:root {
  color-scheme: light dark;
  font-family: "Noto Serif", "Source Serif 4", Georgia, serif;
  line-height: 1.66;
  --page: #f6f3ec;
  --ink: #20262b;
  --heading: #17375e;
  --link: #24518c;
  --rule: #77629a;
  --definition: #eee8f5;
  --definition-border: #8b6ba8;
  --note: #e9f0f7;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  padding: 2.25rem clamp(1rem, 4vw, 4rem) 4rem;
  background: var(--page);
  color: var(--ink);
}

main,
body > header,
body > nav {
  width: min(100%, 66rem);
  margin-inline: auto;
}

.skip-link {
  position: absolute;
  top: -6rem;
  left: 1rem;
  z-index: 20;
  padding: 0.7rem 0.95rem;
  background: #fff;
  color: #111;
  border: 0.15rem solid #111;
}

.skip-link:focus {
  top: 1rem;
}

h1,
h2,
h3,
h4 {
  color: var(--heading);
  line-height: 1.22;
  text-wrap: balance;
}

h1 {
  margin-top: 0.5rem;
  padding-bottom: 0.4rem;
  border-bottom: 0.16rem solid var(--rule);
}

h2,
h3 {
  margin-top: 2.2em;
}

p,
li {
  text-wrap: pretty;
}

a {
  color: var(--link);
  text-underline-offset: 0.16em;
}

a:focus-visible {
  outline: 0.18rem solid #d27d00;
  outline-offset: 0.16rem;
}

.edition-note,
.attribution {
  margin-block: 1.4rem;
  padding: 0.9rem 1.05rem;
  background: var(--note);
  border-left: 0.32rem solid #547ca2;
}

.definition {
  margin-block: 1.5rem;
  padding: 0.95rem 1.1rem;
  background: var(--definition);
  border: 0.12rem solid var(--definition-border);
  border-radius: 0.45rem;
}

.definition > :first-child {
  margin-top: 0;
}

.definition > :last-child {
  margin-bottom: 0;
}

figure {
  margin: 1.6rem auto;
  width: min(100%, 56rem);
}

figure img {
  display: block;
  width: auto;
  max-width: 100%;
  height: auto;
  margin-inline: auto;
}

.numbered-equation {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: center;
  gap: 0.75rem;
  margin-block: 1rem;
  max-width: 100%;
}

.numbered-equation > math {
  display: block;
  margin-inline: auto;
  max-width: 100%;
  overflow-x: auto;
  overflow-y: hidden;
}

.equation-number {
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
}

figcaption {
  margin-top: 0.55rem;
  font-size: 0.94rem;
  text-align: center;
}

.equation,
math[display="block"] {
  max-width: 100%;
  overflow-x: auto;
  padding-block: 0.25rem;
}

.unit-navigation {
  margin-top: 2.5rem;
  padding-top: 0.9rem;
  border-top: 0.1rem solid var(--rule);
}

.rights-boundary {
  margin-top: 2.5rem;
  font-size: 0.94rem;
}

@media (prefers-color-scheme: dark) {
  :root {
    --page: #171a1d;
    --ink: #edf0f2;
    --heading: #bdd7ff;
    --link: #afd0ff;
    --rule: #a38ac7;
    --definition: #2b2535;
    --definition-border: #a88bc2;
    --note: #202c38;
  }
}

@media (max-width: 42rem) {
  body {
    padding: 1rem 1rem 2.5rem;
  }

  h1 {
    font-size: 1.7rem;
  }

  h2 {
    font-size: 1.4rem;
  }
}

@media print {
  :root {
    color-scheme: light;
  }

  body {
    padding: 0;
    background: #fff;
    color: #000;
  }

  .skip-link,
  .unit-navigation {
    display: none;
  }
}

/* Unit 02 semantic blocks extend the verified Unit 01 visual system. */
.theorem,
.remark,
.example {
  margin-block: 1.5rem;
  padding: 0.95rem 1.1rem;
  border-left: 0.32rem solid var(--definition-border);
  background: color-mix(in srgb, var(--definition) 62%, transparent);
}

.proof {
  margin-block: 1.5rem;
  padding-left: 1rem;
  border-left: 0.16rem solid var(--rule);
}

.theorem > :first-child,
.remark > :first-child,
.example > :first-child,
.proof > :first-child {
  margin-top: 0;
}

.theorem > :last-child,
.remark > :last-child,
.example > :last-child,
.proof > :last-child {
  margin-bottom: 0;
}