:root {
  --ink: #12110e;
  --ink-deep: #0b0a08;
  --paper: #f4efe4;
  --paper-2: #ebe3d2;
  --rule: #d4c7ae;
  --muted: #6b6358;
  --jev: #c63b22;
  --gpt: #2a5d6e;
  --human: #2f5d3a;
  --gold: #b8860b;
  /* --gold is 2.6 to 3.0:1 on the paper backgrounds; this one clears 5:1 there. */
  --gold-ink: #7a5a06;
  --jev-soft: #e07a68;
  --gpt-soft: #7a8b90;
  --neutral: #8a9698;
  --rail: 11.5rem;
  --serif: "Fraunces", "Iowan Old Style", "Times New Roman", serif;
  --sans: "Sora", "Helvetica Neue", sans-serif;
  --mono: "IBM Plex Mono", ui-monospace, monospace;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
:focus-visible { outline: 2px solid var(--gold); outline-offset: 2px; }
body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 1.05rem;
  line-height: 1.55;
}
img, svg { max-width: 100%; }
a { color: inherit; }
code {
  font-family: var(--mono);
  /* Mono runs optically small next to Sora; 0.92 lines the cap heights up. */
  font-size: 0.92em;
}
.skip {
  position: absolute;
  left: -999px;
}
.skip:focus {
  left: 1rem;
  top: 1rem;
  background: var(--paper);
  padding: 0.4rem 0.7rem;
  z-index: 9;
}

.rail {
  position: fixed;
  inset: 0 auto 0 0;
  width: var(--rail);
  padding: 1.4rem 1.1rem;
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
  border-right: 1px solid color-mix(in srgb, var(--paper) 12%, transparent);
  background: var(--ink-deep);
  color: var(--paper);
  z-index: 4;
}
.rail-mark {
  font-family: var(--serif);
  font-style: italic;
  font-size: 1.4rem;
  text-decoration: none;
}
.rail ol {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 0.55rem;
}
.rail a {
  text-decoration: none;
  color: color-mix(in srgb, var(--paper) 62%, transparent);
  font-size: 0.78rem;
  letter-spacing: 0.01em;
}
.rail a span {
  display: block;
  font-family: var(--mono);
  font-size: 0.66rem;
  color: var(--gold);
  margin-bottom: 0.1rem;
}
.rail a.is-on { color: var(--paper); }
.rail-repo {
  margin-top: auto;
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

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

.hero {
  min-height: 100vh;
  background:
    radial-gradient(1200px 500px at 80% -10%, color-mix(in srgb, var(--jev) 22%, transparent), transparent 60%),
    var(--ink-deep);
  color: var(--paper);
  padding: 4.5rem 7vw 5rem;
  display: flex;
  align-items: flex-end;
}
.hero-inner { max-width: 58rem; }
.kicker, .bench-kicker {
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--gold);
  margin: 0 0 1rem;
}
.paper .kicker, .paper .bench-kicker, .bench .bench-kicker { color: var(--gold-ink); }
.hero h1 {
  font-family: var(--serif);
  font-weight: 400;
  font-size: clamp(3rem, 8vw, 6.4rem);
  line-height: 0.92;
  letter-spacing: -0.035em;
  margin: 0 0 1.4rem;
}
.hero h1 em {
  display: block;
  font-style: italic;
  color: color-mix(in srgb, var(--paper) 82%, var(--jev));
}
.lede {
  max-width: 40rem;
  font-size: 1.12rem;
  color: color-mix(in srgb, var(--paper) 78%, transparent);
}
.hero-board {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 1.6rem 2.2rem;
  align-items: center;
  margin: 2.4rem 0 1.4rem;
}
.stamp {
  width: 9.4rem;
  height: 9.4rem;
  border: 3px solid var(--jev);
  border-radius: 50%;
  display: grid;
  place-content: center;
  text-align: center;
  transform: rotate(-11deg);
  color: var(--jev);
  box-shadow: inset 0 0 0 1px color-mix(in srgb, var(--jev) 45%, transparent);
}
.stamp span {
  font-family: var(--mono);
  font-size: 0.64rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
}
.stamp strong {
  font-family: var(--serif);
  font-size: 1.7rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}
.hero-stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(6rem, 1fr));
  gap: 1rem 1.2rem;
  margin: 0;
}
.hero-stats div { margin: 0; }
.hero-stats dt {
  font-family: var(--mono);
  font-size: 0.64rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: color-mix(in srgb, var(--paper) 50%, transparent);
}
.hero-stats dd {
  margin: 0.15rem 0 0;
  font-family: var(--serif);
  font-size: 1.55rem;
}
/* The compared subset is the headline; the sample it came from is context, not a second stat. */
.stat-note {
  font-size: 0.62em;
  color: color-mix(in srgb, var(--paper) 45%, transparent);
  white-space: nowrap;
}
.hero-note {
  max-width: 38rem;
  color: color-mix(in srgb, var(--paper) 55%, transparent);
  font-size: 0.92rem;
}
ul.hero-note {
  padding-left: 1.05rem;
  margin: 0;
}
ul.hero-note li { margin-bottom: 0.5rem; }

