:root {
  --bg: #fbfbfa;
  --paper: #ffffff;
  --ink: #1b1d1f;
  --muted: #666d73;
  --line: #dfe2e5;
  --soft: #f4f5f5;
  --accent: #315f7d;
  --code-bg: #f5f6f7;
  --sidebar: 250px;
  --measure: 780px;
}

* { box-sizing: border-box; }

html {
  scroll-behavior: smooth;
  scroll-padding-top: 5rem;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: Georgia, "Times New Roman", serif;
  font-size: 18px;
  line-height: 1.72;
  text-rendering: optimizeLegibility;
}

a {
  color: var(--accent);
  text-decoration-thickness: 1px;
  text-underline-offset: 0.14em;
}

a:hover { text-decoration-thickness: 2px; }

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
}

.skip-link:focus {
  left: 1rem;
  top: 1rem;
  z-index: 100;
  background: var(--paper);
  border: 1px solid var(--line);
  padding: .5rem .75rem;
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 20;
  border-bottom: 1px solid var(--line);
  background: color-mix(in srgb, var(--bg) 94%, transparent);
  backdrop-filter: blur(10px);
}

.topbar-inner {
  max-width: 1240px;
  margin: 0 auto;
  min-height: 56px;
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.5rem;
  font-family: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

.wordmark {
  color: var(--ink);
  font-weight: 650;
  letter-spacing: -0.015em;
  text-decoration: none;
}

.toplinks {
  display: flex;
  gap: 1rem;
  font-size: .84rem;
}

.toplinks a {
  color: var(--muted);
  text-decoration: none;
}

.page-grid {
  display: grid;
  grid-template-columns: var(--sidebar) minmax(0, var(--measure));
  gap: 64px;
  justify-content: center;
  align-items: start;
  max-width: 1240px;
  margin: 0 auto;
  padding: 64px 24px 120px;
}

.sidebar {
  position: sticky;
  top: 88px;
  max-height: calc(100vh - 112px);
  overflow: auto;
  font-family: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 13px;
  line-height: 1.4;
}

.sidebar-kicker {
  margin-bottom: .8rem;
  color: var(--muted);
  font-size: 11px;
  font-weight: 700;
  letter-spacing: .12em;
  text-transform: uppercase;
}

.toc ol,
.mobile-toc ol {
  margin: 0;
  padding: 0;
  list-style: none;
}

.toc li + li,
.mobile-toc li + li { margin-top: .34rem; }

.toc a,
.mobile-toc a {
  display: block;
  color: var(--muted);
  text-decoration: none;
  padding: .18rem 0;
}

.toc a:hover,
.mobile-toc a:hover { color: var(--ink); }

.toc .appendix-start { margin-top: 1rem; }

.sidebar-note {
  margin-top: 1.5rem;
  padding-top: 1rem;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: 11px;
  line-height: 1.5;
}

.paper {
  min-width: 0;
  padding: 0 4px;
}

.paper-header {
  margin: 0 0 5rem;
  padding-bottom: 2rem;
  border-bottom: 1px solid var(--line);
}

.paper-header .eyebrow {
  margin: 0 0 1rem;
  color: var(--muted);
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: .72rem;
  font-weight: 700;
  letter-spacing: .14em;
  text-transform: uppercase;
}

.paper-header h1 {
  margin: 0;
  max-width: 18ch;
  font-family: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: clamp(2.5rem, 6vw, 4.8rem);
  line-height: .98;
  letter-spacing: -.045em;
}

.paper-header .subtitle {
  max-width: 46rem;
  margin: 1.6rem 0 0;
  color: var(--muted);
  font-size: 1.16rem;
  line-height: 1.55;
}

.paper-header .meta {
  display: flex;
  flex-wrap: wrap;
  gap: .6rem 1rem;
  margin-top: 1.4rem;
  color: var(--muted);
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: .78rem;
}

.section-anchor {
  display: block;
  height: 1px;
  margin-top: 5.5rem;
}

.paper > .section-anchor:first-of-type { margin-top: 0; }

.paper h1,
.paper h2,
.paper h3,
.paper h4 {
  color: var(--ink);
  font-family: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  letter-spacing: -.025em;
  line-height: 1.2;
}

