/* Statistics Reference — design tokens (fixed spec) */
:root {
  --bg: #FAFAF8;
  --text: #1A1A1A;
  --accent: #2B4C7E;
  --muted: #8A8578;
  --border: #E8E6E0;
  --success: #0F5132;
  --error: #7A1F1F;
  --code-bg: #F3F2EE;
  --accent-tint: #4A6FA5;

  --sans: "Inter", system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --mono: "JetBrains Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;

  --sidebar-w: 240px;
  --radius: 4px;
}

*, *::before, *::after { box-sizing: border-box; }

html { font-size: 16px; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--sans);
  font-size: 1rem;
  line-height: 1.5;
  -webkit-text-size-adjust: 100%;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
a:focus-visible, button:focus-visible, input:focus-visible, summary:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.muted { color: var(--muted); }
.visually-hidden {
  position: absolute; width: 1px; height: 1px; overflow: hidden;
  clip: rect(0 0 0 0); white-space: nowrap;
}
.skip { position: absolute; left: -9999px; }
.skip:focus { left: 1rem; top: 1rem; background: var(--bg); padding: .25rem .5rem; z-index: 10; }

/* ------------------------------------------------------------------ *
 * Layout: fixed 240px sidebar + main column (max 760px, left-aligned)
 * ------------------------------------------------------------------ */

.topbar { display: none; }

.sidebar {
  position: fixed;
  inset: 0 auto 0 0;
  width: var(--sidebar-w);
  overflow-y: auto;
  border-right: 1px solid var(--border);
  background: var(--bg);
  padding: 1.25rem 1rem 2rem;
  font-size: .9375rem;
}

main {
  margin-left: var(--sidebar-w);
  padding: 2.5rem 3rem 5rem;
  outline: none;
}

.doc { max-width: 760px; }

/* ------------------------------------------------------------------ *
 * Sidebar
 * ------------------------------------------------------------------ */

.brand { font-weight: 600; letter-spacing: 0; }
.brand-side { margin-bottom: 1.25rem; }

.switch { display: flex; flex-wrap: wrap; gap: .25rem 1rem; margin-bottom: .5rem; }
.switch a { color: var(--muted); font-weight: 400; }
.switch a:hover { color: var(--text); text-decoration: none; }
.switch a.active { color: var(--text); font-weight: 600; }
.switch.sub { padding-bottom: .75rem; margin-bottom: .75rem; border-bottom: 1px solid var(--border); }

.search input {
  width: 100%;
  font: inherit;
  font-size: .9375rem;
  color: var(--text);
  background: #fff;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: .375rem .5rem;
  margin-bottom: 1rem;
}
.search input::placeholder { color: var(--muted); }

.nav a { color: var(--text); display: block; padding: .1875rem 0; }
.nav a:hover { color: var(--accent); text-decoration: none; }
.nav a.current { color: var(--accent); font-weight: 600; }
.nav ul, .nav ol { list-style: none; margin: 0; padding: 0; }
.nav-overview { margin-bottom: .5rem; }
.nav-note { margin: 0 0 .5rem; font-size: .875rem; }

.unit { margin-bottom: .25rem; }
.unit-toggle {
  display: flex;
  align-items: baseline;
  gap: .5rem;
  width: 100%;
  text-align: left;
  font: inherit;
  color: var(--text);
  background: none;
  border: 0;
  padding: .3125rem 0;
  cursor: pointer;
}
.unit-toggle::after {
  content: "+";
  margin-left: auto;
  color: var(--muted);
  font-family: var(--mono);
}
.unit.open .unit-toggle::after { content: "\2212"; }
.unit-num { color: var(--muted); font-family: var(--mono); font-size: .8125rem; min-width: 1ch; }

/* expand / collapse (the only sidebar motion) */
.unit-body {
  display: grid;
  grid-template-rows: 0fr;
  transition: grid-template-rows 160ms ease;
}
.unit.open .unit-body { grid-template-rows: 1fr; }
.unit-body > ul { overflow: hidden; padding-left: 1.3rem; }
.unit-body a { font-size: .9063rem; }
.unit:not(.open) .unit-body a { visibility: hidden; }