.chapter {
  padding: 5.5rem 7vw 4.5rem;
  /* Containing block for the ghost numeral, so it anchors to the full content
     width rather than to the 40rem text column it used to sit on top of. */
  position: relative;
}
.chapter-head {
  max-width: 40rem;
  margin-bottom: 2.4rem;
}
.chapter-no {
  position: absolute;
  /* 7vw matches the chapter's own gutter, so the numeral lines up with the
     content edge instead of bleeding off the viewport. */
  right: 7vw;
  top: 2.9rem;
  font-family: var(--serif);
  font-size: clamp(4.5rem, 10vw, 7.5rem);
  letter-spacing: -0.06em;
  color: inherit;
  opacity: 0.1;
  line-height: 1;
  pointer-events: none;
}
.chapter-head h2 {
  font-family: var(--serif);
  font-weight: 400;
  font-size: clamp(2.1rem, 4vw, 3.4rem);
  line-height: 1.05;
  letter-spacing: -0.03em;
  margin: 0 0 1rem;
}
.paper { background: var(--paper); }
.ink {
  background: var(--ink);
  color: var(--paper);
}
.ink .muted, .ink .source, .ink figcaption, .ink .frame > p { color: color-mix(in srgb, var(--paper) 58%, transparent); }
.ink .frame { background: color-mix(in srgb, var(--paper) 5%, transparent); border-color: color-mix(in srgb, var(--paper) 14%, transparent); }
.ink .chart { color: var(--paper); }

.bench {
  background: var(--paper-2);
  border: 1px solid var(--rule);
  padding: 1.2rem 1.3rem 1rem;
}
.bench-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-bottom: 1.2rem;
}
.bench-tabs button, .bench-nav button, .btn {
  font-family: var(--sans);
  background: transparent;
  color: inherit;
  border: 1px solid var(--rule);
  padding: 0.45rem 0.75rem;
  cursor: pointer;
}
.bench-tabs button[aria-selected="true"] {
  background: var(--ink);
  color: var(--paper);
  border-color: var(--ink);
}
.bench-panel { display: none; }
.bench-panel.is-on { display: block; }
.bench-panel h3 {
  font-family: var(--serif);
  font-weight: 400;
  font-size: 1.8rem;
  margin: 0 0 0.7rem;
}
.persona {
  list-style: none;
  padding: 0;
  margin: 1.2rem 0 0;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.45rem 1.4rem;
}
.persona li {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  border-bottom: 1px solid var(--rule);
  padding: 0.28rem 0;
  font-size: 0.92rem;
}
.persona span {
  font-family: var(--mono);
  font-size: 0.68rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
}
.stem {
  margin: 0;
  padding: 1rem 0 0;
  font-family: var(--serif);
  font-size: 1.25rem;
  line-height: 1.4;
}
.options {
  padding-left: 1.1rem;
  color: var(--muted);
}
.split {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.4rem;
}
.arm-label {
  font-family: var(--mono);
  font-size: 0.75rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin: 0 0 0.2rem;
}
.arm-label.jev { color: var(--jev); }
.arm-label.gpt { color: var(--gpt); }
.muted { color: var(--muted); }
.bench-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: 1.2rem;
  padding-top: 0.8rem;
  border-top: 1px solid var(--rule);
}
.bench-nav p { margin: 0; font-family: var(--mono); font-size: 0.78rem; }

