:root {
  --paper: #f4f7f8;
  --paper-strong: #ffffff;
  --ink: #15232b;
  --muted: #53646d;
  --grid: #ccd9de;
  --grid-soft: rgba(76, 116, 134, 0.09);
  --cobalt: #1956d1;
  --cobalt-deep: #113b91;
  --sulfur: #e8f23a;
  --terminal: #102830;
  --terminal-line: #31515b;
  --terminal-copy: #eaf3f4;
  --error: #ad2c35;
  --rail: 264px;
  --measure: 72ch;
  --section: clamp(5rem, 9vw, 9rem);
  --ease-out: cubic-bezier(.16, 1, .3, 1);
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: 3rem;
}

body {
  margin: 0;
  color: var(--ink);
  background-color: var(--paper);
  background-image:
    linear-gradient(var(--grid-soft) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid-soft) 1px, transparent 1px);
  background-size: 24px 24px;
  font-family: Aptos, "Segoe UI", "Helvetica Neue", Arial, sans-serif;
  font-size: 16px;
  line-height: 1.65;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
}

body.nav-open { overflow: hidden; }

a { color: var(--cobalt-deep); text-underline-offset: 3px; }
a:hover { color: var(--cobalt); }
button, summary { font: inherit; }
button { color: inherit; }
code, pre, samp {
  font-family: ui-monospace, SFMono-Regular, Consolas, "Liberation Mono", monospace;
  font-variant-ligatures: none;
}

code {
  font-size: .9em;
  padding: .08em .25em;
  color: var(--cobalt-deep);
  background: rgba(25, 86, 209, .07);
}

h1, h2, h3, p { margin-top: 0; }
h2, h3 { text-wrap: balance; }
h2 {
  margin-bottom: 1.25rem;
  max-width: 19ch;
  font-family: "Arial Narrow", "Aptos Narrow", "Helvetica Neue", Arial, sans-serif;
  font-size: clamp(2.7rem, 5vw, 5.7rem);
  font-stretch: condensed;
  font-weight: 800;
  letter-spacing: -.035em;
  line-height: .94;
}

h3 {
  margin: 2.75rem 0 .75rem;
  font-size: clamp(1.35rem, 2.4vw, 2rem);
  line-height: 1.15;
  letter-spacing: -.02em;
}

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

:focus-visible {
  outline: 3px solid var(--cobalt);
  outline-offset: 3px;
}

.skip-link {
  position: fixed;
  z-index: 100;
  top: .75rem;
  left: .75rem;
  padding: .7rem 1rem;
  color: var(--paper-strong);
  background: var(--ink);
  transform: translateY(-160%);
  transition: transform .18s var(--ease-out);
}
.skip-link:focus { transform: translateY(0); }

.course-rail {
  position: fixed;
  z-index: 30;
  inset: 0 auto 0 0;
  display: flex;
  width: var(--rail);
  flex-direction: column;
  border-right: 1px solid var(--ink);
  background: rgba(244, 247, 248, .97);
}

.rail-brand a {
  display: flex;
  min-height: 92px;
  gap: .9rem;
  align-items: center;
  padding: 1.25rem;
  border-bottom: 1px solid var(--grid);
  color: var(--ink);
  text-decoration: none;
}

.rail-brand strong {
  display: block;
  font: 800 1.05rem/1 "Arial Narrow", "Aptos Narrow", sans-serif;
  letter-spacing: .04em;
}

.rail-brand small {
  display: block;
  margin-top: .35rem;
  color: var(--muted);
  font: 600 .64rem/1.3 ui-monospace, monospace;
  text-transform: uppercase;
}

.rail-mark {
  display: grid;
  width: 34px;
  height: 34px;
  place-items: center;
  border: 1px solid var(--ink);
}
.rail-mark::before, .rail-mark::after, .rail-mark i::before, .rail-mark i::after { content: ""; position: absolute; background: var(--cobalt); }
.rail-mark { position: relative; }
.rail-mark::before { width: 20px; height: 1px; }
.rail-mark::after { width: 1px; height: 20px; }
.rail-mark i { width: 7px; height: 7px; border: 2px solid var(--cobalt); border-radius: 50%; background: var(--paper); z-index: 1; }

.rail-progress {
  padding: 1rem 1.25rem 1.1rem;
  border-bottom: 1px solid var(--grid);
  font: 700 .64rem/1 ui-monospace, monospace;
}
.rail-progress > div:first-child { display: flex; justify-content: space-between; }
.rail-progress output { color: var(--cobalt); }
.progress-track { height: 4px; margin-top: .75rem; background: var(--grid); }
.progress-track i { display: block; width: 100%; height: 100%; background: var(--cobalt); transform: scaleX(0); transform-origin: left; transition: transform .15s linear; }

.rail-nav {
  position: relative;
  flex: 1;
  overflow-y: auto;
  padding: .7rem 0;
  scrollbar-width: thin;
}
.rail-nav::before {
  content: "";
  position: absolute;
  top: 1.7rem;
  bottom: 1.7rem;
  left: 2rem;
  width: 1px;
  background: var(--grid);
}
.rail-nav a {
  position: relative;
  display: grid;
  grid-template-columns: 2.9rem 1fr;
  align-items: center;
  min-height: 42px;
  padding: .35rem 1rem .35rem 1rem;
  color: var(--ink);
  font-size: .8rem;
  line-height: 1.1;
  text-decoration: none;
}
.rail-nav a::before {
  content: "";
  position: absolute;
  left: 1.77rem;
  width: 7px;
  height: 7px;
  border: 1px solid var(--cobalt);
  border-radius: 50%;
  background: var(--paper);
}
.rail-nav a b { color: var(--muted); font: 600 .65rem/1 ui-monospace, monospace; }
.rail-nav a span { font-weight: 650; }
.rail-nav a:hover { background: rgba(25, 86, 209, .07); }
.rail-nav a.active { color: white; background: var(--cobalt); }
.rail-nav a.active b { color: white; }
.rail-nav a.active::before { left: 1.55rem; width: 14px; height: 14px; border: 3px solid var(--paper); background: var(--sulfur); box-shadow: 0 0 0 1px var(--ink); }

