/* ============================================================
   SciRecast — design system
   World: a lab's graph paper. Three layers of the architecture take
   three inks: the engine is amber, the support layer is blue, the
   product layer is magenta-free -- magenta is kept for what has to
   stop the reader (a warning, a gate that failed).
   All colors token-routed, 3-state theme (system / light / dark).
   ============================================================ */

:root {
  /* ---- light (complete palette) ---- */
  --bg: #f6f8f9;
  --bg2: #fdfefe;
  --bg3: #eef2f4;
  --ink: #1e2429;
  --ink2: #4b565e;
  --ink3: #7c878f;
  --line: #d5dde2;
  --line2: #c1ccd3;
  --grid: rgba(43, 108, 212, 0.075);
  --grid2: rgba(43, 108, 212, 0.14);

  --cx: #c2570f;          /* amber: the engine, the core layer */
  --cx-ink: #a34a0c;
  --cx-soft: rgba(194, 87, 15, 0.1);
  --cx-soft2: rgba(194, 87, 15, 0.18);
  --cz: #2b6cd4;          /* blue: links, the support layer, the active thing */
  --cz-ink: #2159b1;
  --cz-soft: rgba(43, 108, 212, 0.1);
  --cz-soft2: rgba(43, 108, 212, 0.18);
  --cd: #c9257e;          /* magenta: what must stop the reader */
  --cd-soft: rgba(201, 37, 126, 0.12);
  --good: #2f7d46;
  --good-soft: rgba(47, 125, 70, 0.12);
  --bad: #b3392e;
  --bad-soft: rgba(179, 57, 46, 0.1);

  --sel: rgba(43, 108, 212, 0.22);
  --shadow: 0 1px 2px rgba(30, 36, 41, 0.06), 0 8px 24px -12px rgba(30, 36, 41, 0.14);
  --f-display: "Fraunces", "Iowan Old Style", "Palatino Linotype", Georgia, serif;
  --f-body: "IBM Plex Sans", -apple-system, "Segoe UI", "Helvetica Neue", Arial, sans-serif;
  --f-mono: "IBM Plex Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  color-scheme: light dark;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #14181d;
    --bg2: #1b2127;
    --bg3: #10141a;
    --ink: #e8eaed;
    --ink2: #aeb7be;
    --ink3: #7d868e;
    --line: #2b333b;
    --line2: #39434c;
    --grid: rgba(91, 141, 219, 0.1);
    --grid2: rgba(91, 141, 219, 0.2);
    --cx: #ce7b2b;
    --cx-ink: #e0954a;
    --cx-soft: rgba(206, 123, 43, 0.16);
    --cx-soft2: rgba(206, 123, 43, 0.28);
    --cz: #5b8ddb;
    --cz-ink: #7ba5e6;
    --cz-soft: rgba(91, 141, 219, 0.16);
    --cz-soft2: rgba(91, 141, 219, 0.28);
    --cd: #c74e86;
    --cd-soft: rgba(199, 78, 134, 0.2);
    --good: #58a16c;
    --good-soft: rgba(88, 161, 108, 0.16);
    --bad: #cf6a5f;
    --bad-soft: rgba(207, 106, 95, 0.14);
    --sel: rgba(91, 141, 219, 0.3);
    --shadow: 0 1px 2px rgba(0, 0, 0, 0.4), 0 10px 28px -12px rgba(0, 0, 0, 0.55);
  }
}
:root[data-theme="dark"] {
  --bg: #14181d;
  --bg2: #1b2127;
  --bg3: #10141a;
  --ink: #e8eaed;
  --ink2: #aeb7be;
  --ink3: #7d868e;
  --line: #2b333b;
  --line2: #39434c;
  --grid: rgba(91, 141, 219, 0.1);
  --grid2: rgba(91, 141, 219, 0.2);
  --cx: #ce7b2b;
  --cx-ink: #e0954a;
  --cx-soft: rgba(206, 123, 43, 0.16);
  --cx-soft2: rgba(206, 123, 43, 0.28);
  --cz: #5b8ddb;
  --cz-ink: #7ba5e6;
  --cz-soft: rgba(91, 141, 219, 0.16);
  --cz-soft2: rgba(91, 141, 219, 0.28);
  --cd: #c74e86;
  --cd-soft: rgba(199, 78, 134, 0.2);
  --good: #58a16c;
  --good-soft: rgba(88, 161, 108, 0.16);
  --bad: #cf6a5f;
  --bad-soft: rgba(207, 106, 95, 0.14);
  --sel: rgba(91, 141, 219, 0.3);
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.4), 0 10px 28px -12px rgba(0, 0, 0, 0.55);
}

