.book-article {
  font-family: var(--notes-font);
  font-size: calc(var(--body-size) - 1px);
  line-height: 1.6;
  overflow-wrap: anywhere;
}

.book-article iframe {
  max-width: 100%;
}

.book-article h1,
.book-article h2,
.book-article h3,
.book-article h4 {
  font-family: inherit;
  font-weight: 700;
}

.book-article h1 {
  font-size: 2.2rem;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid var(--line);
}

.book-article h2 {
  font-size: 1.8rem;
}

.book-article h3 {
  font-size: 1.5rem;
}

.book-article h4 {
  font-size: 1.3rem;
}

.book-article > .page-header h1 {
  font-size: 20pt;
  font-weight: 300;
  border: 0;
  padding: 0;
}

.book-article .code-header,
.book-article .code-summary,
.book-article .code-output {
  line-height: 1.6;
}

.book-article .code-box .codehilite pre {
  padding-left: 0.3rem;
}

.book-article .code-output pre {
  font: inherit;
  line-height: 1.25;
}

.layout-book .nav {
  display: flex;
  gap: 0.75rem;
  justify-content: space-between;
  margin: 1rem 0 1.5rem;
  padding: 0.5rem 0 0.8rem;
  border-bottom: 1px solid var(--line);
}

.layout-book .nav span {
  display: inline-block;
  border-radius: var(--radius);
  background: var(--surface-alt);
  font-size: 0.9rem;
  font-weight: 500;
  padding: 0.35rem 0.65rem;
}

.layout-book .nav .inactivenav {
  color: var(--muted);
}

@media (max-width: 700px) {
  .layout-book .nav {
    flex-direction: column;
  }
}