.rail-foot {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: .9rem 1.25rem;
  border-top: 1px solid var(--grid);
  font: 650 .62rem/1 ui-monospace, monospace;
}
.rail-foot a { text-decoration: none; }
.rail-foot span { color: var(--muted); }

.mobile-bar { display: none; }

main { margin-left: var(--rail); overflow: clip; }

.hero {
  position: relative;
  display: grid;
  min-height: 100svh;
  grid-template-rows: auto 1fr auto;
  border-bottom: 1px solid var(--ink);
  background: rgba(244, 247, 248, .68);
}
.hero::before {
  content: "0   24   48   72   96   120   144   168   192";
  position: absolute;
  inset: .5rem 2rem auto 2rem;
  color: #819098;
  font: 500 .58rem/1 ui-monospace, monospace;
  letter-spacing: clamp(.4rem, 2.1vw, 2.3rem);
  white-space: nowrap;
  overflow: hidden;
}
.hero-heading {
  display: grid;
  grid-template-columns: minmax(320px, .9fr) minmax(290px, 1fr) minmax(220px, .6fr);
  gap: 2rem;
  align-items: center;
  padding: clamp(4.5rem, 9vw, 8rem) clamp(2rem, 5vw, 5.5rem) 2.2rem;
  border-bottom: 1px solid var(--grid);
}
.hero-heading h1 {
  margin: 0;
  font: 900 clamp(4.5rem, 9vw, 6rem)/.78 "Arial Narrow", "Aptos Narrow", "Helvetica Neue", sans-serif;
  letter-spacing: -.035em;
}
.hero-heading > p {
  margin: 0;
  font: 500 clamp(1.35rem, 2.8vw, 2.6rem)/1.15 ui-monospace, monospace;
  letter-spacing: -.035em;
}
.hero-note {
  position: relative;
  padding: 1rem 1.15rem;
  border: 1px solid var(--grid);
  background: rgba(255,255,255,.42);
}
.hero-note::before, .hero-note::after { content: ""; position: absolute; width: 11px; height: 11px; }
.hero-note::before { top: -1px; left: -1px; border-top: 2px solid var(--cobalt); border-left: 2px solid var(--cobalt); }
.hero-note::after { right: -1px; bottom: -1px; border-right: 2px solid var(--cobalt); border-bottom: 2px solid var(--cobalt); }
.hero-note span, .instrument-label, .chapter-kicker, .setup-strip span, .margin-note > span, .feature-plate .plate-copy > span, .checker-band > span, .checkpoint > span, .server-strip span, .run-web > div span, .finish-block > span {
  color: var(--cobalt-deep);
  font: 750 .68rem/1.2 ui-monospace, monospace;
  letter-spacing: .08em;
}
.hero-note p { margin: .6rem 0 0; font: .78rem/1.55 ui-monospace, monospace; }

.hero-thesis {
  display: grid;
  grid-template-columns: minmax(390px, .86fr) minmax(480px, 1.14fr);
  gap: clamp(1.5rem, 3vw, 3.5rem);
  align-items: stretch;
  padding: clamp(2rem, 5vw, 5rem) clamp(2rem, 5vw, 5.5rem);
}
.state-instrument {
  position: relative;
  min-height: 410px;
  padding: 1.25rem;
  border: 1px solid var(--grid);
  background: rgba(255,255,255,.38);
}
.instrument-label { display: flex; justify-content: space-between; }
.instrument-label b { color: var(--muted); font-weight: 600; }
.instrument-thesis {
  position: absolute;
  z-index: 2;
  top: 4.25rem;
  left: 1.25rem;
  margin: 0;
  max-width: 43%;
  font: 850 clamp(1.75rem, 2.7vw, 3rem)/.92 "Arial Narrow", "Aptos Narrow", sans-serif;
  letter-spacing: -.03em;
}
.state-stack {
  position: absolute;
  z-index: 2;
  top: 4.25rem;
  right: 1.25rem;
  display: grid;
  width: min(48%, 240px);
  gap: .65rem;
}
.state-layer { position: relative; padding: 1rem; border: 1px solid var(--cobalt); background: var(--paper-strong); box-shadow: 6px 6px 0 rgba(25,86,209,.12); }
.state-layer span { color: var(--cobalt); font: 750 .7rem/1 ui-monospace, monospace; }
.state-layer code { display: block; padding: 0; margin-top: .65rem; font-size: 1.2rem; background: none; }
.state-layer p { margin: .2rem 0 0; color: var(--muted); font-size: .75rem; }
.state-join { justify-self: center; font: 750 1rem/1 ui-monospace, monospace; }
.trace-svg { position: absolute; inset: auto 1rem 1rem; width: calc(100% - 2rem); height: 43%; overflow: visible; }
.trace-path { fill: none; stroke: var(--cobalt); stroke-width: 4; stroke-linecap: square; stroke-linejoin: miter; stroke-dasharray: 900; stroke-dashoffset: 900; }
.trace-svg circle { fill: var(--paper); stroke: var(--cobalt); stroke-width: 3; }
.trace-svg .trace-end { fill: var(--sulfur); stroke: var(--ink); }
.hero.ready .trace-path { animation: draw-trace 1.7s .2s var(--ease-out) forwards; }
@keyframes draw-trace { to { stroke-dashoffset: 0; } }