/* ---------- base ---------- */
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } }
body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--f-body);
  font-size: 16.5px;
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}
h1, h2, h3, h4 { font-family: var(--f-display); line-height: 1.25; text-wrap: balance; margin: 0; }
p { margin: 0 0 1.1em; }
a { color: var(--cz-ink); text-decoration-thickness: 1px; text-underline-offset: 2.5px; }
a:hover { color: var(--cz); }
strong { font-weight: 600; }
::selection { background: var(--sel); }
:focus-visible { outline: 2px solid var(--cz); outline-offset: 2px; border-radius: 2px; }
button { font: inherit; color: inherit; }
img, canvas, svg { max-width: 100%; }
hr { border: 0; border-top: 1px solid var(--line); margin: 2.4em 0; }

.mono, code, kbd { font-family: var(--f-mono); }
code {
  background: var(--bg3);
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: 0.06em 0.35em;
  font-size: 0.86em;
}
sub, sup { line-height: 0; }

/* ---------- top bar ---------- */
.topbar {
  position: sticky;
  top: 0;
  z-index: 50;
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 9px 18px;
  background: color-mix(in srgb, var(--bg) 86%, transparent);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--line);
}
.topbar .brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-family: var(--f-display);
  font-weight: 600;
  font-size: 15px;
  white-space: nowrap;
  color: var(--ink);
  text-decoration: none;
}
.topbar .brand svg { display: block; }
.topbar .spacer { flex: 1; }
.topbar .topnav { display: flex; gap: 2px; }
.topbar .topnav a {
  text-decoration: none;
  color: var(--ink2);
  font-size: 13.5px;
  font-weight: 500;
  padding: 4px 10px;
  border-radius: 7px;
}
.topbar .topnav a:hover { background: var(--bg3); color: var(--ink); }
.topbar .topnav a.active { color: var(--cz-ink); background: var(--cz-soft); }
.topbar .aux { display: flex; gap: 8px; align-items: center; }
.topbar .aux a {
  text-decoration: none;
  color: var(--ink2);
  font-size: 12.5px;
  font-family: var(--f-mono);
  border: 1px solid var(--line2);
  border-radius: 999px;
  padding: 3px 11px;
  background: var(--bg2);
  white-space: nowrap;
}
.topbar .aux a:hover { border-color: var(--ink3); color: var(--ink); }
.progress-track {
  position: absolute;
  left: 0; right: 0; bottom: -1px;
  height: 2px;
  background: transparent;
}
.progress-bar { height: 100%; width: 0; background: linear-gradient(90deg, var(--cz), var(--cx)); }

.theme-switch {
  display: inline-flex;
  border: 1px solid var(--line2);
  border-radius: 999px;
  overflow: hidden;
  background: var(--bg2);
}
.theme-switch button {
  border: 0;
  background: transparent;
  padding: 4px 11px;
  font-size: 12.5px;
  font-weight: 600;
  cursor: pointer;
  color: var(--ink3);
}
.theme-switch button[aria-pressed="true"] { background: var(--ink); color: var(--bg); }

