/* Static content pages (/guide, /models/*): plain HTML served by nginx,
   readable without JavaScript. Colors follow the app's tokens (index.css). */
:root {
  color-scheme: light dark;
  --bg: #f6f7f8;
  --raised: #ffffff;
  --text: #1b2430;
  --text-dim: #5b6572;
  --border: #d5dbe1;
  --link: #1d5c99;
  --primary: #1d5c99;
  --on-primary: #ffffff;
  --node-ni: #e2ecf6;
  --node-ni-stroke: #1d5c99;
  --node-i: #f7e3e7;
  --node-i-stroke: #b42341;
  --arrow-transfer: #3b4a5c;
  --arrow-new: #b42341;
  --arrow-outs: #946a13;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #14181d;
    --raised: #212730;
    --text: #e3e7ec;
    --text-dim: #9aa4b0;
    --border: #2c343e;
    --link: #8bb8e8;
    --primary: #7fb0e3;
    --on-primary: #10151b;
    --node-ni: #1b2c40;
    --node-ni-stroke: #7fb0e3;
    --node-i: #3a1d26;
    --node-i-stroke: #e8758a;
    --arrow-transfer: #b8c3d0;
    --arrow-new: #e8758a;
    --arrow-outs: #d9ae55;
  }
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  font-size: 1.0625rem;
  line-height: 1.6;
}
a { color: var(--link); }

.site-header {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px 20px;
  max-width: 46rem;
  margin: 0 auto;
  padding: 16px;
}
.wordmark {
  font-family: "STIX Two Text", "Cambria Math", "Times New Roman", serif;
  font-size: 1.4rem;
  font-weight: 600;
  color: var(--text);
  text-decoration: none;
  margin-right: auto;
}
.site-header nav { display: flex; flex-wrap: wrap; gap: 4px 16px; align-items: center; }
.site-header nav a { text-decoration: none; font-weight: 600; }
.site-header nav a[aria-current="page"] { color: var(--text); }

/* "Models" menu in the header: a <details> dropdown, no JavaScript */
.nav-menu { position: relative; }
.nav-menu summary {
  cursor: pointer;
  font-weight: 600;
  color: var(--link);
  list-style: none;
}
.nav-menu summary::-webkit-details-marker { display: none; }
.nav-menu summary::after { content: " ▾"; font-size: 0.8em; }
.nav-menu[open] summary::after { content: " ▴"; }
.nav-menu.is-current summary { color: var(--text); }
.nav-menu ul {
  position: absolute;
  z-index: 10;
  left: 0;
  top: calc(100% + 6px);
  min-width: 15rem;
  margin: 0;
  padding: 6px 0;
  list-style: none;
  background: var(--raised);
  border: 1px solid var(--border);
  border-radius: 4px;
  box-shadow: 0 6px 20px rgba(0, 0, 0, 0.18);
}
.site-header .nav-menu li a { display: block; padding: 6px 14px; }
.cta {
  display: inline-block;
  padding: 8px 14px;
  border-radius: 4px;
  background: var(--primary);
  color: var(--on-primary) !important;
  font-weight: 600;
  text-decoration: none;
}

main { max-width: 46rem; margin: 0 auto; padding: 0 16px 48px; }
.breadcrumb { font-size: 0.9rem; color: var(--text-dim); margin: 8px 0 0; }
.breadcrumb ol { list-style: none; display: flex; flex-wrap: wrap; gap: 6px; margin: 0; padding: 0; }
.breadcrumb li + li::before { content: "›"; margin-right: 6px; }
h1 { font-size: 2rem; line-height: 1.25; margin: 16px 0 8px; }
h2 { font-size: 1.4rem; line-height: 1.3; margin: 40px 0 8px; }
h3 { font-size: 1.1rem; margin: 24px 0 4px; }
.byline { color: var(--text-dim); font-size: 0.95rem; margin: 0 0 24px; }

