:root {
  --ink: #111111;
  --muted: #666666;
  --faint: #d8d8d8;
  --paper: #ffffff;
  --accent: #d71920;
  --body: Georgia, "Iowan Old Style", "Times New Roman", serif;
  --sans: "Helvetica Neue", Arial, sans-serif;
  --mono: "IBM Plex Mono", "SFMono-Regular", Consolas, monospace;
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --measure: 34rem;
  --page-inline: clamp(1.25rem, 5vw, 5rem);
  --cover-title-size: clamp(3.2rem, 9vw, 5.8rem);
  --chapter-title-size: 2.05rem;
  --body-size: 1rem;
  --statement-size: 1.35rem;
}

* {
  box-sizing: border-box;
}

html {
  color: var(--ink);
  background: var(--paper);
  font-family: var(--body);
  font-size: 16px;
}

body {
  margin: 0;
}

.paper {
  counter-reset: section;
}

.cover {
  min-height: var(--page-height, 100vh);
  display: grid;
  grid-template-rows: auto 1fr auto;
  padding: var(--cover-padding, var(--space-12) 0);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: var(--space-3);
  font-family: var(--sans);
  font-size: 0.82rem;
  font-weight: 700;
  letter-spacing: 0;
  text-transform: uppercase;
}

.cover__title {
  align-self: center;
  max-width: var(--cover-measure, 35rem);
}

h1,
h2 {
  font-family: var(--sans);
  line-height: 1.02;
  letter-spacing: 0;
  break-after: avoid;
}

.cover h1 {
  margin: 0;
  font-size: var(--cover-title-size);
  font-weight: 760;
}

.subtitle {
  max-width: 26rem;
  margin: var(--space-6) 0 0;
  color: var(--muted);
  font-family: var(--sans);
  font-size: 1.05rem;
  line-height: 1.45;
}

.cover__meta {
  display: grid;
  gap: var(--space-1);
  color: var(--muted);
  font-family: var(--sans);
  font-size: 0.85rem;
}

.publication-landing {
  min-height: var(--page-height, 100vh);
  display: grid;
  grid-template-rows: auto 1fr auto;
  gap: var(--space-12);
  padding: var(--cover-padding, var(--space-12) 0);
}

.publication-landing__title {
  align-self: center;
  max-width: var(--cover-measure, 35rem);
}

.publication-landing h1 {
  margin: 0;
  font-size: var(--cover-title-size);
  font-weight: 760;
}

.publication-landing__title > p:not(.series-title, .subtitle) {
  max-width: 30rem;
  color: var(--ink);
}

.reading-options {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: var(--space-4);
}

.reading-option {
  display: grid;
  gap: var(--space-2);
  min-height: 9rem;
  align-content: start;
  padding: var(--space-5) 0 0;
  border-top: 2px solid var(--ink);
  color: inherit;
  text-decoration: none;
}

.reading-option:hover span,
.reading-option:focus span {
  text-decoration: underline;
  text-underline-offset: 0.12em;
}

.reading-option span,
.version-nav__label {
  font-family: var(--sans);
  font-size: 0.85rem;
  font-weight: 700;
  line-height: 1.25;
  text-transform: uppercase;
}

.reading-option small,
.version-nav__detail {
  color: var(--muted);
  font-family: var(--body);
  font-size: 0.9rem;
  line-height: 1.45;
}

.version-nav {
  display: flex;
  align-items: start;
  justify-content: space-between;
  gap: var(--space-6);
  max-width: var(--measure);
  margin: 0 auto var(--space-12);
  padding: var(--space-5) 0;
  border-top: 1px solid var(--faint);
  border-bottom: 1px solid var(--faint);
  font-family: var(--sans);
}

.version-nav div {
  display: grid;
  gap: var(--space-1);
}

.version-nav a {
  flex: 0 0 auto;
  font-size: 0.85rem;
  font-weight: 700;
  line-height: 1.35;
  text-underline-offset: 0.16em;
}

.chapter,
.practice {
  max-width: var(--measure);
  margin: 0 auto;
  padding: var(--section-padding, var(--space-16) 0 var(--space-12));
}

.chapter--opening {
  break-before: page;
}

.section-kicker {
  display: block;
  margin-bottom: var(--space-4);
  color: var(--accent);
  font-family: var(--sans);
  font-size: 0.8rem;
  font-weight: 700;
}

.chapter h1,
.practice h1 {
  margin: 0 0 var(--space-8);
  font-size: var(--chapter-title-size);
  font-weight: 720;
}