@media (max-width: 760px) {
  .topbar .topnav, .topbar .aux { display: none; }
}

/* ---------- layout ---------- */
.layout {
  display: grid;
  grid-template-columns: 236px minmax(0, 1fr);
  gap: 24px;
  max-width: 1180px;
  margin: 0 auto;
  padding: 0 20px;
}
.rail {
  position: sticky;
  top: 64px;
  align-self: start;
  max-height: calc(100vh - 84px);
  overflow-y: auto;
  padding: 22px 4px 30px 0;
  font-size: 13.5px;
  scrollbar-width: thin;
}
.rail .rail-title {
  font-size: 11px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink3);
  margin: 0 0 10px 10px;
  font-weight: 600;
}
.rail a {
  display: block;
  padding: 5px 10px;
  color: var(--ink2);
  text-decoration: none;
  border-left: 2px solid transparent;
  border-radius: 0 6px 6px 0;
  line-height: 1.45;
}
.rail a .n { font-family: var(--f-mono); font-size: 11px; color: var(--ink3); margin-right: 7px; }
.rail a:hover { background: var(--bg3); color: var(--ink); }
.rail a.active { border-left-color: var(--cz); color: var(--ink); background: var(--cz-soft); }
.rail a.sub { padding-left: 26px; font-size: 12.5px; }
.rail a.sub.active { border-left-color: var(--cx); background: var(--cx-soft); }
.rail .rail-gap { height: 14px; }
main { min-width: 0; padding-bottom: 40px; }

@media (max-width: 1020px) {
  .layout { grid-template-columns: minmax(0, 1fr); }
  .rail { display: none; }
}

/* mobile TOC */
.toc-mobile {
  margin: 18px 0 0;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--bg2);
  overflow: hidden;
}
.toc-mobile summary {
  cursor: pointer;
  padding: 11px 16px;
  font-weight: 600;
  font-size: 14px;
  list-style: none;
  display: flex;
  align-items: center;
  gap: 8px;
}
.toc-mobile summary::-webkit-details-marker { display: none; }
.toc-mobile summary::after { content: "▾"; margin-left: auto; color: var(--ink3); }
.toc-mobile[open] summary::after { content: "▴"; }
.toc-mobile nav { padding: 4px 10px 12px; display: grid; gap: 2px; }
.toc-mobile nav a { text-decoration: none; color: var(--ink2); padding: 6px 8px; border-radius: 6px; font-size: 14px; }
.toc-mobile nav a:hover { background: var(--bg3); }
.toc-mobile nav a .n { font-family: var(--f-mono); font-size: 11px; color: var(--ink3); margin-right: 8px; }
@media (min-width: 1021px) { .toc-mobile { display: none; } }

/* ---------- hero ---------- */
.hero {
  position: relative;
  overflow: hidden;
  border-bottom: 1px solid var(--line);
  background:
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: 26px 26px;
  background-color: var(--bg);
}
.hero-inner {
  position: relative;
  max-width: 880px;
  margin: 0 auto;
  padding: 72px 24px 64px;
  text-align: left;
}
.hero .eyebrow, .ch-head .ch-no {
  font-family: var(--f-mono);
  font-size: 12.5px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--cz-ink);
  margin-bottom: 14px;
  font-weight: 600;
}
.hero h1 {
  font-size: clamp(34px, 6vw, 58px);
  font-weight: 600;
  letter-spacing: -0.01em;
}
.hero h1 .accent { color: var(--cz-ink); font-style: italic; }
.hero .lede {
  max-width: 60ch;
  margin-top: 20px;
  font-size: clamp(16px, 2vw, 18.5px);
  color: var(--ink2);
  line-height: 1.8;
}
.hero .promise {
  display: inline-flex;
  align-items: baseline;
  gap: 10px;
  margin-top: 26px;
  padding: 10px 16px;
  border: 1px solid var(--line2);
  border-left: 3px solid var(--cx);
  background: var(--bg2);
  border-radius: 8px;
  font-size: 14.5px;
  box-shadow: var(--shadow);
}
.hero .promise .mono { color: var(--cx-ink); font-weight: 600; }
.hero .cta-row { margin-top: 30px; display: flex; flex-wrap: wrap; gap: 12px; align-items: center; }
.hero-figure { margin: 34px 0 0; max-width: 880px; }
.hero-figure svg { display: block; width: 100%; height: auto; }
@media (max-width: 640px) { .hero-figure { display: none; } }