.paper h1 {
  margin: 1rem 0 1.4rem;
  font-size: 2.05rem;
}

.paper h2 {
  margin: 3rem 0 1rem;
  padding-top: .3rem;
  font-size: 1.45rem;
}

.paper h3 {
  margin: 2.1rem 0 .75rem;
  font-size: 1.13rem;
}

.paper p,
.paper ul,
.paper ol { margin-top: 0; margin-bottom: 1.25rem; }

.paper li + li { margin-top: .35rem; }

.paper strong { font-weight: 700; }

.paper hr {
  margin: 3rem 0;
  border: 0;
  border-top: 1px solid var(--line);
}

.paper blockquote {
  margin: 1.8rem 0;
  padding: .2rem 0 .2rem 1.2rem;
  border-left: 3px solid var(--line);
  color: #4e555b;
}

.paper code {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
  font-size: .84em;
}

.paper :not(pre) > code {
  border: 1px solid var(--line);
  border-radius: 4px;
  background: var(--code-bg);
  padding: .08em .3em;
}

.paper pre {
  overflow-x: auto;
  margin: 1.6rem 0;
  border: 1px solid var(--line);
  border-radius: 7px;
  background: var(--code-bg);
  padding: 1rem 1.1rem;
  font-size: .82rem;
  line-height: 1.55;
}

.paper table {
  display: block;
  width: 100%;
  max-width: 100%;
  overflow-x: auto;
  margin: 1.8rem 0;
  border-collapse: collapse;
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: .79rem;
  line-height: 1.45;
}

.paper th,
.paper td {
  padding: .62rem .72rem;
  border: 1px solid var(--line);
  text-align: left;
  vertical-align: top;
}

.paper th { background: var(--soft); }

.paper img,
.mermaid-diagram svg {
  display: block;
  max-width: 100%;
  height: auto;
  margin: 2rem auto;
}

.mermaid-diagram {
  overflow-x: auto;
  margin: 2rem 0;
  padding: .75rem;
}

.source-note {
  margin: 1.1rem 0 0;
  color: var(--muted);
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: .72rem;
}

.footer {
  border-top: 1px solid var(--line);
  padding: 32px 24px 48px;
  color: var(--muted);
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: .78rem;
  text-align: center;
}

.mobile-toc { display: none; }

@media (max-width: 980px) {
  .page-grid {
    display: block;
    max-width: 840px;
    padding-top: 36px;
  }

  .sidebar { display: none; }

  .mobile-toc {
    display: block;
    margin: 24px auto 0;
    max-width: 820px;
    padding: 0 24px;
    font-family: ui-sans-serif, system-ui, sans-serif;
    font-size: .84rem;
  }

  .mobile-toc summary {
    cursor: pointer;
    color: var(--muted);
  }

  .mobile-toc nav {
    margin-top: .8rem;
    padding: 1rem;
    border: 1px solid var(--line);
    background: var(--paper);
  }

  .paper-header { margin-bottom: 3.5rem; }
}

@media (max-width: 620px) {
  body { font-size: 17px; }

  .topbar-inner { padding: 0 16px; }
  .toplinks { gap: .65rem; }
  .toplinks a:last-child { display: none; }

  .page-grid {
    padding: 32px 18px 80px;
  }

  .paper-header h1 {
    font-size: clamp(2.2rem, 13vw, 3.3rem);
  }
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #121416;
    --paper: #17191b;
    --ink: #e7e9eb;
    --muted: #a0a7ad;
    --line: #34393e;
    --soft: #202428;
    --accent: #8ab8d8;
    --code-bg: #1b1e21;
  }

  .paper blockquote { color: #b7bdc2; }
}

@media print {
  :root {
    --bg: #fff;
    --paper: #fff;
    --ink: #000;
    --muted: #444;
    --line: #bbb;
  }

  .topbar,
  .sidebar,
  .mobile-toc,
  .footer { display: none !important; }

  .page-grid {
    display: block;
    max-width: none;
    margin: 0;
    padding: 0;
  }

  .paper {
    max-width: none;
    font-size: 11pt;
  }

  .paper-header {
    min-height: 65vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    page-break-after: always;
  }

  .section-anchor { page-break-before: always; }

  a { color: inherit; text-decoration: none; }

  pre, table, blockquote { break-inside: avoid; }
}