:root {
  color-scheme: light;
  --font-body: Georgia, "Times New Roman", serif;
  --font-display: Georgia, "Times New Roman", serif;
  --font-ui: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  --page-width: 49rem;
  --body-size: 1.08rem;
  --body-line: 1.72;
  --section-space: 3.75rem;
  --reader-bg: #edf0f2;
  --page-bg: #ffffff;
  --ink: #202326;
  --muted: #5d666c;
  --rule: #cbd1d5;
  --accent: #8b3042;
  --accent-dark: #632131;
  --link: #166a70;
  --quick-bg: #eef6f6;
  --quick-border: #277a7a;
  --key-bg: #f1f5ed;
  --key-border: #507c48;
  --warning-bg: #fff5e8;
  --warning-border: #b36b18;
  --case-bg: #f4f1f7;
  --case-border: #755388;
  --side-bg: #edf3f8;
  --side-border: #3f7298;
  --history-bg: #f7f1ed;
  --history-border: #9a5a3c;
  --study-bg: #eef5ef;
  --study-border: #3e7653;
  --radius: 4px;
  --page-shadow: 0 10px 30px rgb(34 45 52 / 10%);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: 6rem;
}

body {
  margin: 0;
  background: var(--reader-bg);
  color: var(--ink);
  font-family: var(--font-body);
  font-size: var(--body-size);
  line-height: var(--body-line);
}

a {
  color: var(--link);
  text-decoration-thickness: .08em;
  text-underline-offset: .18em;
}

a:hover {
  color: var(--accent-dark);
}

button,
a {
  -webkit-tap-highlight-color: transparent;
}

:focus-visible {
  outline: 3px solid #2074b8;
  outline-offset: 3px;
}

.reader-bar {
  position: sticky;
  z-index: 20;
  top: 0;
  display: grid;
  grid-template-columns: minmax(12rem, 1fr) auto minmax(8rem, 1fr);
  align-items: center;
  gap: 1rem;
  min-height: 4.25rem;
  padding: .65rem 1.5rem;
  border-bottom: 1px solid var(--rule);
  background: rgb(255 255 255 / 96%);
  font-family: var(--font-ui);
  line-height: 1.25;
}

.book-title {
  color: var(--ink);
  font-size: .97rem;
  font-weight: 700;
  text-decoration: none;
}

.chapter-position {
  margin: 0;
  color: var(--muted);
  font-size: .82rem;
  text-align: right;
}

.style-switcher {
  display: grid;
  grid-template-columns: repeat(3, minmax(5.5rem, 1fr));
  border: 1px solid var(--rule);
  border-radius: 6px;
  background: #f5f6f7;
  overflow: hidden;
}

.style-switcher button {
  min-height: 2.25rem;
  padding: .4rem .7rem;
  border: 0;
  border-right: 1px solid var(--rule);
  background: transparent;
  color: #3e464b;
  font: 650 .78rem/1 var(--font-ui);
  cursor: pointer;
}

.style-switcher button:last-child {
  border-right: 0;
}

.style-switcher button[aria-pressed="true"] {
  background: var(--accent);
  color: #ffffff;
}

.reader-shell {
  display: grid;
  grid-template-columns: minmax(12rem, 17rem) minmax(0, 1fr);
  gap: 2.5rem;
  max-width: 86rem;
  margin: 0 auto;
  padding: 2.5rem 2rem 5rem;
}

.chapter-nav {
  position: sticky;
  top: 6.5rem;
  align-self: start;
  padding: .5rem 0;
  font-family: var(--font-ui);
  font-size: .87rem;
  line-height: 1.4;
}

.nav-label {
  margin: 0 0 .75rem;
  color: var(--muted);
  font-size: .72rem;
  font-weight: 750;
  letter-spacing: 0;
  text-transform: uppercase;
}

.chapter-nav ol {
  margin: 0;
  padding: 0;
  list-style: none;
  border-top: 1px solid var(--rule);
}

.chapter-nav li {
  border-bottom: 1px solid var(--rule);
}

.chapter-nav a {
  display: block;
  padding: .7rem .25rem;
  color: var(--muted);
  text-decoration: none;
}

