:root {
  color-scheme: light dark;
  --ink: #17212b;
  --muted: #526273;
  --paper: #ffffff;
  --page: #edf2f7;
  --panel: #f7fafc;
  --line: #cbd5e1;
  --accent: #005a9c;
  --accent-strong: #003f70;
  --accent-soft: #e6f2fb;
  --warm: #8a4b08;
  --success: #216e39;
  --status-bg: #eaf7ee;
  --shadow: 0 0.35rem 1.4rem rgb(15 23 42 / 10%);
  --measure: 82ch;
}

* {
  box-sizing: border-box;
}

html {
  background: var(--page);
  color: var(--ink);
  font-family: "Segoe UI", "Noto Sans", Arial, sans-serif;
  font-size: 100%;
  line-height: 1.62;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-width: 18rem;
}

a {
  color: var(--accent);
  text-decoration-thickness: 0.09em;
  text-underline-offset: 0.16em;
}

a:hover,
a:focus-visible {
  color: var(--accent-strong);
}

:focus-visible {
  outline: 0.2rem solid #f59e0b;
  outline-offset: 0.18rem;
}

.skip-link {
  background: #111827;
  color: #ffffff;
  left: 1rem;
  padding: 0.7rem 1rem;
  position: fixed;
  top: -5rem;
  z-index: 1000;
}

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

.site-header {
  background: #0d3b5f;
  color: #ffffff;
}

.site-header__inner {
  align-items: center;
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  justify-content: space-between;
  margin: 0 auto;
  max-width: 100rem;
  padding: 0.9rem clamp(1rem, 3vw, 2.5rem);
}

.site-title {
  color: #ffffff;
  font-family: Georgia, "Times New Roman", serif;
  font-size: clamp(1rem, 2vw, 1.3rem);
  font-weight: 700;
  text-decoration: none;
}

.site-header__links {
  align-items: center;
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem;
}

.site-header__link {
  border: 0.08rem solid rgb(255 255 255 / 70%);
  border-radius: 0.35rem;
  color: #ffffff;
  font-size: 0.86rem;
  font-weight: 700;
  padding: 0.34rem 0.62rem;
  text-decoration: none;
}

.site-header__link:hover,
.site-header__link:focus-visible {
  background: #ffffff;
  color: #0d3b5f;
}

.edition-badge,
.course-badge {
  border: 0.08rem solid rgb(255 255 255 / 55%);
  border-radius: 999rem;
  color: #ffffff;
  display: inline-block;
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.03em;
  padding: 0.18rem 0.58rem;
  text-transform: uppercase;
}

.reader-layout {
  display: grid;
  grid-template-columns: minmax(15rem, 20rem) minmax(0, 1fr);
  margin: 0 auto;
  max-width: 100rem;
  min-height: calc(100vh - 4rem);
}

.book-nav {
  align-self: start;
  background: var(--panel);
  border-right: 0.08rem solid var(--line);
  max-height: 100vh;
  overflow: auto;
  padding: 1.35rem 1rem 2rem;
  position: sticky;
  top: 0;
}

.book-nav__title {
  font-size: 0.92rem;
  letter-spacing: 0.04em;
  margin: 0 0 0.7rem;
  text-transform: uppercase;
}

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

.book-nav li + li {
  margin-top: 0.18rem;
}

.book-nav a {
  border-left: 0.22rem solid transparent;
  display: block;
  font-size: 0.9rem;
  line-height: 1.3;
  padding: 0.44rem 0.5rem;
  text-decoration: none;
}

.book-nav a[aria-current="page"] {
  background: var(--accent-soft);
  border-left-color: var(--accent);
  color: var(--accent-strong);
  font-weight: 700;
}

main {
  background: var(--paper);
  box-shadow: var(--shadow);
  min-width: 0;
  padding: clamp(1.2rem, 4vw, 4.2rem);
  width: 100%;
}

.breadcrumbs {
  color: var(--muted);
  font-size: 0.88rem;
  margin: 0 auto 1.6rem;
  max-width: var(--measure);
}

.breadcrumbs ol {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
  list-style: none;
  margin: 0;
  padding: 0;
}

.breadcrumbs li:not(:last-child)::after {
  color: var(--muted);
  content: "/";
  margin-left: 0.35rem;
}