.code-instrument {
  position: relative;
  align-self: stretch;
  overflow: hidden;
  border: 1px solid var(--terminal);
  border-radius: 6px;
  background: var(--terminal);
  box-shadow: 9px 10px 0 rgba(17,59,145,.13);
}
.code-toolbar {
  display: flex;
  min-height: 42px;
  justify-content: space-between;
  align-items: center;
  padding: 0 .85rem 0 1rem;
  border-bottom: 1px solid var(--terminal-line);
  color: #a9c6ce;
  background: #0b2027;
  font: 700 .65rem/1 ui-monospace, monospace;
  letter-spacing: .08em;
}
.copy-button {
  min-width: 62px;
  min-height: 44px;
  padding: .42rem .7rem;
  border: 1px solid #76929a;
  border-radius: 2px;
  color: #dfecee;
  background: transparent;
  font: 700 .62rem/1 ui-monospace, monospace;
  letter-spacing: .06em;
  cursor: pointer;
}
.copy-button:hover { color: var(--ink); border-color: var(--sulfur); background: var(--sulfur); }
.copy-button.copied { color: var(--ink); border-color: var(--sulfur); background: var(--sulfur); }
.code-instrument pre {
  min-height: 180px;
  margin: 0;
  padding: clamp(1.2rem, 2.4vw, 2rem);
  overflow: auto;
  color: var(--terminal-copy);
  font-size: clamp(.75rem, 1.15vw, .94rem);
  line-height: 1.7;
  tab-size: 2;
}
.code-instrument pre code { padding: 0; color: inherit; background: none; font-size: inherit; }
.tok-keyword { color: #77a7ff; }
.tok-string { color: #dcea79; }
.tok-number { color: #ffc66d; }
.tok-comment { color: #86a0a8; font-style: italic; }
.hero-code pre { min-height: 320px; }
.code-output {
  display: grid;
  min-height: 50px;
  grid-template-columns: minmax(110px, .24fr) 1fr;
  align-items: center;
  color: var(--ink);
  background: var(--sulfur);
  font: 700 .78rem/1.35 ui-monospace, monospace;
}
.code-output span { align-self: stretch; display: flex; align-items: center; padding: .75rem 1rem; border-right: 1px solid var(--ink); letter-spacing: .07em; }
.code-output samp { padding: .75rem 1rem; font-weight: 650; }
.code-output.multi { align-items: stretch; }
.code-output.multi samp { line-height: 1.65; }

.hero-actions {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1.35rem clamp(2rem, 5vw, 5.5rem);
  border-top: 1px solid var(--grid);
}
.primary-action {
  display: inline-flex;
  gap: 2rem;
  align-items: center;
  justify-content: space-between;
  min-height: 48px;
  padding: .75rem 1rem;
  border: 1px solid var(--ink);
  border-radius: 2px;
  color: var(--ink);
  background: var(--sulfur);
  font: 800 .72rem/1 ui-monospace, monospace;
  letter-spacing: .06em;
  text-decoration: none;
  transition: background .18s ease, color .18s ease, transform .18s var(--ease-out);
}
.primary-action:hover { color: white; background: var(--cobalt); transform: translateY(-2px); }
.hero-actions > p { display: flex; gap: 1rem; margin: 0; align-items: baseline; }
.hero-actions > p strong { font-size: .85rem; }
.hero-actions > p span { color: var(--muted); font-size: .75rem; }

.chapter {
  display: grid;
  grid-template-columns: clamp(110px, 13vw, 185px) minmax(0, 1fr);
  border-bottom: 1px solid var(--ink);
  background: rgba(244, 247, 248, .84);
}
.chapter-marker {
  position: relative;
  padding: var(--section) 1.5rem;
  border-right: 1px solid var(--grid);
}
.chapter-marker::before { content: ""; position: absolute; top: var(--section); right: -5px; width: 9px; height: 9px; border: 1px solid var(--cobalt); border-radius: 50%; background: var(--paper); }
.chapter-marker b {
  position: sticky;
  top: 3rem;
  display: block;
  color: var(--cobalt);
  font: 800 clamp(2.2rem, 5vw, 4.5rem)/1 "Arial Narrow", "Aptos Narrow", sans-serif;
}
.chapter-marker span {
  position: sticky;
  top: 8rem;
  display: block;
  margin-top: .5rem;
  color: var(--muted);
  font: 700 .64rem/1.25 ui-monospace, monospace;
  writing-mode: vertical-rl;
  letter-spacing: .08em;
}
.chapter-body { min-width: 0; padding: var(--section) clamp(2rem, 5vw, 6rem); }
.chapter-header { max-width: 1040px; margin-bottom: clamp(3.5rem, 7vw, 7rem); }
.chapter-header > p:last-child { max-width: var(--measure); margin-bottom: 0; color: #33454e; font-size: clamp(1.05rem, 1.5vw, 1.25rem); }
.chapter-kicker { margin-bottom: 1.5rem; }

.setup-strip, .syntax-board, .types-strip, .persistence-ledger, .dom-api {
  display: grid;
  border-top: 1px solid var(--ink);
  border-left: 1px solid var(--ink);
}
.setup-strip { grid-template-columns: repeat(3, 1fr); margin-bottom: 4.5rem; }
.setup-strip > div, .syntax-board > div, .types-strip > div, .persistence-ledger > div, .dom-api > div { padding: 1rem; border-right: 1px solid var(--ink); border-bottom: 1px solid var(--ink); background: rgba(255,255,255,.48); }
.setup-strip strong { display: block; margin-top: .5rem; font-size: 1.2rem; }

