:root {
  color-scheme: light;
  --page: #f9f9f7;
  --surface: #fcfcfb;
  --ink: #0b0b0b;
  --ink-2: #52514e;
  --muted: #898781;
  --hair: #e1e0d9;
  --axis: #c3c2b7;
  --accent: #2a78d6;
  --accent-ink: #1c5cab;
  --tint: #eef4fc;
  --warn-tint: #fdf3e2;
  --warn: #c98500;
  --font: "PingFang SC", "Noto Sans SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, sans-serif;
}
* { box-sizing: border-box; }
html { font-size: 17px; -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--page); color: var(--ink); font-family: var(--font); line-height: 1.85; }
a { color: var(--accent-ink); text-decoration: none; }
a:hover { text-decoration: underline; }

header.top { position: sticky; top: 0; z-index: 5; display: flex; align-items: center; gap: 1rem;
  padding: .6rem 1.5rem; background: rgba(249,249,247,.92); backdrop-filter: blur(6px); border-bottom: 1px solid var(--hair); }
.brand { font-weight: 700; color: var(--ink); letter-spacing: .02em; }
.menu { display: none; margin-left: auto; font-size: .9rem; }
.menu summary { cursor: pointer; color: var(--ink-2); }
.menu ol { position: absolute; right: 1rem; background: var(--surface); border: 1px solid var(--hair); border-radius: 8px; padding: .6rem 1rem .6rem 1.4rem; margin: .4rem 0 0; list-style: none; }

.layout { display: grid; grid-template-columns: 13rem minmax(0, 46rem) 14rem; gap: 2.5rem; justify-content: center; padding: 0 1.5rem; }
nav.chapters, aside.toc { position: sticky; top: 3.6rem; align-self: start; max-height: calc(100vh - 4rem); overflow-y: auto; padding: 2rem 0; font-size: .86rem; }
nav.chapters ol, .menu ol { list-style: none; padding: 0; margin: 0; }
nav.chapters li, .menu li { margin: .1rem 0; }
nav.chapters a, .menu a { display: block; padding: .25rem .6rem; border-radius: 6px; color: var(--ink-2); }
nav.chapters a.current, .menu a.current { background: var(--tint); color: var(--accent-ink); font-weight: 600; }
aside.toc .toc-title { color: var(--muted); font-size: .78rem; margin-bottom: .3rem; }
aside.toc ul { list-style: none; padding-left: 0; margin: 0; }
aside.toc ul ul { padding-left: .8rem; }
aside.toc a { display: block; padding: .15rem 0; color: var(--ink-2); line-height: 1.5; }

main { padding: 2.2rem 0 4rem; min-width: 0; }
article { background: var(--surface); border: 1px solid var(--hair); border-radius: 12px; padding: 2.4rem 2.8rem; }
article h1 { font-size: 1.75rem; line-height: 1.4; margin: 0 0 1.2rem; }
article h2 { font-size: 1.32rem; line-height: 1.45; margin: 2.6rem 0 .8rem; padding-top: 1.4rem; border-top: 1px solid var(--hair); }
article h3 { font-size: 1.08rem; margin: 1.8rem 0 .5rem; }
article h4 { font-size: 1rem; margin: 1.4rem 0 .4rem; color: var(--ink-2); }
.headerlink { margin-left: .4rem; color: var(--axis); visibility: hidden; font-weight: 400; }
h2:hover .headerlink, h3:hover .headerlink { visibility: visible; }
article p, article li { color: var(--ink); }
article strong { font-weight: 650; }
blockquote { margin: 1.2rem 0; padding: .2rem 1rem; border-left: 3px solid var(--axis); color: var(--ink-2); }
code { font-family: "JetBrains Mono", ui-monospace, Menlo, monospace; font-size: .86em; background: #f1f0ec; padding: .1em .35em; border-radius: 4px; }
pre { background: #f4f3ef; border: 1px solid var(--hair); border-radius: 8px; padding: 1rem 1.2rem; overflow-x: auto; line-height: 1.6; }
pre code { background: none; padding: 0; }

table { display: block; overflow-x: auto; border-collapse: collapse; margin: 1.2rem 0; font-size: .9rem; line-height: 1.6; font-variant-numeric: tabular-nums; }
th, td { padding: .5rem .8rem; border-bottom: 1px solid var(--hair); text-align: left; vertical-align: top; }
th { color: var(--ink-2); font-weight: 600; border-bottom: 1.5px solid var(--axis); white-space: nowrap; }
tr:last-child td { border-bottom: none; }

figure { margin: 2rem 0; }
figure img { display: block; width: 100%; height: auto; }
figcaption { margin-top: .6rem; font-size: .86rem; color: var(--ink-2); line-height: 1.6; }
figcaption b { color: var(--ink); }

.admonition { margin: 1.4rem 0; padding: .8rem 1.1rem; border-radius: 8px; background: var(--tint); border-left: 3px solid var(--accent); }
.admonition.warning, .admonition.danger, .admonition.caution { background: var(--warn-tint); border-left-color: var(--warn); }
.admonition-title { margin: 0 0 .3rem; font-weight: 650; }
.admonition p:last-child { margin-bottom: 0; }
.footnote { font-size: .86rem; color: var(--ink-2); }
.katex-display { overflow-x: auto; overflow-y: hidden; padding: .3rem 0; }

nav.pager { display: flex; gap: 1rem; margin-top: 1.6rem; }
nav.pager a { flex: 1; padding: .9rem 1.1rem; background: var(--surface); border: 1px solid var(--hair); border-radius: 10px; color: var(--ink); line-height: 1.5; }
nav.pager a:hover { border-color: var(--accent); text-decoration: none; }
nav.pager a span { display: block; font-size: .78rem; color: var(--muted); }
nav.pager .next { text-align: right; }
footer { text-align: center; color: var(--muted); font-size: .8rem; padding: 0 1rem 2.5rem; }

@media (max-width: 1240px) { .layout { grid-template-columns: 12rem minmax(0, 46rem); } aside.toc { display: none; } }
@media (max-width: 860px) {
  .layout { grid-template-columns: minmax(0, 1fr); padding: 0 .8rem; }
  nav.chapters { display: none; }
  .menu { display: block; }
  article { padding: 1.6rem 1.2rem; border-radius: 10px; }
  html { font-size: 16px; }
}

article h2, article h3, figure { scroll-margin-top: 4.2rem; }