.reader-article {
  margin: 0 auto;
  max-width: var(--measure);
  min-width: 0;
}

.reader-article > h1 {
  color: #173f5f;
  font-family: Georgia, "Times New Roman", serif;
  font-size: clamp(2rem, 5vw, 3.5rem);
  line-height: 1.12;
  margin: 0 0 1rem;
}

.reader-article h2 {
  border-bottom: 0.12rem solid var(--line);
  color: #173f5f;
  font-family: Georgia, "Times New Roman", serif;
  font-size: clamp(1.45rem, 3vw, 2rem);
  line-height: 1.2;
  margin: 3rem 0 1rem;
  padding-bottom: 0.35rem;
}

.reader-article h3 {
  color: #254d6d;
  font-size: 1.2rem;
  margin-top: 2.2rem;
}

.reader-article p,
.reader-article li,
.reader-article dd {
  hanging-punctuation: first last;
  text-wrap: pretty;
}

.reader-article p {
  margin: 0.85rem 0;
}

.reader-article ul,
.reader-article ol {
  padding-left: 1.6rem;
}

.local-toc {
  background: var(--panel);
  border: 0.08rem solid var(--line);
  border-radius: 0.45rem;
  margin: 1.4rem 0 2.2rem;
  padding: 1rem 1.2rem;
}

.local-toc h2 {
  border: 0;
  font-family: inherit;
  font-size: 1rem;
  margin: 0 0 0.4rem;
  padding: 0;
}

.local-toc ol {
  margin: 0;
}

.defn,
.notn,
.conv,
.thm,
.lem,
.prop,
.cor,
.fact,
.exam,
.exer,
.prob,
.proj,
.rem,
.cau,
.proof {
  border-left: 0.28rem solid var(--line);
  margin: 1.4rem 0;
  padding: 0.3rem 1rem 0.55rem 1.15rem;
}

.defn,
.notn,
.conv {
  background: #f1f7fb;
  border-left-color: #2878a9;
}

.thm,
.lem,
.prop,
.cor,
.fact {
  background: #f5f4fb;
  border-left-color: #6957a5;
}

.exam,
.exer,
.prob,
.proj {
  background: #f6faf4;
  border-left-color: #4d7c35;
}

.cau {
  background: #fff7e8;
  border-left-color: #b45309;
}

.proof {
  background: transparent;
  border-left-style: dotted;
}

.environment-title {
  color: var(--ink);
  font-weight: 750;
  margin: 0.3rem 0 0.55rem;
}

.proof::after {
  content: "□";
  display: block;
  font-size: 1.1rem;
  text-align: right;
}

.math.display,
.reader-article math[display="block"] {
  display: block;
  margin: 1rem auto;
  max-width: 100%;
  overflow-x: auto;
  overflow-y: hidden;
  padding: 0.35rem 0;
}

.math-scroll {
  max-width: 100%;
  overflow-x: auto;
  padding: 0.2rem 0;
}

math {
  font-size: 1.02em;
}

table {
  border-collapse: collapse;
  margin: 1.4rem auto;
  max-width: 100%;
  width: 100%;
}

caption {
  color: var(--ink);
  font-weight: 700;
  padding: 0 0 0.45rem;
  text-align: left;
}

th,
td {
  border: 0.08rem solid var(--line);
  padding: 0.55rem 0.65rem;
  text-align: left;
  vertical-align: top;
}

th {
  background: var(--panel);
}

.table-scroll {
  max-width: 100%;
  overflow-x: auto;
}

.diagram {
  background: var(--panel);
  border: 0.08rem solid var(--line);
  border-radius: 0.5rem;
  margin: 1.6rem 0;
  padding: 1rem;
  text-align: center;
}

.diagram svg,
.diagram img {
  height: auto;
  max-width: 100%;
}

.diagram figcaption {
  color: var(--muted);
  margin: 0.8rem auto 0;
  max-width: 70ch;
  text-align: left;
}