.lab-pair, .lesson-columns {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: clamp(1.5rem, 3vw, 3rem);
  margin: 4rem 0;
  align-items: start;
}
.lab-pair .code-instrument pre { min-height: 168px; }
.lesson-columns.reverse > :first-child { order: 2; }
.lesson-columns.reverse > :last-child { order: 1; }
.lesson-copy { max-width: var(--measure); }
.lesson-copy > h3:first-child { margin-top: 0; }
.lesson-copy p { color: #33454e; }

.reading-grid {
  display: grid;
  grid-template-columns: minmax(0, var(--measure)) minmax(220px, 320px);
  gap: clamp(2rem, 6vw, 6rem);
  margin: 5rem 0;
  align-items: start;
}
.reading-grid h3 { margin-top: 0; }
.margin-note { padding: 1.25rem; border: 1px solid var(--grid); background: rgba(255,255,255,.5); }
.margin-note p { margin: .7rem 0 0; color: var(--muted); font: .8rem/1.6 ui-monospace, monospace; }
.margin-note.warning { border-color: #bc9f14; background: rgba(232,242,58,.12); }

.trace-list { padding: 0; margin: 1.2rem 0; list-style: none; counter-reset: trace; }
.trace-list li { position: relative; padding: .8rem 0 .8rem 3rem; border-top: 1px solid var(--grid); counter-increment: trace; }
.trace-list li::before { content: counter(trace, decimal-leading-zero); position: absolute; top: 1rem; left: .2rem; color: var(--cobalt); font: 700 .7rem/1 ui-monospace, monospace; }
.trace-list li:last-child { border-bottom: 1px solid var(--grid); }

.checkpoint {
  position: relative;
  display: grid;
  grid-template-columns: minmax(140px, .25fr) minmax(240px, .75fr);
  gap: 2rem;
  margin: 5rem 0 1rem;
  padding: 1.4rem 1.5rem;
  border: 1px solid var(--cobalt);
  background: rgba(25,86,209,.04);
}
.checkpoint::before { content: ""; position: absolute; top: -8px; left: 24%; width: 15px; height: 15px; border: 1px solid var(--ink); border-radius: 50%; background: var(--sulfur); }
.checkpoint > p { margin: 0; font-weight: 700; }
.checkpoint details { grid-column: 2; }
.checkpoint summary { color: var(--cobalt-deep); font: 750 .7rem/1 ui-monospace, monospace; cursor: pointer; letter-spacing: .06em; }
.checkpoint details p { margin: 1rem 0 0; color: #33454e; }
.checkpoint.completed::before { background: var(--cobalt); box-shadow: inset 0 0 0 3px var(--sulfur); }

.syntax-board { grid-template-columns: repeat(3, 1fr); margin-bottom: 5rem; }
.syntax-board span, .types-strip span { display: block; margin-bottom: 1.3rem; color: var(--muted); font: 700 .62rem/1 ui-monospace, monospace; letter-spacing: .08em; }
.syntax-board code, .types-strip code { padding: 0; background: none; font-size: .88rem; }
.mini-code { overflow-x: auto; padding: 1rem; border: 1px solid var(--grid); background: var(--paper-strong); }
.mini-code code { padding: 0; background: none; }

.operator-table, .reference-table { width: 100%; overflow-x: auto; margin: 4rem 0; border: 1px solid var(--ink); background: rgba(255,255,255,.48); }
table { width: 100%; border-collapse: collapse; }
th, td { padding: .85rem 1rem; border-right: 1px solid var(--grid); border-bottom: 1px solid var(--grid); text-align: left; vertical-align: top; }
th { color: var(--cobalt-deep); background: rgba(25,86,209,.06); font: 750 .65rem/1 ui-monospace, monospace; letter-spacing: .06em; }
td:first-child { font-weight: 650; }
td code { white-space: nowrap; }

.type-equation {
  display: grid;
  grid-template-columns: 1fr auto 1fr auto 1fr;
  align-items: center;
  gap: 1rem;
  margin: 4rem 0 6rem;
}
.type-equation > div { min-height: 155px; padding: 1.3rem; border: 1px solid var(--ink); background: var(--paper-strong); }
.type-equation b, .type-equation span, .type-equation code { display: block; }
.type-equation b { color: var(--cobalt); font: 800 1.7rem/1 "Arial Narrow", sans-serif; }
.type-equation span { margin: .5rem 0 1.7rem; color: var(--muted); font-size: .8rem; }
.type-equation code { padding: 0; background: none; font-size: .72rem; }
.type-equation > i { font-style: normal; font-size: 2rem; }
.types-strip { grid-template-columns: repeat(5, 1fr); margin: 5rem 0; }
.types-strip small { display: block; margin-top: .5rem; color: var(--muted); }

.feature-plate, .each-lab {
  display: grid;
  grid-template-columns: .72fr 1.28fr;
  gap: clamp(2rem, 5vw, 5rem);
  margin: 6rem 0;
  padding: clamp(2rem, 4vw, 4rem);
  border: 1px solid var(--cobalt);
  background: rgba(25,86,209,.04);
}
.feature-plate h3, .each-lab h3 { margin-top: 1rem; }
.code-instrument.compact pre { min-height: auto; }