.frame {
  border: 1px solid var(--rule);
  background: color-mix(in srgb, var(--paper) 70%, white);
  padding: 1.1rem 1.2rem 1.3rem;
  margin: 0 0 1.4rem;
}
.ink .frame { background: #171614; }
figcaption, .frame > p {
  font-size: 0.92rem;
  color: var(--muted);
  margin: 0 0 1rem;
  max-width: 46rem;
}
.chart { min-height: 8rem; }
.chart .bench-kicker { margin: 1.1rem 0 0.35rem; }
.chart svg { display: block; width: 100%; height: auto; }
.chart .bar {
  transform-box: fill-box;
  transform-origin: left center;
  transform: scaleX(0.04);
  animation: bar-in 0.9s cubic-bezier(0.2, 0.7, 0.2, 1) forwards;
}
.chart .label { font-family: var(--sans); font-size: 12px; }
.chart .value { font-family: var(--mono); font-size: 11px; }

.pull, .opinion {
  max-width: 38rem;
  margin: 2rem 0;
  padding: 0 0 0 1.1rem;
  border-left: 3px solid var(--jev);
  font-family: var(--serif);
  font-size: 1.35rem;
  line-height: 1.35;
}
.opinion { border-left-color: var(--gold); }
.pair-notes {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.4rem;
  max-width: 54rem;
}
.source, .colophon {
  font-size: 0.88rem;
  color: var(--muted);
}
.limits {
  max-width: 44rem;
  padding-left: 1.1rem;
}
.limits li { margin-bottom: 0.8rem; }
.cta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  margin: 2rem 0 1.5rem;
}
.btn {
  text-decoration: none;
  padding: 0.7rem 1rem;
}
.btn.primary {
  background: var(--ink);
  color: var(--paper);
  border-color: var(--ink);
}
.ink .btn { border-color: color-mix(in srgb, var(--paper) 30%, transparent); }
.ink .btn.primary {
  background: var(--paper);
  color: var(--ink);
  border-color: var(--paper);
}

@media (max-width: 900px) {
  section[id] { scroll-margin-top: 3.6rem; }
  /* No room to the right of the text column at this width; the numeral is decorative,
     and letting it sit outside would push a horizontal scrollbar onto the page. */
  .chapter-no { display: none; }
  .rail {
    position: sticky;
    top: 0;
    inset: auto;
    width: 100%;
    height: auto;
    flex-direction: row;
    align-items: center;
    gap: 0.8rem;
    padding: 0.7rem 1rem;
    border-right: 0;
    border-bottom: 1px solid color-mix(in srgb, var(--paper) 12%, transparent);
  }
  .rail ol {
    flex-direction: row;
    overflow-x: auto;
    gap: 0.9rem;
    flex: 1;
    scrollbar-width: none;
    /* The labels are a single scrolling line here; the fade is the only cue that
       there is more to the right, since the scrollbar is hidden. */
    mask-image: linear-gradient(to right, #000 88%, transparent);
  }
  .rail ol::-webkit-scrollbar { display: none; }
  .rail li { flex: 0 0 auto; }
  .rail a { white-space: nowrap; }
  .rail a span { display: none; }
  .rail-repo { margin-top: 0; }
  main { margin-left: 0; }
  .hero-board, .hero-stats, .split, .pair-notes, .persona { grid-template-columns: 1fr; }
  .hero { padding-top: 2rem; }
}

/* Phone: the page is a long read, so the vertical rhythm tightens rather than the type. */
@media (max-width: 600px) {
  body { font-size: 1rem; }
  .chapter { padding: 3.2rem 6vw 2.6rem; }
  .chapter-head h2 { margin-bottom: 0.6rem; }
  .lede { font-size: 1.05rem; }
  figcaption, .frame > p { font-size: 0.9rem; }
  .frame { padding: 0.9rem 0.9rem 1.1rem; margin-bottom: 1.1rem; }
  .pull, .opinion { margin: 1.4rem 0; }
  .hero-board { margin: 1.6rem 0 1rem; }
}

@keyframes bar-in {
  to { transform: scaleX(1); }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .chart .bar { transform: none !important; animation: none !important; }
}