.tier-list { counter-reset: t; }
.tier-list li { counter-increment: t; display: flex; gap: .5rem; }
.tier-list li::before {
  content: counter(t);
  color: var(--muted);
  font-family: var(--mono);
  font-size: .8125rem;
  padding-top: .25rem;
  min-width: 1.25rem;
}

.results li { border-top: 1px solid var(--border); }
.results a { padding: .5rem 0; }
.r-title { display: block; }
.r-where { display: block; font-size: .8125rem; }
.r-snip { display: block; font-size: .8125rem; color: var(--muted); line-height: 1.4; margin-top: .125rem; }
mark { background: none; color: var(--text); font-weight: 600; }

/* ------------------------------------------------------------------ *
 * Document typography (1.25 modular scale, no serif, no caps)
 * ------------------------------------------------------------------ */

.doc h1, .doc h2, .doc h3, .doc h4 { font-weight: 600; line-height: 1.25; color: var(--text); }
.doc h1 { font-size: 1.953rem; margin: 0 0 1rem; }
.doc h2 { font-size: 1.563rem; margin: 2.5rem 0 .75rem; padding-top: 1.25rem; border-top: 1px solid var(--border); }
.doc h3 { font-size: 1.25rem; margin: 1.75rem 0 .5rem; }
.doc h4 { font-size: 1rem; margin: 1.25rem 0 .5rem; }
.doc p { margin: 0 0 1rem; }
.doc ul, .doc ol { margin: 0 0 1rem; padding-left: 1.5rem; }
.doc li { margin: .25rem 0; }
.doc li > ul, .doc li > ol { margin: .25rem 0 .25rem; }
.doc strong { font-weight: 600; }

.crumb { color: var(--muted); font-size: .875rem; margin: 0 0 .5rem !important; }
.lead { font-size: 1.0625rem; }

.source { color: var(--muted); font-size: .875rem; margin: -.25rem 0 1.5rem; }
.source p { margin: 0; }

blockquote {
  margin: 0 0 1rem;
  padding: 0 0 0 1rem;
  border-left: 2px solid var(--border);
  color: var(--muted);
}

/* inline code and numbers */
code {
  font-family: var(--mono);
  font-size: .875em;
  background: var(--code-bg);
  border-radius: 3px;
  padding: .0625rem .25rem;
}

/* tables */
.table-wrap { overflow-x: auto; margin: 0 0 1.25rem; }
table { border-collapse: collapse; width: 100%; font-size: .9375rem; }
th, td { text-align: left; vertical-align: top; padding: .4375rem .75rem .4375rem 0; border-bottom: 1px solid var(--border); }
th { font-weight: 600; border-bottom-color: var(--text); }
td:first-child, th:first-child { padding-left: 0; }

/* math */
.katex { font-size: 1.05em; }
.math-block, .katex-display { overflow-x: auto; overflow-y: hidden; }
.katex-display { margin: .75rem 0 1rem; }

/* ------------------------------------------------------------------ *
 * Code blocks — the visual anchor
 * ------------------------------------------------------------------ */

.code-block {
  position: relative;
  margin: 0 0 1.5rem;
  background: var(--code-bg);
  border-left: 3px solid var(--accent);
  border-radius: 0 var(--radius) var(--radius) 0;
}

.code-bar {
  display: flex;
  align-items: stretch;
  gap: 1.25rem;
  padding: 0 1rem;
  border-bottom: 1px solid var(--border);
  font-size: .875rem;
}

.tab, .tab-label {
  font: inherit;
  color: var(--muted);
  background: none;
  border: 0;
  border-bottom: 2px solid transparent;
  padding: .5rem 0 .4375rem;
  margin-bottom: -1px;
}
.tab { cursor: pointer; }
.tab:hover { color: var(--text); }
.tab[aria-selected="true"], .tab-label { color: var(--text); font-weight: 600; border-bottom-color: var(--accent); }

.copy {
  margin-left: auto;
  font: inherit;
  font-size: .8125rem;
  color: var(--muted);
  background: none;
  border: 1px solid transparent;
  border-radius: var(--radius);
  padding: .25rem .5rem;
  align-self: center;
  cursor: pointer;
}
.copy:hover { color: var(--text); border-color: var(--border); }
.copy.ok { color: var(--success); }
.copy.fail { color: var(--error); }

