:root {
  --paper: #f3efe6;
  --sheet: #faf8f3;
  --ink: #1c1915;
  --ink-soft: #3f3a33;
  --muted: #746d62;
  --line: #e0d8ca;
  --line-strong: #cfc4b2;
  --binding: #1d3c33;
  --binding-soft: #e4efe8;
  --rust: #8d341f;
  --rust-soft: #f6ebe4;
  --gold: #8a5a12;
  --shadow: 0 18px 40px rgba(48, 36, 18, 0.06);
  --serif: "Newsreader", "Iowan Old Style", Palatino, "Palatino Linotype", serif;
  --display: "Fraunces", "Iowan Old Style", Palatino, serif;
  --sans: "Outfit", "Avenir Next", "Segoe UI", sans-serif;
  --mono: "IBM Plex Mono", ui-monospace, monospace;
  --measure: 42rem;
  --sidebar: 16.5rem;
  color-scheme: light;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background:
    radial-gradient(1200px 500px at 10% -10%, rgba(29, 60, 51, 0.05), transparent 50%),
    var(--paper);
  color: var(--ink);
  font-family: var(--serif);
  font-size: 1.125rem;
  line-height: 1.55;
  font-optical-sizing: auto;
}

::selection {
  background: #d7e7dc;
  color: var(--ink);
}

a { color: inherit; }

img { max-width: 100%; }

.skip {
  position: absolute;
  left: 1rem;
  top: -4rem;
  background: var(--ink);
  color: var(--sheet);
  padding: 0.5rem 0.75rem;
  z-index: 5;
}

.skip:focus { top: 1rem; }

.top {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem 1.25rem;
  padding: 0.9rem 1.5rem;
  border-bottom: 1px solid var(--line);
  background: rgba(243, 239, 230, 0.92);
  position: sticky;
  top: 0;
  z-index: 4;
  backdrop-filter: blur(10px);
}

.brand {
  display: flex;
  flex-direction: column;
  text-decoration: none;
  min-width: max-content;
}

.brand-kicker {
  font-family: var(--sans);
  font-size: 0.68rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--muted);
}

.brand-name {
  font-family: var(--display);
  font-weight: 560;
  font-size: 1.25rem;
  letter-spacing: -0.02em;
  line-height: 1.1;
}

.subject-nav {
  display: flex;
  flex: 1 1 28rem;
  flex-wrap: wrap;
  justify-content: flex-end;
  gap: 0.15rem;
  min-width: 0;
}

.subject-nav a {
  font-family: var(--sans);
  font-size: 0.84rem;
  text-decoration: none;
  color: var(--ink-soft);
  padding: 0.35rem 0.6rem;
  border-radius: 999px;
  white-space: nowrap;
}

.subject-nav a:hover { background: rgba(28, 25, 21, 0.05); }

.subject-nav a[aria-current="page"] {
  background: var(--binding);
  color: #f4f7f5;
}

.shell {
  width: min(1120px, calc(100% - 2.5rem));
  margin: 0 auto;
  padding: 2.5rem 0 5rem;
}

.shell.article {
  width: min(46rem, calc(100% - 2.5rem));
}

.home-lead {
  display: grid;
  grid-template-columns: minmax(0, 1.4fr) minmax(16rem, 0.7fr);
  gap: 3rem;
  align-items: end;
  margin-bottom: 2.75rem;
  padding-bottom: 2rem;
  border-bottom: 1px solid var(--line);
}

h1 {
  font-family: var(--display);
  font-weight: 560;
  font-size: clamp(2.6rem, 6vw, 4.4rem);
  letter-spacing: -0.035em;
  line-height: 0.96;
  margin: 0 0 0.8rem;
}

.lede {
  margin: 0;
  max-width: 38rem;
  font-size: 1.22rem;
  color: var(--ink-soft);
}

.home-stat {
  font-family: var(--sans);
  color: var(--muted);
  font-size: 0.92rem;
  border-left: 2px solid var(--binding);
  padding: 0.2rem 0 0.2rem 1rem;
}