.nominal-lab {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: clamp(2rem, 5vw, 5rem);
  margin: 6rem 0 3rem;
  align-items: center;
}
.nominal-diagram { padding: 1.5rem; border: 1px solid var(--ink); background: white; }
.nominal-diagram > span { display: block; color: var(--muted); font: 700 .65rem/1 ui-monospace, monospace; letter-spacing: .08em; }
.nominal-diagram > div { display: grid; grid-template-columns: 1fr auto 1fr; gap: .8rem; align-items: center; margin: 1rem 0 2rem; }
.nominal-diagram > div code { padding: 1rem; border: 1px solid var(--cobalt); background: rgba(25,86,209,.04); text-align: center; }
.nominal-diagram > div i { color: var(--muted); font: .65rem/1 ui-monospace, monospace; }
.nominal-diagram > b { display: block; margin: -1rem 0 1rem; color: var(--cobalt); font: 700 .65rem/1 ui-monospace, monospace; }

.checker-band, .limit-note {
  display: grid;
  grid-template-columns: minmax(150px, .23fr) 1fr;
  gap: 2rem;
  align-items: start;
  margin-top: 4rem;
  padding: 1.5rem;
  color: white;
  background: var(--cobalt-deep);
}
.checker-band span { color: var(--sulfur); }
.checker-band p { margin: 0; }
.limit-note { display: block; color: var(--ink); border: 1px solid #bc9f14; background: rgba(232,242,58,.18); }

.module-flow {
  display: grid;
  grid-template-columns: 1fr auto 1fr auto 1fr auto 1fr;
  gap: 1rem;
  align-items: center;
  margin: 4rem 0 6rem;
}
.module-flow > div { min-height: 110px; display: flex; flex-direction: column; justify-content: center; padding: 1rem; border: 1px solid var(--ink); background: white; }
.module-flow code { padding: 0; background: none; font-size: .73rem; }
.module-flow span { margin-top: .5rem; color: var(--muted); font-size: .72rem; }
.module-flow > b, .module-flow > i { color: var(--cobalt); font-style: normal; text-align: center; }
.module-flow .exports-node { color: var(--ink); border-color: var(--cobalt); background: var(--sulfur); }

.evolve-plate {
  display: grid;
  grid-template-columns: 1fr minmax(150px, .35fr) 1fr;
  gap: 1.5rem;
  align-items: center;
  margin: 4rem 0 6rem;
  padding: clamp(1.5rem, 3vw, 3rem);
  border: 1px solid var(--ink);
  background: white;
}
.evolve-plate > div:not(.evolve-arrow) { min-height: 190px; padding: 1.2rem; border: 1px solid var(--cobalt); background: rgba(25,86,209,.04); }
.evolve-plate span { display: block; margin-bottom: 2rem; color: var(--muted); font: 700 .64rem/1 ui-monospace, monospace; }
.evolve-plate code { padding: 0; background: none; line-height: 1.8; }
.evolve-arrow { text-align: center; }
.evolve-arrow b, .evolve-arrow span, .evolve-arrow i { display: block; }
.evolve-arrow b { color: var(--cobalt); font: 800 1.1rem/1 ui-monospace, monospace; }
.evolve-arrow span { margin: .5rem 0; font-size: .68rem; }
.evolve-arrow i { color: var(--cobalt); font-size: 3rem; font-style: normal; }
.evolve-plate > p { grid-column: 1 / -1; margin: 0; padding-top: 1rem; border-top: 1px solid var(--grid); color: var(--muted); font: .7rem/1.5 ui-monospace, monospace; text-align: center; }
.persistence-ledger { grid-template-columns: repeat(4, 1fr); margin: 5rem 0 3rem; }
.persistence-ledger span { color: var(--cobalt); font: 750 .68rem/1 ui-monospace, monospace; letter-spacing: .06em; }
.persistence-ledger p { margin: 1rem 0 0; color: var(--muted); font-size: .82rem; }

.collection-demo { position: relative; max-width: 840px; margin: 4rem auto 6rem; padding: 2rem; border: 1px solid var(--ink); background: white; }
.collection-row { display: grid; grid-template-columns: 50px 1fr auto; gap: 1rem; align-items: center; padding: .9rem; border-bottom: 1px solid var(--grid); }
.collection-row b { color: var(--cobalt); font: 700 .7rem/1 ui-monospace, monospace; }
.collection-row code { padding: 0; background: none; }
.collection-row span { color: var(--ink); background: var(--sulfur); padding: .3rem .45rem; font: 700 .62rem/1 ui-monospace, monospace; }
.collection-row.active { background: rgba(25,86,209,.04); }
.collection-demo svg { display: block; width: 100%; height: 75px; }
.collection-demo svg path { fill: none; stroke: var(--cobalt); stroke-width: 2; }
.collection-demo svg circle { fill: var(--sulfur); stroke: var(--ink); }
.collection-demo > p { margin: .5rem 0 0; color: var(--muted); font-size: .85rem; text-align: center; }
.api-list { margin: 1rem 0; }
.api-list > div { display: grid; grid-template-columns: 1fr 1.2fr; gap: 1rem; padding: .65rem 0; border-top: 1px solid var(--grid); }
.api-list dt, .api-list dd { margin: 0; }
.api-list dd { color: var(--muted); font-size: .85rem; }

