* {
  box-sizing: border-box;
}
:root {
  color-scheme: light;
  font-family:
    -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', sans-serif;
  font-size: 100%;
  font-optical-sizing: auto;
  color: #1d1d1f;
  background: #fff;
  --ink: #1d1d1f;
  --body: #45454b;
  --muted: #68686d;
  --subtle: #6e6e73;
  --line: #e8e8ed;
  --soft: #f5f5f7;
  --accent: #0066cc;
  --focus: #0071e3;
  --page-max: 72rem;
  --page-pad: 2.5rem;
  --content-gap: 5rem;
  --section-gap: 3rem;
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-10: 2.5rem;
  --space-14: 3.5rem;
  --radius-pill: 2rem;
}
body {
  margin: 0;
}
a {
  color: var(--accent);
  text-underline-offset: 0.22em;
}
a:hover {
  text-decoration: underline;
}
a:active {
  opacity: 0.65;
}
a:focus-visible,
summary:focus-visible {
  outline: 3px solid var(--focus);
  outline-offset: 5px;
  border-radius: 4px;
}
.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  background: rgb(255 255 255 / 90%);
  backdrop-filter: saturate(160%) blur(20px);
}
.header-inner {
  max-width: var(--page-max);
  min-height: 5rem;
  margin-inline: auto;
  padding: 1rem var(--page-pad);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-6);
}
.brand {
  display: flex;
  align-items: center;
  flex-shrink: 0;
}
.brand-logo {
  display: block;
  width: auto;
  height: 2rem;
}
.page-nav {
  display: flex;
  gap: var(--space-1);
  padding: var(--space-1);
  border-radius: var(--radius-pill);
  background: var(--soft);
}
.page-nav a {
  min-height: 2.25rem;
  display: grid;
  place-items: center;
  padding: 0.5rem 1rem;
  color: #55555b;
  font-size: 0.8125rem;
  line-height: 1.3;
  text-decoration: none;
  border-radius: var(--radius-pill);
}
.page-nav a[aria-current='page'] {
  color: #1d1d1f;
  background: #fff;
  box-shadow: 0 1px 4px rgb(0 0 0 / 8%);
  font-weight: 600;
}
.layout {
  max-width: var(--page-max);
  margin-inline: auto;
  padding: 4.5rem var(--page-pad) 6rem;
  display: grid;
  grid-template-columns: 13rem minmax(0, 1fr);
  column-gap: var(--content-gap);
  align-items: start;
}
.document-heading {
  grid-column: 2;
  padding-bottom: 2.5rem;
  border-bottom: 1px solid var(--line);
  margin-bottom: var(--section-gap);
}
.eyebrow {
  margin: 0 0 1rem;
  color: var(--muted);
  font-size: 0.8125rem;
  font-weight: 500;
  letter-spacing: 0.04em;
}
h1 {
  margin: 0;
  font-size: clamp(2rem, 4vw, 2.5rem);
  line-height: 1.15;
  font-weight: 600;
  letter-spacing: -0.035em;
  text-indent: -2px;
}
.introduction {
  margin: 1.25rem 0 1.75rem;
  color: var(--subtle);
  font-size: 1.0625rem;
  line-height: 1.8;
  max-width: 34rem;
}
.meta {
  margin: 0;
  color: var(--muted);
  font-size: 0.75rem;
  line-height: 1.8;
}
.meta time {
  margin-left: 0.75rem;
}
.sidebar {
  grid-column: 1;
  grid-row: 2;
  position: sticky;
  top: 7rem;
}
.contents summary {
  color: var(--ink);
  font-size: 0.8125rem;
  font-weight: 600;
  line-height: 1.5;
  cursor: pointer;
  list-style: none;
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: 2.75rem;
}
.contents summary::-webkit-details-marker {
  display: none;
}
.contents summary span {
  color: var(--muted);
  margin-right: 0.5rem;
}
.contents[open] summary span {
  transform: rotate(180deg);
}
.contents ol {
  list-style: none;
  padding: 0.5rem 0 0;
  margin: 0;
  counter-reset: chapter;
}
.contents li {
  counter-increment: chapter;
}
.contents a {
  display: flex;
  align-items: baseline;
  gap: 0.75rem;
  padding: 0.65rem 0;
  color: var(--muted);
  font-size: 0.8125rem;
  line-height: 1.6;