.home-stat strong {
  display: block;
  color: var(--ink);
  font-weight: 560;
  font-size: 1.05rem;
  margin-bottom: 0.25rem;
}

.shelf {
  list-style: none;
  margin: 0;
  padding: 0;
}

.shelf li { border-bottom: 1px solid var(--line); }

.shelf a {
  display: grid;
  grid-template-columns: 3rem minmax(0, 1fr) auto;
  gap: 0.75rem 1.25rem;
  align-items: baseline;
  text-decoration: none;
  padding: 1.15rem 0.2rem;
}

.shelf a:hover .shelf-title { color: var(--binding); }

.shelf-num {
  font-family: var(--mono);
  font-size: 0.82rem;
  color: var(--muted);
}

.shelf-title {
  font-family: var(--display);
  font-size: 1.65rem;
  letter-spacing: -0.03em;
  line-height: 1.15;
}

.shelf-scope {
  grid-column: 2;
  color: var(--muted);
  font-size: 1.02rem;
  margin-top: -0.15rem;
}

.shelf-status {
  font-family: var(--sans);
  font-size: 0.75rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
}

.shelf-status.ready {
  color: var(--binding);
}

.layout {
  display: grid;
  grid-template-columns: var(--sidebar) minmax(0, var(--measure));
  gap: 3rem;
  align-items: start;
}

.toc {
  position: sticky;
  top: 5.2rem;
  max-height: calc(100vh - 6.5rem);
  overflow: auto;
  padding-right: 0.5rem;
}

.toc-label {
  font-family: var(--sans);
  font-size: 0.7rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--muted);
  margin: 0 0 0.7rem;
}

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

.toc a {
  display: block;
  text-decoration: none;
  font-family: var(--sans);
  font-size: 0.86rem;
  color: var(--ink-soft);
  padding: 0.22rem 0 0.22rem 0.7rem;
  border-left: 2px solid transparent;
  line-height: 1.35;
}

.toc a:hover,
.toc a.active {
  color: var(--ink);
  border-left-color: var(--binding);
}

.toc .group {
  margin: 0.85rem 0 0.3rem;
  font-family: var(--sans);
  font-size: 0.68rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--muted);
}

.article h1 {
  font-size: clamp(2.4rem, 5vw, 3.5rem);
  margin-bottom: 0.4rem;
}

.kicker {
  font-family: var(--sans);
  font-size: 0.75rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--binding);
  margin: 0 0 0.6rem;
}

.source {
  margin: 0 0 1.6rem;
  color: var(--muted);
  font-size: 1.02rem;
}

.prose p { margin: 0 0 1rem; }

.prose strong { font-weight: 560; }

.assembly {
  margin: 0 0 1.6rem;
  padding: 1rem 1.1rem 0.4rem;
  background: var(--sheet);
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
}

.assembly-kicker {
  font-family: var(--sans);
  font-size: 0.7rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--muted);
  margin: 0 0 0.6rem;
}

.assembly ol {
  list-style: none;
  margin: 0;
  padding: 0;
}

.assembly li {
  display: grid;
  grid-template-columns: 9.5rem minmax(0, 1fr);
  gap: 1rem;
  align-items: baseline;
  padding: 0.7rem 0;
  border-top: 1px solid var(--line);
}

.assembly li strong {
  font-family: var(--sans);
  font-weight: 560;
  font-size: 0.95rem;
}

.callout {
  margin: 1.2rem 0 1.6rem;
  padding: 0.9rem 1rem;
  background: var(--rust-soft);
  border-left: 3px solid var(--rust);
}

.callout p { margin: 0; }

h2 {
  font-family: var(--display);
  font-weight: 560;
  font-size: 1.85rem;
  letter-spacing: -0.03em;
  margin: 2.4rem 0 0.8rem;
}

.decoder {
  width: 100%;
  border-collapse: collapse;
  font-size: 1.02rem;
  margin: 0.4rem 0 0.4rem;
}