.panel, pre.plain {
  margin: 0;
  padding: 1rem 1rem 1.125rem;
  overflow-x: auto;
  font-family: var(--mono);
  font-size: .8438rem;
  line-height: 1.55;
  tab-size: 4;
}
.panel { animation: tab-in 120ms ease-out; }
.panel code, pre.plain code { background: none; padding: 0; font-size: inherit; border-radius: 0; }
pre.plain { background: var(--code-bg); border-left: 3px solid var(--accent); margin-bottom: 1rem; }

@keyframes tab-in { from { opacity: 0; } to { opacity: 1; } }

/* syntax colours: muted, within the palette */
.hljs-comment, .hljs-quote { color: var(--muted); font-style: italic; }
.hljs-keyword, .hljs-built_in, .hljs-literal, .hljs-selector-tag { color: var(--accent); font-weight: 600; }
.hljs-string, .hljs-regexp, .hljs-subst { color: var(--accent-tint); }
.hljs-number, .hljs-symbol { color: var(--text); }
.hljs-title, .hljs-title.function_, .hljs-function .hljs-title { color: var(--text); font-weight: 600; }
.hljs-params, .hljs-variable, .hljs-attr, .hljs-property { color: var(--text); }
.hljs-meta { color: var(--muted); }

/* ------------------------------------------------------------------ *
 * Solutions, connections, overview, prev/next
 * ------------------------------------------------------------------ */

details.solutions { border: 1px solid var(--border); border-radius: var(--radius); padding: 0 1rem; }
details.solutions > summary { cursor: pointer; padding: .625rem 0; color: var(--accent); }
details.solutions[open] > summary { border-bottom: 1px solid var(--border); margin-bottom: .75rem; }

.connections h3 { font-size: 1rem; margin: 1.25rem 0 .375rem; }
.links { list-style: none; padding-left: 0 !important; }
.links li { margin: .25rem 0; }
.links .muted { font-size: .875rem; }

.overview-list { padding-left: 1.5rem; }
.overview-list li { margin: .375rem 0; }
.overview-list.described li { margin: 0 0 1rem; }
.overview-list.described p { margin: .125rem 0 0; color: var(--muted); font-size: .9375rem; }

.prevnext {
  display: flex;
  justify-content: space-between;
  gap: 1.5rem;
  margin-top: 3rem;
  padding-top: 1.25rem;
  border-top: 1px solid var(--border);
}
.prevnext a { display: flex; flex-direction: column; max-width: 48%; }
.prevnext .next { text-align: right; margin-left: auto; }
.prevnext .muted { font-size: .8125rem; }

.error { color: var(--error); }

/* ------------------------------------------------------------------ *
 * Responsive: sidebar becomes a top dropdown under 768px
 * ------------------------------------------------------------------ */

@media (max-width: 767.98px) {
  .topbar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    position: sticky;
    top: 0;
    z-index: 5;
    background: var(--bg);
    border-bottom: 1px solid var(--border);
    padding: .625rem 1rem;
  }
  #menu-toggle {
    font: inherit;
    color: var(--accent);
    background: none;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: .25rem .625rem;
    cursor: pointer;
  }
  #menu-toggle[aria-expanded="true"] { color: var(--text); font-weight: 600; }

  .sidebar {
    display: none;
    position: static;
    width: auto;
    border-right: 0;
    border-bottom: 1px solid var(--border);
    max-height: 70vh;
    padding-top: 1rem;
  }
  body.menu-open .sidebar { display: block; }
  .brand-side { display: none; }

  main { margin-left: 0; padding: 1.5rem 1rem 4rem; }
  .doc h1 { font-size: 1.563rem; }
  .doc h2 { font-size: 1.25rem; }
  .prevnext a { max-width: 100%; }
}

@media (prefers-reduced-motion: reduce) {
  .unit-body { transition: none; }
  .panel { animation: none; }
}

@media print {
  .sidebar, .topbar, .copy, .prevnext { display: none; }
  main { margin: 0; padding: 0; }
}

/* external (Wikipedia) links: open in a new tab, marked with a small arrow */
a.ext { text-decoration: underline; text-decoration-style: dotted; text-underline-offset: 2px; }
a.ext::after { content: "\2197"; font-size: .7em; margin-left: .1em; vertical-align: super; opacity: .6; }
.q-original { color: var(--accent); font-weight: 600; }