  color: var(--muted);
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.06em;
}

.pager-link strong {
  font-size: 0.86rem;
  line-height: 1.45;
}

.page-toc {
  padding: 2.2rem 0 3rem 1.5rem;
}

.page-toc__title {
  margin-bottom: 0.8rem;
  color: var(--muted);
  font-size: 0.72rem;
  font-weight: 800;
  letter-spacing: 0.1em;
}

#page-toc {
  display: grid;
  gap: 0.15rem;
  border-left: 1px solid var(--line);
}

.toc-link {
  display: block;
  margin-left: -1px;
  padding: 0.35rem 0 0.35rem 0.85rem;
  border-left: 1px solid transparent;
  color: #7b8895;
  font-size: 0.75rem;
  line-height: 1.45;
  text-decoration: none;
}

.toc-link--h3 {
  padding-left: 1.5rem;
  font-size: 0.72rem;
}

.toc-link:hover,
.toc-link.is-active {
  border-left-color: var(--accent);
  color: var(--accent-deep);
}

.sidebar-scrim {
  display: none;
}

.noscript-message {
  max-width: 42rem;
  margin: 3rem auto;
  padding: 1rem;
  border: 1px solid #e3c37f;
  border-radius: 0.5rem;
  background: var(--warning-bg);
}

@keyframes shimmer {
  to {
    background-position: -200% 0;
  }
}

@media (max-width: 74rem) {
  :root {
    --sidebar-width: 17.5rem;
  }

  .site-header,
  .page-shell {
    grid-template-columns: var(--sidebar-width) minmax(0, 1fr);
  }

  .github-link {
    grid-column: 2;
  }

  .brand {
    grid-column: 1;
  }

  .page-toc {
    display: none;
  }
}

@media (max-width: 52rem) {
  :root {
    --header-height: 4rem;
  }

  .site-header {
    grid-template-columns: 2.7rem minmax(0, 1fr) auto;
    padding: 0 1rem;
  }

  .menu-button {
    display: grid;
    grid-column: 1;
    width: 2.4rem;
    height: 2.4rem;
    place-content: center;
    gap: 0.25rem;
    border-radius: 0.4rem;
    cursor: pointer;
  }

  .menu-button span {
    display: block;
    width: 1.1rem;
    height: 0.1rem;
    border-radius: 1rem;
    background: var(--ink);
  }

  .menu-button:hover {
    background: #edf2f6;
  }

  .brand {
    grid-column: 2;
  }

  .brand__mark,
  .brand__text small {
    display: none;
  }

  .brand__text strong {
    font-size: 0.92rem;
  }

  .github-link {
    grid-column: 3;
    font-size: 0.8rem;
  }

  .page-shell {
    display: block;
    padding: 0;
  }

  .book-sidebar {
    position: fixed;
    z-index: 60;
    top: 0;
    bottom: 0;
    left: 0;
    width: min(86vw, 21rem);
    max-height: none;
    padding: 1.5rem 1rem 3rem;
    border-right: 1px solid var(--line);
    background: #f9fbfd;
    box-shadow: var(--shadow-soft);
    transform: translateX(-105%);
    transition: transform 180ms ease;
  }

  .book-sidebar.is-open {
    transform: translateX(0);
  }

  .sidebar-scrim {
    position: fixed;
    z-index: 50;
    inset: 0;
    width: 100%;
    height: 100%;
    border: 0;
    background: rgb(13 23 33 / 36%);
    opacity: 0;
    pointer-events: none;
    transition: opacity 180ms ease;
  }

  .sidebar-scrim.is-visible {
    display: block;
    opacity: 1;
    pointer-events: auto;
  }

  .reader {
    max-width: none;
    padding: 2.6rem 1.25rem 4rem;
  }

  .markdown-body {
    font-size: 1rem;
    line-height: 1.88;
  }

  .markdown-body h1 {
    font-size: clamp(1.85rem, 8vw, 2.45rem);
  }

  .markdown-body h2 {
    margin-top: 3.25rem;
  }

  .markdown-body pre {
    margin-right: -0.35rem;
    margin-left: -0.35rem;
    border-radius: 0.55rem;
  }

  .markdown-body table {
    display: block;
    overflow-x: auto;
    white-space: nowrap;
  }

  .chapter-pager {
    grid-template-columns: 1fr;
  }

  .pager-link:last-child {
    text-align: left;
  }
}

@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;
  }
}

@media print {
  body {
    background: #fff;
  }

  .site-header,
  .book-sidebar,
  .page-toc,
  .reading-progress,
  .chapter-pager,
  .copy-code,
  .article-meta {
    display: none !important;
  }

  .page-shell {
    display: block;
  }

  .reader {
    max-width: none;
    padding: 0;
  }

  .markdown-body {
    max-width: none;
  }

  .markdown-body pre {
    white-space: pre-wrap;
    box-shadow: none;
  }
}