.decoder th,
.decoder td {
  text-align: left;
  vertical-align: baseline;
  padding: 0.55rem 0.7rem 0.55rem 0;
  border-bottom: 1px solid var(--line);
}

.decoder th {
  font-family: var(--sans);
  font-size: 0.72rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--muted);
  font-weight: 500;
}

.decoder td:first-child { width: 38%; }

.formula {
  margin: 2.2rem 0 0;
  padding-top: 0.2rem;
  scroll-margin-top: 5.5rem;
}

.formula-head {
  display: flex;
  align-items: baseline;
  gap: 0.8rem;
  margin-bottom: 0.7rem;
}

.formula-num {
  font-family: var(--mono);
  font-size: 0.82rem;
  color: var(--binding);
}

.formula h2 {
  margin: 0;
  font-size: 1.55rem;
}

.symbols {
  background: var(--sheet);
  border: 1px solid var(--line);
  border-left: 3px solid var(--binding);
  padding: 0.35rem 1rem;
  overflow-x: auto;
  margin-bottom: 0.3rem;
}

.symbols .katex-display { margin: 0.7rem 0; }

.parts {
  margin: 0.4rem 0 0;
}

.parts > div {
  display: grid;
  grid-template-columns: 7.2rem minmax(0, 1fr);
  gap: 0.8rem;
  padding: 0.75rem 0;
  border-bottom: 1px solid var(--line);
}

.parts dt {
  font-family: var(--sans);
  font-size: 0.72rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--muted);
  padding-top: 0.28rem;
}

.parts dd { margin: 0; }

.parts .fail {
  background: var(--rust-soft);
  border-bottom: 0;
  margin-top: 0.35rem;
  padding: 0.8rem 0.85rem;
}

.parts .fail dt { color: var(--rust); }

.patterns {
  list-style: none;
  margin: 0;
  padding: 0;
}

.patterns li {
  padding: 1rem 0;
  border-top: 1px solid var(--line);
}

.patterns h3 {
  font-family: var(--sans);
  font-size: 1rem;
  font-weight: 560;
  margin: 0 0 0.3rem;
}

.patterns p { margin: 0; }

.closing {
  margin-top: 1.4rem;
  padding-top: 1rem;
  border-top: 1px solid var(--line-strong);
}

.empty {
  margin-top: 1.5rem;
  padding: 1.3rem 1.2rem 1.1rem;
  background: var(--sheet);
  border: 1px dashed var(--line-strong);
}

.empty h2 {
  margin: 0 0 0.4rem;
  font-size: 1.4rem;
}

.empty p { margin: 0 0 0.8rem; color: var(--ink-soft); }

.scope-list {
  margin: 0;
  padding: 0;
  list-style: none;
}

.scope-list li {
  font-family: var(--sans);
  padding: 0.35rem 0;
  border-top: 1px solid var(--line);
}

code, .tick {
  font-family: var(--mono);
  font-size: 0.86em;
  background: rgba(28, 25, 21, 0.05);
  padding: 0.05em 0.3em;
}

.katex { font-size: 1.05em; }

@media (max-width: 860px) {
  .home-lead,
  .layout,
  .assembly li,
  .parts > div {
    grid-template-columns: 1fr;
  }

  .shelf a {
    grid-template-columns: auto minmax(0, 1fr);
    grid-template-areas:
      "num title"
      "num scope"
      "status status";
  }

  .shelf-num { grid-area: num; }
  .shelf-title { grid-area: title; }
  .shelf-scope { grid-area: scope; grid-column: auto; }
  .shelf-status { grid-area: status; }

  .toc {
    position: static;
    max-height: 14rem;
    border: 1px solid var(--line);
    background: var(--sheet);
    padding: 0.8rem 0.9rem;
    margin-bottom: 1.5rem;
  }

  .top { position: static; align-items: flex-start; }
  .subject-nav { justify-content: flex-start; }

  .shell { width: min(1120px, calc(100% - 1.5rem)); }
}

@media print {
  .top, .toc, .skip { display: none; }
  body { background: white; }
  .layout { display: block; }
  .formula { break-inside: avoid; }
}