.signals-chapter { background: linear-gradient(to bottom, rgba(25,86,209,.05), rgba(244,247,248,.88) 36%); }
.signal-flow { display: grid; grid-template-columns: repeat(7, auto); align-items: center; gap: .8rem; margin: 4rem 0 6rem; overflow-x: auto; }
.signal-flow > div { min-width: 150px; padding: 1.1rem; border: 1px solid var(--cobalt); background: white; }
.signal-flow > div.effect { color: var(--ink); border-color: var(--ink); background: var(--sulfur); }
.signal-flow span { display: block; margin-bottom: .8rem; color: var(--muted); font: 700 .62rem/1 ui-monospace, monospace; }
.signal-flow code { padding: 0; background: none; font-size: .72rem; }
.signal-flow > i { color: var(--cobalt); font: 700 .62rem/1 ui-monospace, monospace; font-style: normal; }
.signal-rules > div { display: grid; grid-template-columns: 44px 1fr; gap: 1rem; padding: .9rem 0; border-top: 1px solid var(--grid); }
.signal-rules > div:last-child { border-bottom: 1px solid var(--grid); }
.signal-rules b { color: var(--cobalt); font: 700 .7rem/1 ui-monospace, monospace; }
.signal-rules p { margin: 0; color: #33454e; font-size: .88rem; }
.keyed-diagram { align-self: center; }
.key-source { padding: 1rem; border: 1px solid var(--ink); background: var(--sulfur); }
.key-source span { margin-right: 1rem; font: 700 .65rem/1 ui-monospace, monospace; }
.key-source code { padding: 0; background: none; }
.key-branches { display: grid; grid-template-columns: repeat(3, 1fr); gap: .7rem; margin-top: 1.2rem; }
.key-branches > div { padding: 1rem; border: 1px solid var(--cobalt); background: white; }
.key-branches b, .key-branches span { display: block; }
.key-branches b { margin-bottom: .8rem; color: var(--cobalt); }
.key-branches span { color: var(--muted); font-size: .72rem; }
.key-branches .dead { opacity: .55; border-style: dashed; text-decoration: line-through; }

.migration-sequence { display: grid; grid-template-columns: 1fr auto 1.5fr auto 1.5fr auto 1fr; gap: .75rem; align-items: center; margin: 4rem 0 6rem; overflow-x: auto; }
.migration-sequence > div { min-width: 145px; min-height: 150px; padding: 1rem; border: 1px solid var(--ink); background: white; }
.migration-sequence div.active { background: var(--sulfur); }
.migration-sequence b, .migration-sequence span, .migration-sequence small { display: block; }
.migration-sequence b { color: var(--cobalt); font: 800 1.6rem/1 "Arial Narrow", sans-serif; }
.migration-sequence span { margin: 1rem 0; font: .74rem/1.45 ui-monospace, monospace; }
.migration-sequence small { color: var(--muted); }
.migration-sequence > i { color: var(--cobalt); font: 700 .62rem/1 ui-monospace, monospace; font-style: normal; }
.wide-code { margin: 3rem 0 5rem; }
.wide-code pre { min-height: 360px; }

.relations-board { display: grid; grid-template-columns: repeat(3, 1fr); border-left: 1px solid var(--ink); border-top: 1px solid var(--ink); margin: 4rem 0 6rem; }
.relations-board > div { min-height: 310px; padding: 1.4rem; border-right: 1px solid var(--ink); border-bottom: 1px solid var(--ink); background: white; }
.relations-board span { color: var(--cobalt); font: 750 .65rem/1 ui-monospace, monospace; letter-spacing: .08em; }
.relations-board b { display: block; margin: 1.5rem 0 1rem; font: 800 clamp(1.5rem, 2.5vw, 2.1rem)/1 "Arial Narrow", sans-serif; }
.relations-board p { color: var(--muted); font-size: .87rem; }
.relations-board code { display: block; margin-top: 2rem; padding: 1rem; color: var(--terminal-copy); background: var(--terminal); font-size: .7rem; line-height: 1.7; }
.peer-topology { position: relative; display: grid; grid-template-columns: 210px 1fr 210px; align-items: center; max-width: 960px; min-height: 270px; margin: 5rem auto; }
.peer { position: relative; z-index: 2; padding: 1.4rem; border: 1px solid var(--ink); background: white; }
.peer.remote { background: var(--terminal); color: white; }
.peer span, .peer b, .peer small { display: block; }
.peer span { color: var(--cobalt); font: 700 .63rem/1 ui-monospace, monospace; }
.peer b { margin: .7rem 0; font: 800 1.5rem/1 "Arial Narrow", sans-serif; }
.peer small { color: var(--muted); }
.peer.remote small { color: #aec1c7; }
.peer-topology svg { width: 100%; }
.peer-topology svg path { fill: none; stroke: var(--cobalt); stroke-width: 3; }
.peer-topology svg path.dash { stroke-dasharray: 7 6; }
.peer-topology svg marker path { fill: var(--cobalt); }
.topology-label { position: absolute; left: 50%; transform: translateX(-50%); padding: .3rem .5rem; background: var(--paper); font: 700 .62rem/1 ui-monospace, monospace; }
.topology-label.push { top: 34px; }
.topology-label.pull { bottom: 31px; }
.server-strip { display: grid; grid-template-columns: 1.2fr auto repeat(3, 1fr); gap: 0; align-items: stretch; margin: 5rem 0; border: 1px solid var(--ink); }
.server-strip > div { padding: 1rem; border-right: 1px solid var(--grid); background: white; }
.server-strip > p { display: grid; place-items: center; margin: 0; padding: .5rem; color: var(--muted); font-size: .72rem; }
.server-strip code { display: block; padding: 0; margin-bottom: .5rem; background: none; font-size: .75rem; }