/* a page that is not the front page opens with a chapter head instead */
.ch-head { margin: 34px 0 6px; }
.ch-head .ch-no { font-size: 13px; letter-spacing: 0.14em; margin-bottom: 0; }
.ch-head h1, .ch-head h2 {
  font-size: clamp(30px, 5vw, 44px);
  font-weight: 600;
  margin-top: 8px;
  padding-bottom: 14px;
  border-bottom: 2px solid var(--ink);
  letter-spacing: -0.01em;
}
.ch-head .ch-lede { color: var(--ink2); margin-top: 14px; max-width: 68ch; font-size: 1.05em; }

.btn {
  display: inline-block;
  border: 1px solid var(--line2);
  background: var(--bg2);
  color: var(--ink);
  border-radius: 8px;
  padding: 6px 14px;
  font-size: 13.5px;
  font-weight: 500;
  cursor: pointer;
  text-decoration: none;
  transition: transform 0.06s, border-color 0.12s, background 0.12s;
}
.btn:hover { border-color: var(--ink3); color: var(--ink); }
.btn:active { transform: translateY(1px); }
.btn.primary { background: var(--ink); border-color: var(--ink); color: var(--bg); }
.btn.primary:hover { opacity: 0.92; color: var(--bg); }

/* ---------- chapters ---------- */
.chapter { padding-top: 34px; scroll-margin-top: 56px; }
.chapter h3 {
  font-family: var(--f-display);
  font-size: clamp(22px, 3vw, 27px);
  font-weight: 600;
  margin: 2.2em 0 0.7em;
  scroll-margin-top: 72px;
}
.chapter h3 .sec-no {
  font-family: var(--f-mono);
  font-size: 13px;
  color: var(--cz-ink);
  letter-spacing: 0.14em;
  margin-right: 12px;
  font-weight: 600;
  vertical-align: 0.3em;
}
.formula {
  max-width: 70ch;
  margin: 1.3em 0;
  padding: 14px 20px;
  font-family: var(--f-mono);
  font-size: 15.5px;
  line-height: 2;
  background: var(--bg2);
  border: 1px solid var(--line);
  border-radius: 10px;
  overflow-x: auto;
  white-space: nowrap;
}
.formula.center { text-align: center; }
.formula .dim { color: var(--ink3); }

/* ---------- prose ---------- */
.prose { padding-top: 6px; }
.prose > p, .prose > ul, .prose > ol { max-width: 70ch; }
.prose h2 {
  font-size: clamp(24px, 3.6vw, 32px);
  font-weight: 600;
  margin: 2.2em 0 0.5em;
  padding-bottom: 12px;
  border-bottom: 2px solid var(--ink);
  scroll-margin-top: 72px;
}
.prose h2 .sec-no {
  font-family: var(--f-mono);
  font-size: 13px;
  color: var(--cz-ink);
  letter-spacing: 0.14em;
  margin-right: 12px;
  font-weight: 600;
  vertical-align: 0.35em;
}
.prose h3 {
  font-size: 21.5px;
  font-weight: 600;
  margin: 2.1em 0 0.7em;
  scroll-margin-top: 72px;
}
.prose h4 { font-size: 17px; margin: 1.6em 0 0.6em; scroll-margin-top: 72px; }
.prose ul, .prose ol { padding-left: 1.4em; }
.prose li { margin: 0.25em 0; }
.prose blockquote {
  max-width: 70ch;
  margin: 1.4em 0;
  padding: 12px 18px;
  border: 1px solid var(--line);
  border-left: 3px solid var(--cz);
  border-radius: 10px;
  background: var(--bg2);
  color: var(--ink2);
}
.prose blockquote p:last-child { margin-bottom: 0; }
.prose em { font-style: italic; }
.prose > p > em:only-child, .prose p.caption { color: var(--ink2); font-size: 0.93em; }