.chapter-nav a:hover {
  color: var(--accent-dark);
}

main {
  min-width: 0;
}

.chapter {
  width: min(100%, var(--page-width));
  margin: 0 auto;
  padding: 4.5rem 5.25rem 3.5rem;
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  background: var(--page-bg);
  box-shadow: var(--page-shadow);
}

.chapter-header {
  margin-bottom: 4.25rem;
}

.chapter-opening-layout {
  display: block;
}

.chapter-header--visual .chapter-opening-layout {
  display: grid;
  grid-template-columns: minmax(0, 1.15fr) minmax(15rem, .85fr);
  gap: 2.4rem;
  align-items: center;
}

.chapter-heading {
  min-width: 0;
}

.chapter-opening-visual {
  position: relative;
  display: grid;
  min-width: 0;
  min-height: 14.5rem;
  place-items: center;
  margin: 0;
  overflow: hidden;
  border: 1px solid var(--rule);
  background: #f7f8f7;
}

.chapter-opening-visual .opening-grid {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  color: var(--rule);
  opacity: .55;
}

.chapter-opening-visual .opening-grid path {
  fill: none;
  stroke: currentColor;
  stroke-width: 1;
  vector-effect: non-scaling-stroke;
}

.chapter-opening-visual img {
  position: relative;
  z-index: 1;
  width: calc(100% - 2.2rem);
  height: 11.6rem;
  object-fit: contain;
  padding: .6rem;
  background: rgb(255 255 255 / 94%);
}

.chapter-opening-visual figcaption {
  position: relative;
  z-index: 1;
  width: 100%;
  margin: 0;
  padding: .55rem .75rem;
  border-top: 1px solid var(--rule);
  background: var(--page-bg);
  color: var(--muted);
  font-family: var(--font-ui);
  font-size: .7rem;
  line-height: 1.35;
}

.chapter-number {
  margin: 0 0 .7rem;
  color: var(--accent);
  font-family: var(--font-ui);
  font-size: .78rem;
  font-weight: 800;
  letter-spacing: 0;
  text-transform: uppercase;
}

h1,
h2,
h3 {
  color: var(--ink);
  font-family: var(--font-display);
  font-weight: 700;
  letter-spacing: 0;
}

h1 {
  max-width: 15ch;
  margin: 0;
  font-size: 3.1rem;
  line-height: 1.08;
}

.chapter-deck {
  max-width: 38rem;
  margin: 1.45rem 0 0;
  color: var(--muted);
  font-size: 1.27rem;
  line-height: 1.55;
}

.chapter-meta {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
  margin: 2.2rem 0 0;
  padding-top: 1.1rem;
  border-top: 1px solid var(--rule);
  font-family: var(--font-ui);
  font-size: .84rem;
  line-height: 1.45;
}

.chapter-meta div {
  min-width: 0;
}

.chapter-meta dt {
  color: var(--muted);
  font-size: .68rem;
  font-weight: 750;
  text-transform: uppercase;
}

.chapter-meta dd {
  margin: .3rem 0 0;
}

section + section {
  margin-top: var(--section-space);
}

h2 {
  margin: 0 0 1.25rem;
  padding-bottom: .55rem;
  border-bottom: 2px solid var(--accent);
  font-size: 1.72rem;
  line-height: 1.25;
}

h3 {
  margin: 0;
  font-size: 1.12rem;
  line-height: 1.32;
}

p {
  margin: 0 0 1.15rem;
}

.lead {
  font-size: 1.23rem;
  line-height: 1.55;
}

.semantic-block {
  margin: 1.9rem 0;
  padding: 1.15rem 1.3rem 1.2rem;
  border: 1px solid var(--block-border);
  border-left-width: 5px;
  border-radius: var(--radius);
  background: var(--block-bg);
}

.semantic-block .block-label {
  margin: 0 0 .3rem;
  color: var(--block-border);
  font-family: var(--font-ui);
  font-size: .68rem;
  font-weight: 800;
  letter-spacing: 0;
  text-transform: uppercase;
}

.semantic-block h3 {
  margin-bottom: .45rem;
}

.semantic-block p:last-child {
  margin-bottom: 0;
}

.quickconcept {
  --block-bg: var(--quick-bg);
  --block-border: var(--quick-border);
}