.browser-chapter { background-color: rgba(25,86,209,.04); }
.browser-loop { display: grid; grid-template-columns: 1fr auto 1fr auto 1fr auto 1fr; gap: .75rem; align-items: center; margin: 4rem 0 6rem; overflow-x: auto; }
.browser-loop > div { min-width: 155px; padding: 1rem; border: 1px solid var(--ink); background: white; }
.browser-loop div.loop-back { background: var(--sulfur); }
.browser-loop span, .browser-loop b { display: block; }
.browser-loop span { color: var(--cobalt); font: 700 .62rem/1 ui-monospace, monospace; }
.browser-loop b { margin-top: .7rem; font-size: .8rem; }
.browser-loop > i { color: var(--cobalt); font: 700 .6rem/1 ui-monospace, monospace; font-style: normal; }
.browser-code-pair .code-instrument pre { min-height: 410px; }
.dom-api { grid-template-columns: repeat(5, 1fr); margin: 5rem 0; }
.dom-api code { display: block; padding: 0; margin-bottom: 1rem; background: none; font-size: .68rem; }
.dom-api span { color: var(--muted); font-size: .75rem; }
.run-web { margin-top: 5rem; border: 1px solid var(--ink); background: var(--terminal); color: white; }
.run-web > div { display: flex; justify-content: space-between; align-items: center; padding: .7rem 1rem; border-bottom: 1px solid var(--terminal-line); }
.run-web > div span { color: var(--sulfur); }
.run-web > code { display: block; overflow-x: auto; padding: 2rem; color: var(--terminal-copy); background: none; white-space: nowrap; }
.run-web p { margin: 0; padding: 1rem 2rem; color: #c1d1d5; border-top: 1px solid var(--terminal-line); font-size: .85rem; }
.run-web a { color: var(--sulfur); }

.reference-index { display: flex; flex-wrap: wrap; gap: 0; margin: 3rem 0 4rem; border-top: 1px solid var(--ink); border-left: 1px solid var(--ink); }
.reference-index a { min-width: 120px; flex: 1; padding: .75rem; border-right: 1px solid var(--ink); border-bottom: 1px solid var(--ink); color: var(--ink); background: white; font: 700 .68rem/1 ui-monospace, monospace; text-align: center; text-decoration: none; }
.reference-index a:hover { color: white; background: var(--cobalt); }
.reference-group { margin: 0; border-top: 1px solid var(--ink); }
.reference-group:last-of-type { border-bottom: 1px solid var(--ink); }
.reference-group summary { display: flex; justify-content: space-between; align-items: center; padding: 1rem .25rem; cursor: pointer; list-style: none; }
.reference-group summary::-webkit-details-marker { display: none; }
.reference-group summary span { font: 800 1rem/1 ui-monospace, monospace; }
.reference-group summary b { min-width: 42px; padding: .35rem; color: var(--cobalt); border: 1px solid var(--grid); font: 700 .65rem/1 ui-monospace, monospace; text-align: center; }
.reference-group summary:hover span { color: var(--cobalt); }
.reference-group[open] summary b { color: var(--ink); background: var(--sulfur); border-color: var(--ink); }
.reference-group .reference-table { margin: 0 0 2.5rem; }
.reference-note { margin: 1rem 0 2rem; color: var(--muted); }
.example-map { display: grid; grid-template-columns: repeat(2, 1fr); margin: 6rem 0; border-top: 1px solid var(--ink); border-left: 1px solid var(--ink); }
.example-map > div { display: grid; grid-template-columns: 46px 1fr; gap: .4rem 1rem; padding: 1rem; border-right: 1px solid var(--ink); border-bottom: 1px solid var(--ink); background: white; }
.example-map b { grid-row: 1 / span 2; color: var(--cobalt); font: 700 .75rem/1 ui-monospace, monospace; }
.example-map span { font-weight: 700; }
.example-map code { padding: 0; color: var(--muted); background: none; font-size: .68rem; }
.finish-block { margin: 6rem 0 0; padding: clamp(2rem, 6vw, 6rem); color: white; background: var(--terminal); }
.finish-block > span { color: var(--sulfur); }
.finish-block h2 { margin-top: 1rem; }
.finish-block p { max-width: var(--measure); color: #c1d1d5; }
.finish-block .primary-action { margin-top: 2rem; }

.copy-status {
  position: fixed;
  z-index: 80;
  right: 1.25rem;
  bottom: 1.25rem;
  padding: .75rem 1rem;
  color: var(--ink);
  border: 1px solid var(--ink);
  background: var(--sulfur);
  box-shadow: 6px 8px 20px rgba(21,35,43,.2);
  font: 750 .7rem/1 ui-monospace, monospace;
  opacity: 0;
  transform: translateY(12px);
  pointer-events: none;
  transition: opacity .16s ease, transform .25s var(--ease-out);
}
.copy-status.show { opacity: 1; transform: translateY(0); }

@media (max-width: 1120px) {
  :root { --rail: 226px; }
  .hero-heading { grid-template-columns: .8fr 1fr; }
  .hero-note { display: none; }
  .hero-thesis { grid-template-columns: 1fr; }
  .state-instrument { min-height: 360px; }
  .hero-code pre { min-height: 280px; }
  .types-strip { grid-template-columns: repeat(3, 1fr); }
  .types-strip > div:last-child { grid-column: span 2; }
  .persistence-ledger { grid-template-columns: repeat(2, 1fr); }
  .dom-api { grid-template-columns: repeat(2, 1fr); }
  .relations-board { grid-template-columns: 1fr; }
  .relations-board > div { min-height: 0; }
  .server-strip { grid-template-columns: 1fr 1fr; }
  .server-strip > p { display: none; }
  .server-strip > div:nth-last-child(-n+3) { border-top: 1px solid var(--grid); }
}

