:root {
  --bg: #ffffff;
  --sidebar-bg: #fbfbfa;
  --text: #37352f;
  --text-light: #9b9a97;
  --border: #ebece9;
  --hover: rgba(55, 53, 47, .08);
  --accent: #2383e2;
}
* { box-sizing: border-box; }

body {
  margin: 0;
  display: grid;
  grid-template-columns: 16.5rem minmax(0, 1fr) 16rem;
  font: 16px/1.65 -apple-system, BlinkMacSystemFont, "Segoe UI", "Helvetica Neue", Helvetica, Arial, sans-serif;
  color: var(--text);
  background: var(--bg);
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

.chapters, .on-this-page {
  position: sticky;
  top: 0;
  align-self: start;
  max-height: 100vh;
  overflow-y: auto;
  padding: 1.75rem 1rem;
  font-size: .9rem;
}
.chapters { background: var(--sidebar-bg); border-right: 1px solid var(--border); }
.brand { display: block; font-size: 1.05rem; font-weight: 600; color: var(--text); margin: .2rem .5rem 1.5rem; }
.chapters ol { list-style: none; margin: 0; padding: 0; counter-reset: ch; display: flex; flex-direction: column; gap: 1px; }
.chapters li { counter-increment: ch; }
.chapters li a { display: flex; gap: .55rem; align-items: baseline; padding: .4rem .5rem; border-radius: 6px; color: var(--text); }
.chapters li a::before { content: counter(ch); color: var(--text-light); font-size: .78em; min-width: 1em; }
.chapters li a:hover { background: var(--hover); text-decoration: none; }
.chapters .current a { background: var(--hover); font-weight: 600; }

main { padding: 3rem 4rem 8rem; max-width: 76rem; width: 100%; margin: 0 auto; }
main h1 { margin: 0 0 2rem; font-size: 2.25rem; font-weight: 700; letter-spacing: -.01em; }
main h2 { margin: 2.75rem 0 1rem; font-size: 1.4rem; font-weight: 600; scroll-margin-top: 1.25rem; }
main h3 { margin: 1.75rem 0 .75rem; font-size: 1.1rem; font-weight: 600; scroll-margin-top: 1.25rem; }
main h4 { margin: 1.5rem 0 .5rem; font-size: 1rem; font-weight: 600; scroll-margin-top: 1.25rem; }
main hr { border: 0; border-top: 1px solid var(--border); margin: 2rem 0; }
main table { border-collapse: collapse; width: 100%; margin: 1rem 0; font-size: .92rem; }
main th, main td { border: 1px solid var(--border); padding: .5rem .7rem; text-align: left; vertical-align: top; }
main th { background: var(--sidebar-bg); font-weight: 600; }
main code { background: var(--sidebar-bg); padding: .15rem .35rem; border-radius: 4px; font-size: .85em; }

.on-this-page { border-left: 1px solid var(--border); }
.on-this-page b { display: block; font-size: .72rem; text-transform: uppercase; letter-spacing: .04em; color: var(--text-light); font-weight: 600; margin: 0 0 .75rem .75rem; }
.on-this-page ul { list-style: none; margin: 0; padding: 0; border-left: 1px solid var(--border); }
.on-this-page li a { display: block; padding: .35rem .75rem; margin-left: -1px; border-left: 2px solid transparent; color: var(--text-light); font-size: .85rem; line-height: 1.3; }
.on-this-page li.H3 a { padding-left: 1.5rem; font-size: .8rem; }
.on-this-page li a:hover { color: var(--text); text-decoration: none; }
.on-this-page li a.active { color: var(--accent); border-left-color: var(--accent); font-weight: 500; }

@media (max-width: 60rem) {
  body { grid-template-columns: 1fr; }
  .chapters, .on-this-page { position: static; max-height: none; border: 0; }
  .on-this-page { display: none; }
  main { padding: 1.5rem 1.25rem 4rem; }
}
figure.diagram { margin: 1.5rem 0; text-align: center; }