.chapter h2,
.practice h2 {
  margin: var(--space-10) 0 var(--space-4);
  font-size: 1.15rem;
  font-weight: 720;
}

p {
  margin: 0 0 var(--space-4);
  font-size: var(--body-size);
  line-height: 1.55;
  orphans: 3;
  widows: 3;
}

.question,
.voice {
  margin: var(--space-6) 0;
  padding: 0 0 0 var(--space-4);
  border-left: 2px solid var(--faint);
}

.question p,
.voice p {
  color: #222222;
  font-style: italic;
}

.question {
  max-width: 30rem;
}

.voice {
  max-width: 24rem;
  font-family: var(--sans);
}

strong {
  font-weight: 700;
}

hr {
  display: none;
}

.statement {
  max-width: 27rem;
  margin: var(--space-12) auto;
  padding: var(--space-8) 0;
  break-inside: avoid;
}

.statement p {
  margin: 0;
  font-family: var(--sans);
  font-size: var(--statement-size);
  font-weight: 650;
  line-height: 1.28;
}

.statement span {
  display: block;
}

.practice {
  border-top: 1px solid var(--faint);
}

.practice h2 {
  margin-top: var(--space-8);
  padding-top: var(--space-2);
  font-size: 1rem;
  text-transform: uppercase;
}

.practice-item {
  margin-top: var(--space-8);
}

.practice-structure {
  display: grid;
  gap: var(--space-5);
  margin: var(--space-6) 0 0;
}

.practice-structure div {
  display: grid;
  grid-template-columns: 7rem 1fr;
  column-gap: var(--space-4);
  break-inside: avoid;
}

.practice-structure dt {
  color: var(--muted);
  font-family: var(--sans);
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.practice-structure dd {
  margin: 0;
  font-size: var(--body-size);
  line-height: 1.5;
}

a {
  color: inherit;
}

.citation {
  font-family: var(--sans);
  font-size: 0.72em;
  line-height: 0;
  vertical-align: super;
}

.citation a {
  color: var(--accent);
  text-decoration: none;
}

.citation a:hover,
.citation a:focus {
  text-decoration: underline;
  text-underline-offset: 0.14em;
}

.sources {
  border-top: 1px solid var(--faint);
}

.sources h1 {
  margin-bottom: var(--space-6);
  font-size: 1.2rem;
}

.sources-list {
  margin: 0;
  padding-left: 1.35rem;
  color: var(--muted);
}

.sources-list li {
  margin-bottom: var(--space-4);
  padding-left: var(--space-2);
  font-size: 0.86rem;
  line-height: 1.45;
}

.sources-list li:target {
  color: var(--ink);
}

.sources-list a {
  color: var(--ink);
  text-decoration-thickness: 1px;
  text-underline-offset: 0.16em;
}

@media (max-width: 640px) {
  .reading-options {
    grid-template-columns: 1fr;
  }

  .reading-option {
    min-height: 0;
  }

  .version-nav {
    display: grid;
  }
}

.series-title {
  margin: 0 0 var(--space-3);
  color: var(--muted);
  font-family: var(--sans);
  font-size: 1.08rem;
  font-weight: 700;
  line-height: 1.15;
}

.narrative-cover h1 {
  max-width: 24rem;
}

.narrative-chapter {
  position: relative;
}

.narrative-sequence {
  display: grid;
  gap: var(--space-2);
  margin: var(--space-10) 0 0;
  padding: var(--space-6) 0 0;
  border-top: 1px solid var(--faint);
  color: var(--muted);
  font-family: var(--sans);
  font-size: 0.78rem;
  line-height: 1.3;
  list-style: none;
}

.narrative-sequence li {
  max-width: 12rem;
}

.narrative-sequence [aria-current="step"] {
  color: var(--ink);
  font-weight: 700;
}

.technical-briefing,
.engineering-note {
  margin: var(--space-8) 0;
  padding: var(--space-5) 0 0;
  border-top: 1px solid var(--ink);
  break-inside: avoid;
}

.technical-briefing h2,
.engineering-note h2 {
  margin: 0 0 var(--space-5);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.technical-briefing dl {
  display: grid;
  gap: var(--space-4);
  margin: 0;
}

.technical-briefing div {
  display: grid;
  grid-template-columns: 9rem 1fr;
  column-gap: var(--space-4);
}

.technical-briefing dt {
  color: var(--muted);
  font-family: var(--sans);
  font-size: 0.72rem;
  font-weight: 700;
  line-height: 1.35;
}

.technical-briefing dd {
  margin: 0;
  font-size: 0.92rem;
  line-height: 1.45;
}

.engineering-note p {
  margin: 0;
  color: var(--muted);
  font-size: 0.94rem;
  line-height: 1.45;
}