@media (max-width: 820px) {
  html { scroll-padding-top: 4rem; }
  body { background-size: 20px 20px; }
  .mobile-bar {
    position: fixed;
    z-index: 45;
    inset: 0 0 auto;
    display: flex;
    height: 54px;
    justify-content: space-between;
    align-items: center;
    padding: 0 1rem;
    color: white;
    background: var(--terminal);
    box-shadow: 0 8px 22px rgba(16,40,48,.2);
  }
  .mobile-brand { color: white; font: 800 .9rem/1 ui-monospace, monospace; text-decoration: none; }
  .mobile-brand span { color: #9db3ba; font-size: .62rem; }
  .menu-button { min-height: 44px; display: flex; gap: .7rem; align-items: center; border: 0; color: white; background: transparent; font: 700 .65rem/1 ui-monospace, monospace; cursor: pointer; }
  .menu-button i, .menu-button i::before, .menu-button i::after { display: block; width: 18px; height: 1px; background: white; content: ""; }
  .menu-button i { position: relative; }
  .menu-button i::before { position: absolute; top: -5px; }
  .menu-button i::after { position: absolute; top: 5px; }
  .menu-button[aria-expanded="true"] i { background: transparent; }
  .menu-button[aria-expanded="true"] i::before { top: 0; transform: rotate(45deg); }
  .menu-button[aria-expanded="true"] i::after { top: 0; transform: rotate(-45deg); }

  .course-rail { width: min(88vw, 340px); top: 54px; transform: translateX(-105%); box-shadow: 12px 0 30px rgba(16,40,48,.22); transition: transform .3s var(--ease-out); }
  body.nav-open .course-rail { transform: translateX(0); }
  .rail-brand { display: none; }
  main { margin-left: 0; padding-top: 54px; }
  .hero { min-height: auto; }
  .hero::before { top: .4rem; }
  .hero-heading { grid-template-columns: 1fr; gap: 1rem; padding: 4.7rem 1.25rem 2rem; }
  .hero-heading h1 { font-size: clamp(4rem, 22vw, 6rem); }
  .hero-heading > p { font-size: 1.25rem; }
  .hero-thesis { padding: 1.25rem; }
  .hero-actions { padding: 1rem 1.25rem; }
  .hero-actions > p { display: none; }
  .chapter { grid-template-columns: 54px minmax(0, 1fr); }
  .chapter-marker { padding: 4rem .6rem; }
  .chapter-marker b { top: 4.5rem; font-size: 1.6rem; }
  .chapter-marker span { top: 7rem; font-size: .55rem; }
  .chapter-body { padding: 4rem clamp(1.25rem, 5vw, 2.5rem); }
  .chapter-header { margin-bottom: 3.5rem; }
  h2 { font-size: clamp(2.5rem, 11vw, 4.5rem); }
  .lab-pair, .lesson-columns, .feature-plate, .nominal-lab, .each-lab, .reading-grid { grid-template-columns: 1fr; }
  .lesson-columns.reverse > :first-child, .lesson-columns.reverse > :last-child { order: initial; }
  .setup-strip, .syntax-board { grid-template-columns: 1fr; }
  .types-strip { grid-template-columns: repeat(2, 1fr); }
  .types-strip > div:last-child { grid-column: auto; }
  .type-equation { grid-template-columns: 1fr; }
  .type-equation > i { transform: rotate(90deg); text-align: center; }
  .module-flow { grid-template-columns: 1fr; }
  .module-flow > b, .module-flow > i { transform: rotate(90deg); }
  .evolve-plate { grid-template-columns: 1fr; }
  .evolve-arrow i { transform: rotate(90deg); }
  .checkpoint { grid-template-columns: 1fr; }
  .checkpoint::before { left: 1.5rem; }
  .checkpoint details { grid-column: 1; }
  .peer-topology { grid-template-columns: 1fr; gap: 1rem; }
  .peer-topology svg, .topology-label { display: none; }
  .dom-api { grid-template-columns: 1fr; }
  .example-map { grid-template-columns: 1fr; }
  .code-instrument pre { font-size: .75rem; }
}

@media (max-width: 520px) {
  .hero-heading { padding-left: 1rem; padding-right: 1rem; }
  .hero-thesis { padding: 1rem; }
  .state-instrument { min-height: 480px; }
  .instrument-thesis { position: static; max-width: none; margin-top: 2rem; }
  .state-stack { top: 12rem; width: calc(100% - 2.5rem); }
  .trace-svg { height: 35%; }
  .hero-actions { display: block; }
  .primary-action { width: 100%; }
  .chapter { grid-template-columns: 38px minmax(0, 1fr); }
  .chapter-marker { padding-left: .35rem; padding-right: .35rem; }
  .chapter-marker b { font-size: 1.25rem; }
  .chapter-marker span { display: none; }
  .chapter-body { padding-left: 1rem; padding-right: 1rem; }
  .code-output { grid-template-columns: 86px 1fr; font-size: .68rem; }
  .syntax-board, .types-strip, .persistence-ledger { grid-template-columns: 1fr; }
  .types-strip > div:last-child { grid-column: auto; }
  .nominal-diagram > div { grid-template-columns: 1fr; }
  .nominal-diagram > div i { text-align: center; }
  .checker-band { grid-template-columns: 1fr; }
  .collection-row { grid-template-columns: 35px 1fr; }
  .collection-row span { grid-column: 2; justify-self: start; }
  .key-branches { grid-template-columns: 1fr; }
  .server-strip { grid-template-columns: 1fr; }
  .server-strip > div { border-top: 1px solid var(--grid); }
  .run-web > code { padding: 1.25rem; }
  th, td { padding: .7rem; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { scroll-behavior: auto !important; animation-duration: .001ms !important; animation-iteration-count: 1 !important; transition-duration: .001ms !important; }
  .trace-path { stroke-dashoffset: 0; }
}

@media print {
  body { background: white; font-size: 11pt; }
  .course-rail, .mobile-bar, .copy-button, .hero-actions, .copy-status { display: none !important; }
  main { margin: 0; padding: 0; }
  .hero, .chapter { break-inside: avoid; }
  .chapter { grid-template-columns: 70px 1fr; }
  .chapter-body { padding: 2rem; }
  .code-instrument { box-shadow: none; print-color-adjust: exact; }
}