.book-navigation {
  font-family: Inter, sans-serif;
  padding: 28px 22px;
  background: #fff;
}
.book-navigation-title {
  display: block;
  margin-bottom: 26px;
  color: #343a40;
  font-size: 21px;
  line-height: 1.4;
  text-decoration: none;
}
.book-navigation ul {
  list-style: none;
  margin: 0;
  padding: 0;
}
.book-navigation li { margin-bottom: 12px; }
.book-navigation li a {
  display: block;
  color: #555;
  font-size: 15px;
  line-height: 1.5;
  text-decoration: none;
}
.book-navigation li a:hover,
.book-navigation li a[aria-current="page"] { color: #2563eb; }
@media (min-width: 1200px) {
  .book-navigation {
    position: fixed;
    top: 58px;
    bottom: 0;
    left: 0;
    width: 250px;
    overflow-y: auto;
  }
  #quarto-content { margin-left: 250px; }
}
@media (max-width: 1199px) {
  .book-navigation { border-bottom: 1px solid #e2e8f0; }
  .book-navigation-title { margin-bottom: 14px; }
}