/* "On this page" table of contents (collapsed on narrow screens) */
.toc {
  border: 1px solid var(--border);
  border-radius: 4px;
  background: var(--raised);
  padding: 8px 14px;
  margin: 0 0 24px;
  font-size: 0.95rem;
}
.toc summary { cursor: pointer; font-weight: 600; }
.toc ol { margin: 8px 0 4px; padding-left: 1.4rem; }
.toc li { margin: 2px 0; }
@media (min-width: 641px) { .toc ol { columns: 2; column-gap: 32px; } }
.lead { font-size: 1.15rem; }
code, pre { font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: 0.92em; }
pre {
  background: var(--raised);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 12px 14px;
  overflow-x: auto;
  line-height: 1.45;
}
.formula {
  background: var(--raised);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 16px;
  margin: 16px 0;
  overflow-x: auto;
}
.formula math { font-size: 1.5rem; }
.formula p { margin: 8px 0 0; font-size: 0.9rem; color: var(--text-dim); text-align: center; }
.formula math + math { margin-top: 16px; }
/* Aligned equation systems: MathML Core ignores columnalign */
mtable[columnalign^="right left"] > mtr > mtd:nth-child(odd) { text-align: right; padding-right: 0; }
mtable[columnalign^="right left"] > mtr > mtd:nth-child(even) { text-align: left; padding-left: 0; }
mtable[columnalign^="right left"] > mtr > mtd:nth-child(2n+3) { padding-left: 2em; }
/* Very long formulas: smaller, and the LaTeX source wraps */
.formula-long math { font-size: 1.05rem; }
.formula-long pre.latex { margin: 4px 0 0; white-space: pre-wrap; overflow-wrap: anywhere; font-size: 0.8rem; }
details.formula-full { margin: 0 0 16px; }
details.formula-full > summary { cursor: pointer; font-weight: 600; color: var(--link); }
figure { margin: 24px 0; }
figure svg { display: block; width: 100%; max-width: 32rem; height: auto; margin: 0 auto; }
.figure-wide svg { max-width: 40rem; }
figcaption { font-size: 0.9rem; color: var(--text-dim); text-align: center; margin-top: 8px; }
.table-wrap { overflow-x: auto; }
table { border-collapse: collapse; width: 100%; margin: 16px 0; font-size: 0.95rem; }
th, td { border: 1px solid var(--border); padding: 8px 10px; text-align: left; vertical-align: top; }
th { background: var(--raised); }
.callout {
  border-left: 4px solid var(--primary);
  background: var(--raised);
  padding: 12px 16px;
  margin: 24px 0;
}
.callout p { margin: 0; }

/* Infection diagram figures */
.node-ni { fill: var(--node-ni); stroke: var(--node-ni-stroke); stroke-width: 2.5; }
.node-i { fill: var(--node-i); stroke: var(--node-i-stroke); stroke-width: 2.5; }
.node-label, .rate {
  fill: var(--text);
  font-family: "STIX Two Text", "Cambria Math", "Times New Roman", serif;
  font-style: italic;
}
.node-label { font-size: 30px; }
.rate { font-size: 22px; }
.node-label .sub { font-size: 20px; }
.rate .sub, .rate .sup { font-size: 15px; }
@media (max-width: 600px) {
  /* Wide diagrams shrink to the screen: keep their labels readable */
  .figure-wide .rate { font-size: 27px; }
  .figure-wide .rate .sub, .figure-wide .rate .sup { font-size: 19px; }
}
.arrow-new { stroke: var(--arrow-new); stroke-width: 2.5; stroke-dasharray: 7 6; fill: none; }
.arrow-transfer { stroke: var(--arrow-transfer); stroke-width: 2.5; fill: none; }
.arrow-outs { stroke: var(--arrow-outs); stroke-width: 2.5; fill: none; }
.head-new { fill: var(--arrow-new); }
.head-transfer { fill: var(--arrow-transfer); }
.head-outs { fill: var(--arrow-outs); }

.site-footer {
  max-width: 46rem;
  margin: 0 auto;
  padding: 24px 16px 40px;
  border-top: 1px solid var(--border);
  color: var(--text-dim);
  font-size: 0.9rem;
}
.site-footer p { margin: 0 0 6px; }