  text-decoration: none;
}
.contents a::before {
  content: counter(chapter, decimal-leading-zero);
  font-size: 0.6875rem;
  color: #85858b;
  font-variant-numeric: tabular-nums;
}
.contents a:hover {
  color: #1d1d1f;
}
.document {
  grid-column: 2;
  min-width: 0;
}
.document section {
  margin-bottom: var(--section-gap);
}
.document section:last-child {
  margin-bottom: 0;
}
h2 {
  margin: 0 0 1.25rem;
  font-size: 1.25rem;
  line-height: 1.55;
  font-weight: 600;
  letter-spacing: -0.015em;
  scroll-margin-top: 7rem;
}
h3 {
  margin: 1.75rem 0 0.625rem;
  font-size: 0.9375rem;
  font-weight: 600;
  line-height: 1.7;
}
.document p {
  margin: 0 0 1rem;
  color: var(--body);
  font-size: 0.9375rem;
  line-height: 1.95;
  overflow-wrap: anywhere;
}
.document strong {
  color: #1d1d1f;
  font-weight: 600;
}
.document p:last-child {
  margin-bottom: 0;
}
.site-footer {
  max-width: calc(var(--page-max) - 5rem);
  margin: 0 auto;
  padding: 1.75rem 0 2.5rem;
  border-top: 1px solid var(--line);
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  color: var(--muted);
  font-size: 0.75rem;
  line-height: 1.8;
}
.footer-brand {
  margin-left: 0.5rem;
}
.site-footer a {
  color: var(--muted);
  text-decoration: none;
}
.site-footer a span {
  margin-left: 0.5rem;
}
.skip {
  position: fixed;
  z-index: 20;
  top: -6rem;
  left: 1rem;
  padding: 0.75rem 1rem;
  background: #fff;
}
.skip:focus {
  top: 1rem;
}
#main {
  scroll-margin-top: 6rem;
}
@media (max-width: 900px) {
  .layout {
    column-gap: var(--space-10);
    grid-template-columns: 11rem minmax(0, 1fr);
  }
  .site-footer {
    margin-inline: var(--page-pad);
  }
}
@media (max-width: 700px) {
  .header-inner {
    min-height: 4.5rem;
    padding: var(--space-3) var(--space-5);
    gap: var(--space-3);
  }
  .brand-logo {
    height: 1.625rem;
  }
  .page-nav a {
    padding: 0.65rem var(--space-3);
    min-height: 2.5rem;
  }
  .layout {
    display: block;
    padding: var(--space-10) var(--space-6) var(--space-14);
  }
  .document-heading {
    padding-bottom: 1.75rem;
    margin-bottom: 0;
  }
  .introduction {
    font-size: 1rem;
    margin-bottom: 1.25rem;
  }
  .sidebar {
    position: static;
    margin-bottom: 2rem;
    border-bottom: 1px solid var(--line);
  }
  .contents {
    padding-block: 0.5rem;
  }
  .contents summary {
    font-size: 0.875rem;
  }
  .contents ol {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 0 var(--space-4);
    padding: 0 0 0.75rem;
  }
  .contents a {
    font-size: 0.75rem;
    gap: 0.5rem;
    min-height: 2.75rem;
  }
  .document section {
    margin-bottom: var(--space-10);
  }
  h2 {
    font-size: 1.125rem;
    scroll-margin-top: 6rem;
  }
  .document p {
    font-size: 0.9375rem;
  }
  .site-footer {
    margin-inline: var(--space-6);
    padding-block: 1.5rem 2rem;
  }
}
@media (max-width: 360px) {
  .contents ol {
    grid-template-columns: 1fr;
  }
}
@media (prefers-reduced-transparency: reduce) {
  .site-header {
    background: #fff;
    backdrop-filter: none;
  }
}
@media (prefers-contrast: more) {
  :root {
    --muted: #333;
    --line: #777;
  }
  .site-header {
    background: #fff;
    backdrop-filter: none;
  }
  .document p {
    color: #1d1d1f;
  }
}
@media print {
  .site-header,
  .sidebar,
  .skip,
  .site-footer {
    display: none;
  }
  .layout {
    display: block;
    max-width: none;
    padding: 0;
  }
  .document-heading {
    margin-bottom: 2rem;
  }
  h2,
  h3 {
    break-after: avoid;
  }
  p {
    orphans: 3;
    widows: 3;
  }
  a {
    color: inherit;
  }
}