/* callouts, written in markdown as a blockquote whose first word is the tag */
.note {
  max-width: 70ch;
  margin: 1.4em 0;
  padding: 14px 18px;
  border: 1px solid var(--line);
  border-radius: 10px;
  background: var(--bg2);
  font-size: 0.97em;
}
.note .note-tag {
  display: inline-block;
  font-family: var(--f-mono);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  margin-bottom: 6px;
}
.note-key { border-left: 3px solid var(--cz); }
.note-key .note-tag { color: var(--cz-ink); }
.note-honest { border-left: 3px solid var(--cx); }
.note-honest .note-tag { color: var(--cx-ink); }
.note-warn { border-left: 3px solid var(--cd); }
.note-warn .note-tag { color: var(--cd); }
.note p:last-child { margin-bottom: 0; }

/* code blocks (kramdown + rouge) */
.prose pre {
  margin: 1.3em 0;
  padding: 14px 18px;
  font-family: var(--f-mono);
  font-size: 13.5px;
  line-height: 1.65;
  background: var(--bg2);
  border: 1px solid var(--line);
  border-radius: 10px;
  overflow-x: auto;
  color: var(--ink);
}
.prose pre code { background: transparent; border: 0; padding: 0; font-size: inherit; }

/* tables */
.prose table, .table-wrap table {
  border-collapse: collapse;
  width: 100%;
  font-size: 14.5px;
  margin: 1.4em 0;
  background: var(--bg2);
  border: 1px solid var(--line);
  border-radius: 10px;
  overflow: hidden;
}
.prose th, .prose td {
  text-align: left;
  padding: 9px 12px;
  border-bottom: 1px solid var(--line);
  vertical-align: top;
}
.prose th {
  font-size: 12px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--ink3);
  font-family: var(--f-body);
  font-weight: 600;
  background: var(--bg3);
}
.prose tr:last-child td { border-bottom: 0; }
.prose td:first-child { white-space: normal; }
.prose th[scope="row"] {
  font-size: inherit;
  letter-spacing: 0;
  text-transform: none;
  color: var(--ink);
  font-weight: 600;
  background: transparent;
  width: 20%;
}
.prose .route td:first-child, .prose .route th:first-child { width: 34%; font-weight: 600; }
.prose .compare, .prose .route { table-layout: fixed; min-width: 560px; }
.table-wrap { overflow-x: auto; margin: 1.4em 0; }
.table-wrap table { margin: 0; }
/* a table whose header row is empty (markdown "| | |") drops it */
.prose thead.empty { display: none; }

/* ---------- chapter nav / footer ---------- */
.ch-nav {
  display: flex;
  justify-content: space-between;
  gap: 14px;
  margin: 3em 0 1em;
  padding-top: 18px;
  border-top: 1px solid var(--line);
}
.ch-nav a {
  text-decoration: none;
  color: var(--ink2);
  font-size: 14px;
  max-width: 46%;
}
.ch-nav a.next { text-align: right; margin-left: auto; }
.ch-nav a.prev { margin-right: auto; }
.ch-nav a b { display: block; color: var(--ink); font-size: 15px; margin-top: 2px; font-family: var(--f-display); }
.ch-nav a:hover b { color: var(--cz-ink); }

.footer {
  border-top: 1px solid var(--line);
  margin-top: 30px;
  padding: 26px 20px 42px;
  color: var(--ink3);
  font-size: 13.5px;
  text-align: center;
}
.footer a { color: var(--ink2); }
.footer p { margin: 0 0 0.4em; }

.muted { color: var(--ink3); }
.small { font-size: 0.88em; }
.center { text-align: center; }

@media (max-width: 640px) {
  body { font-size: 15.5px; }
  .hero-inner { padding: 48px 18px 44px; }
  .layout { padding: 0 14px; }
}
@media (prefers-reduced-motion: reduce) {
  * { animation-duration: 0.001s !important; transition-duration: 0.001s !important; }
}