.keypoint {
  --block-bg: var(--key-bg);
  --block-border: var(--key-border);
}

.warning {
  --block-bg: var(--warning-bg);
  --block-border: var(--warning-border);
}

.casestudy {
  --block-bg: var(--case-bg);
  --block-border: var(--case-border);
}

.sideline {
  --block-bg: var(--side-bg);
  --block-border: var(--side-border);
}

.historicalnote {
  --block-bg: var(--history-bg);
  --block-border: var(--history-border);
}

.studyandlearn {
  --block-bg: var(--study-bg);
  --block-border: var(--study-border);
}

table {
  width: 100%;
  margin: 2rem 0;
  border-collapse: collapse;
  font-family: var(--font-ui);
  font-size: .88rem;
  line-height: 1.45;
}

caption {
  margin-bottom: .65rem;
  color: var(--ink);
  font-family: var(--font-display);
  font-size: 1.02rem;
  font-weight: 700;
  text-align: left;
}

th,
td {
  padding: .75rem .7rem;
  border-bottom: 1px solid var(--rule);
  text-align: left;
  vertical-align: top;
}

thead th {
  border-top: 2px solid var(--ink);
  border-bottom: 1px solid var(--ink);
  color: var(--muted);
  font-size: .72rem;
  text-transform: uppercase;
}

tbody th {
  width: 24%;
}

.equation {
  display: flex;
  align-items: baseline;
  justify-content: center;
  gap: .75rem;
  margin: 2rem 0;
  padding: 1.1rem;
  border-block: 1px solid var(--rule);
  font-family: var(--font-ui);
}

.equation span {
  color: var(--muted);
  font-size: .88rem;
}

.equation strong {
  color: var(--accent-dark);
  font-family: var(--font-display);
  font-size: 1.45rem;
}

.econ-figure {
  margin: 2.25rem auto;
}

.econ-figure__viewport {
  width: 100%;
}

.econ-figure img {
  display: block;
  width: 100%;
  height: auto;
}

.econ-figure figcaption {
  margin-top: .75rem;
  color: var(--muted);
  font-family: var(--font-ui);
  font-size: .84rem;
  line-height: 1.5;
}

.figure-description {
  margin-top: .8rem;
  border-top: 1px solid var(--rule);
  font-family: var(--font-ui);
  font-size: .82rem;
}

.figure-description summary {
  padding: .55rem 0;
  color: var(--link);
  cursor: pointer;
  font-weight: 700;
}

.figure-description p {
  margin: 0;
  padding: 0 0 .7rem;
  color: var(--muted);
}

.chapter-footer {
  margin-top: 4rem;
  padding-top: 1rem;
  border-top: 1px solid var(--rule);
  color: var(--muted);
  font-family: var(--font-ui);
  font-size: .74rem;
}

.chapter-footer p {
  margin: 0;
}

@media (max-width: 980px) {
  .reader-shell {
    display: block;
    padding: 1.5rem 1rem 4rem;
  }

  .chapter-nav {
    display: none;
  }
}

@media (max-width: 700px) {
  .reader-bar {
    grid-template-columns: 1fr;
    gap: .55rem;
    padding: .7rem 1rem;
  }

  .book-title,
  .chapter-position {
    display: none;
  }

  .style-switcher {
    width: 100%;
  }

  .chapter {
    padding: 2.75rem 1.25rem 2.5rem;
    border-inline: 0;
    box-shadow: none;
  }

  h1 {
    font-size: 2.25rem;
  }

  .chapter-deck {
    font-size: 1.12rem;
  }

  .chapter-meta {
    grid-template-columns: 1fr;
    gap: .9rem;
  }

  .chapter-header--visual .chapter-opening-layout {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }

  .chapter-opening-visual {
    min-height: 12.5rem;
  }

  .chapter-opening-visual img {
    height: 10rem;
  }

  .equation {
    align-items: center;
    flex-direction: column;
    gap: .25rem;
  }

  table {
    display: block;
    overflow-x: auto;
  }
}

@media print {
  body {
    background: #ffffff;
  }

  .reader-bar,
  .chapter-nav {
    display: none;
  }

  .reader-shell {
    display: block;
    max-width: none;
    padding: 0;
  }

  .chapter {
    width: 100%;
    max-width: none;
    padding: 0;
    border: 0;
    box-shadow: none;
  }
}