:root {
  color-scheme: light dark;
  --bg: #f5f4ef;
  --paper: #fffdf8;
  --text: #27313b;
  --heading: #14212b;
  --muted: #68737e;
  --line: #d9dde2;
  --accent: #176b78;
  --accent-soft: #e8f3f4;
  --code-bg: #eef1f3;
  --shadow: 0 14px 44px rgba(26, 35, 44, .09);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  background: var(--bg);
  color: var(--text);
  font: 18px/1.68 Georgia, "Times New Roman", serif;
  margin: 0;
}

a { color: var(--accent); }
.site-nav {
  align-items: center;
  background: color-mix(in srgb, var(--paper) 92%, transparent);
  border-bottom: 1px solid var(--line);
  display: flex;
  font: 600 .92rem/1.2 Inter, ui-sans-serif, system-ui, sans-serif;
  justify-content: space-between;
  padding: 1rem max(20px, calc((100vw - 1040px) / 2));
  position: sticky;
  top: 0;
  z-index: 10;
}
.site-nav a { color: var(--heading); text-decoration: none; }
.theme-toggle { background: none; border: 0; color: var(--heading); cursor: pointer; font-size: 1.1rem; }
.reading-progress {
  background: transparent;
  bottom: -1px;
  height: 2px;
  left: 0;
  position: absolute;
  right: 0;
}
.reading-progress span {
  background: var(--accent);
  display: block;
  height: 100%;
  transform: scaleX(0);
  transform-origin: left;
  transition: transform .08s linear;
}

.article-layout {
  align-items: start;
  display: grid;
  gap: 34px;
  grid-template-columns: 230px minmax(0, 900px);
  justify-content: center;
  margin: 0 auto;
  max-width: 1220px;
  padding: 0 24px;
}
.chapter-sidebar {
  margin-top: 48px;
  max-height: calc(100vh - 96px);
  overflow-y: auto;
  position: sticky;
  top: 82px;
}
.chapter-card {
  border-left: 1px solid var(--line);
  font: .84rem/1.35 Inter, ui-sans-serif, system-ui, sans-serif;
  padding: .35rem 0 .35rem 1rem;
}
.chapter-label {
  color: var(--heading);
  font-size: .72rem;
  font-weight: 700;
  letter-spacing: .08em;
  margin-bottom: .65rem;
  text-transform: uppercase;
}
.chapter-list { list-style: none; margin: 0; padding: 0; }
.chapter-list li { margin: 0; }
.chapter-list a {
  border-left: 2px solid transparent;
  color: var(--muted);
  display: block;
  margin-left: calc(-1rem - 1px);
  padding: .38rem .5rem .38rem calc(1rem - 1px);
  text-decoration: none;
  transition: background .18s ease, border-color .18s ease, color .18s ease;
}
.chapter-list a:hover {
  background: color-mix(in srgb, var(--accent-soft) 65%, transparent);
  color: var(--heading);
}
.chapter-list a.active {
  background: var(--accent-soft);
  border-left-color: var(--accent);
  color: var(--accent);
  font-weight: 700;
}
.chapter-select {
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: 7px;
  color: var(--heading);
  display: none;
  font: 600 .86rem/1.2 Inter, ui-sans-serif, system-ui, sans-serif;
  padding: .7rem 2.2rem .7rem .8rem;
  width: 100%;
}

