/* Match the existing site's Tabler palette and typography. */
:root {
  --course-blue: #206bc4;
  --course-ink: #1e293b;
  --course-muted: #66758a;
  --course-rule: #dce1e7;
  --course-paper: #ffffff;
}

.course-header,
.course-nav,
.course-footer {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
}

.course-header {
  gap: 1rem 2rem;
  padding-block: 0.6rem;
}

.course-header .navbar-brand {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  margin: 0;
}

.course-nav {
  gap: 1.5rem;
  margin-left: auto;
}

.course-nav a {
  color: var(--course-muted);
  padding-block: 0.6rem;
  border-bottom: 2px solid transparent;
  text-decoration: none;
}

.course-nav a[aria-current="page"] {
  color: var(--course-blue);
  border-color: currentColor;
}

.course-nav a:hover {
  color: var(--course-blue);
}

.course-content {
  padding-top: 1.5rem;
  padding-bottom: 3rem;
}

.course-title {
  margin-bottom: 2.75rem;
}

.course-title h1 {
  color: var(--course-ink);
  font-size: clamp(1.75rem, 4vw, 2.5rem);
  line-height: 1.3;
  margin-bottom: 0.75rem;
}

.course-title p,
.course-help {
  color: var(--course-muted);
  font-size: 1rem;
  line-height: 1.75;
}

#chapter-heading {
  font-size: 1.125rem;
  margin-bottom: 1rem;
}

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

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

.chapter-link {
  display: grid;
  grid-template-columns: 3.5rem minmax(0, 1fr) auto;
  align-items: center;
  gap: 1.5rem;
  padding: 1.75rem 1.25rem;
  color: var(--course-ink);
  text-decoration: none;
  background: var(--course-paper);
  transition: background-color 150ms ease;
}

.chapter-link:hover {
  color: var(--course-ink);
  text-decoration: none;
  background: #f0f5fb;
}

.chapter-number {
  font-family: ui-monospace, SFMono-Regular, Consolas, monospace;
  font-size: 1.75rem;
  color: var(--course-muted);
  font-variant-numeric: tabular-nums;
}

.chapter-title strong,
.chapter-title > span {
  display: block;
}

.chapter-title strong {
  font-size: 1.25rem;
  font-weight: 600;
  line-height: 1.5;
}

.chapter-title > span {
  color: var(--course-muted);
  line-height: 1.75;
  margin-top: 0.3rem;
}

.chapter-action {
  color: var(--course-blue);
  white-space: nowrap;
}

.course-help {
  margin-top: 1.75rem;
  max-width: 48rem;
}

.course-help kbd {
  white-space: nowrap;
}

.course-footer {
  gap: 0.5rem 1.5rem;
  color: var(--course-muted);
}

.course-footer a {
  margin-left: auto;
}

a:focus-visible {
  outline: 3px solid var(--course-blue);
  outline-offset: 4px;
}

.skip-link {
  position: absolute;
  left: 1rem;
  top: 0.75rem;
  transform: translateY(-180%);
  padding: 0.5rem 1rem;
  background: var(--course-paper);
  z-index: 10;
}

.skip-link:focus {
  transform: none;
}

@media (max-width: 640px) {
  .course-nav {
    width: 100%;
    margin-left: 0;
  }

  .course-content {
    padding-top: 0.75rem;
  }

  .chapter-link {
    grid-template-columns: 2.5rem minmax(0, 1fr);
    gap: 0.75rem;
    padding: 1.25rem 0.75rem;
  }

  .chapter-action {
    grid-column: 2;
    margin-top: 0.25rem;
  }

  .course-footer a {
    margin-left: 0;
  }
}

@media (prefers-reduced-motion: reduce) {
  .chapter-link {
    transition: none;
  }
}