.diagram-transcript {
  background: var(--paper);
  border: 0.08rem dashed var(--line);
  margin: 0 auto;
  max-width: 70ch;
  padding: 0.8rem;
  text-align: left;
}

details {
  margin: 0.8rem 0;
}

summary {
  cursor: pointer;
  font-weight: 700;
}

code,
pre,
.source-tex {
  font-family: "Cascadia Mono", Consolas, monospace;
}

pre,
.source-tex {
  background: #111827;
  color: #f8fafc;
  max-width: 100%;
  overflow: auto;
  padding: 0.75rem;
  text-align: left;
  white-space: pre-wrap;
}

.unit-navigation {
  border-top: 0.08rem solid var(--line);
  display: grid;
  gap: 1rem;
  grid-template-columns: 1fr 1fr;
  margin: 3rem auto 0;
  max-width: var(--measure);
  padding-top: 1.2rem;
}

.unit-navigation a {
  background: var(--panel);
  border: 0.08rem solid var(--line);
  border-radius: 0.4rem;
  display: block;
  padding: 0.8rem;
  text-decoration: none;
}

.unit-navigation .next {
  text-align: right;
}

.site-footer {
  background: #0f2940;
  color: #e5eef6;
  font-size: 0.85rem;
  padding: 1.4rem clamp(1rem, 3vw, 2.5rem);
}

.site-footer__inner {
  margin: 0 auto;
  max-width: 96rem;
}

.site-footer a {
  color: #b9e2ff;
}

.status-note {
  background: var(--status-bg);
  border-left: 0.28rem solid var(--success);
  margin: 1rem 0;
  padding: 0.8rem 1rem;
}

.external-url-text {
  overflow-wrap: anywhere;
  word-break: break-word;
}

.index-list {
  columns: 2 22rem;
  column-gap: 2.2rem;
  list-style: none;
  padding: 0;
}

.index-list > li {
  break-inside: avoid;
  margin-bottom: 0.65rem;
}

.index-occurrences {
  font-size: 0.88em;
}

.visually-hidden {
  clip: rect(0 0 0 0);
  clip-path: inset(50%);
  height: 1px;
  overflow: hidden;
  position: absolute;
  white-space: nowrap;
  width: 1px;
}

@media (max-width: 58rem) {
  .reader-layout {
    display: block;
  }

  .book-nav {
    border-bottom: 0.08rem solid var(--line);
    border-right: 0;
    max-height: none;
    position: static;
  }

  .book-nav ol {
    display: grid;
    gap: 0.2rem;
    grid-template-columns: repeat(auto-fit, minmax(12rem, 1fr));
  }

  main {
    box-shadow: none;
  }
}

@media (max-width: 36rem) {
  html {
    font-size: 95%;
  }

  .site-header__inner {
    align-items: flex-start;
    flex-direction: column;
  }

  .site-header__links {
    align-items: stretch;
    flex-direction: column;
    width: 100%;
  }

  main {
    padding: 1.1rem;
  }

  .reader-article math[display="inline"] {
    display: inline-block;
    max-width: 100%;
    overflow-x: auto;
    overflow-y: hidden;
    vertical-align: middle;
  }

  .unit-navigation {
    grid-template-columns: 1fr;
  }

  .unit-navigation .next {
    text-align: left;
  }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
}

@media (prefers-color-scheme: dark) {
  :root {
    --ink: #e5edf5;
    --muted: #afbdca;
    --paper: #101820;
    --page: #09121a;
    --panel: #17232d;
    --line: #415161;
    --accent: #78c7ff;
    --accent-strong: #b6e1ff;
    --accent-soft: #173d58;
    --success: #6fcd8c;
    --status-bg: #173427;
  }

  .defn,
  .notn,
  .conv,
  .thm,
  .lem,
  .prop,
  .cor,
  .fact,
  .exam,
  .exer,
  .prob,
  .proj,
  .cau {
    background: #17232d;
  }

  .reader-article > h1,
  .reader-article h2,
  .reader-article h3 {
    color: #b6e1ff;
  }

  .diagram img {
    filter: invert(1) hue-rotate(180deg);
  }
}

@media print {
  .book-nav,
  .skip-link,
  .unit-navigation {
    display: none;
  }

  .reader-layout {
    display: block;
  }

  main {
    box-shadow: none;
    padding: 0;
  }

  a {
    color: inherit;
  }

  .diagram img {
    filter: none;
  }
}