.page {
  background: var(--paper);
  box-shadow: var(--shadow);
  margin: 48px 0;
  max-width: 900px;
  padding: 58px clamp(24px, 7vw, 78px);
  width: 100%;
}
.article-header { border-bottom: 1px solid var(--line); margin-bottom: 2rem; padding-bottom: 1.8rem; }
.category, .meta, .eyebrow {
  color: var(--muted);
  font: 600 .82rem/1.4 Inter, ui-sans-serif, system-ui, sans-serif;
  letter-spacing: .04em;
  text-transform: uppercase;
}
h1, h2, h3 { color: var(--heading); font-family: Inter, ui-sans-serif, system-ui, sans-serif; line-height: 1.2; }
h1 { font-size: clamp(2.2rem, 6vw, 3.65rem); letter-spacing: -.045em; margin: .65rem 0 1rem; }
h2 { font-size: 1.65rem; letter-spacing: -.025em; margin: 3.2rem 0 .8rem; scroll-margin-top: 5rem; }
h3 { font-size: 1.15rem; margin: 1.8rem 0 .45rem; scroll-margin-top: 5rem; }
.dek { color: var(--muted); font: 1.18rem/1.55 Inter, ui-sans-serif, system-ui, sans-serif; margin: 0 0 1.2rem; }
p, li { max-width: 70ch; }
li + li { margin-top: .35rem; }
blockquote { border-left: 4px solid var(--accent); color: var(--heading); font-size: 1.12em; margin: 1.7rem 0; padding: .15rem 1.2rem; }
table { border-collapse: collapse; display: block; font: .88rem/1.5 Inter, ui-sans-serif, system-ui, sans-serif; margin: 1.4rem 0; overflow-x: auto; width: 100%; }
th, td { border: 1px solid var(--line); padding: .72rem .78rem; text-align: left; vertical-align: top; }
th { background: var(--accent-soft); color: var(--heading); }
code, pre { font-family: "SFMono-Regular", Consolas, monospace; font-size: .86em; }
code { background: var(--code-bg); border-radius: 4px; padding: .12rem .3rem; }
pre { background: var(--code-bg); border-radius: 9px; line-height: 1.55; overflow-x: auto; padding: 1rem; }
pre code { background: none; padding: 0; }
.callout {
  background: var(--accent-soft);
  border: 1px solid color-mix(in srgb, var(--accent) 24%, var(--line));
  border-radius: 10px;
  font-family: Inter, ui-sans-serif, system-ui, sans-serif;
  margin: 2rem 0;
  padding: 1rem 1.25rem;
}
.callout strong { color: var(--heading); }
.callout p:first-child { margin-top: 0; }
.callout p:last-child { margin-bottom: 0; }
.button-link {
  background: var(--accent);
  border-radius: 7px;
  color: white;
  display: inline-block;
  font: 600 .9rem/1.2 Inter, ui-sans-serif, system-ui, sans-serif;
  padding: .75rem 1rem;
  text-decoration: none;
}
.source-list { font-size: .92rem; }
footer { border-top: 1px solid var(--line); color: var(--muted); font: .84rem/1.55 Inter, ui-sans-serif, system-ui, sans-serif; margin-top: 3.5rem; padding-top: 1.2rem; }

html.dark {
  --bg: #0f1215;
  --paper: #181c21;
  --text: #d7dde2;
  --heading: #f3f6f8;
  --muted: #aab4bd;
  --line: #39414a;
  --accent: #72cad6;
  --accent-soft: #1d353a;
  --code-bg: #252b32;
  --shadow: none;
}

@media (prefers-color-scheme: dark) {
  html:not(.light) {
    --bg: #0f1215;
    --paper: #181c21;
    --text: #d7dde2;
    --heading: #f3f6f8;
    --muted: #aab4bd;
    --line: #39414a;
    --accent: #72cad6;
    --accent-soft: #1d353a;
    --code-bg: #252b32;
    --shadow: none;
  }
}

@media (max-width: 1050px) {
  .article-layout {
    display: block;
    max-width: 900px;
    padding: 0;
  }
  .chapter-sidebar {
    backdrop-filter: blur(12px);
    background: color-mix(in srgb, var(--paper) 94%, transparent);
    border-bottom: 1px solid var(--line);
    margin: 0;
    max-height: none;
    overflow: visible;
    padding: .65rem max(22px, calc((100vw - 820px) / 2));
    position: sticky;
    top: 52px;
    z-index: 8;
  }
  .chapter-card { border: 0; padding: 0; }
  .chapter-label, .chapter-list { display: none; }
  .chapter-select { display: block; }
  .page { margin: 28px auto 48px; }
}

@media (max-width: 650px) {
  body { font-size: 17px; }
  .page { margin: 0; padding: 38px 22px; }
  .chapter-sidebar { top: 52px; }
  h2, h3 { scroll-margin-top: 8rem; }
}

@media print {
  :root, html.dark, html:not(.light) {
    --bg: white;
    --paper: white;
    --text: #27313b;
    --heading: #14212b;
    --muted: #68737e;
    --line: #d9dde2;
    --accent: #176b78;
    --accent-soft: #e8f3f4;
    --code-bg: #eef1f3;
  }
  .site-nav, .theme-toggle, .chapter-sidebar { display: none; }
  .article-layout { display: block; max-width: none; padding: 0; }
  .page { box-shadow: none; margin: 0; max-width: none; }
}