.topics-index {
  width: min(100%, 1240px);
  margin: 0 auto;
  padding: clamp(1.5rem, 5vw, 4rem) clamp(0.75rem, 3vw, 2rem);
}
.catalog-header { max-width: 780px; margin-bottom: 2.5rem; }
.eyebrow {
  color: var(--learn-accent);
  font-family: "Fira Code", monospace;
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.13em;
  margin-bottom: 0.75rem;
}
.catalog-header h1 {
  font-size: clamp(2.5rem, 6vw, 4.5rem);
  font-weight: 700;
  letter-spacing: -0.055em;
  line-height: 1.1;
  margin-bottom: 1.25rem;
}
.catalog-intro { max-width: 650px; color: var(--learn-muted); font-size: 1.1rem; }
.catalog-meta { color: var(--learn-muted); font-size: 0.85rem; }
.catalog-meta span { margin: 0 0.65rem; color: var(--learn-border); }
.catalog-search { max-width: 680px; margin-bottom: 3rem; }
.catalog-search label { display: block; margin-bottom: 0.65rem; font-size: 0.875rem; font-weight: 600; }
.catalog-search input {
  width: 100%;
  padding: 1rem 1.25rem;
  border: 1px solid var(--learn-border);
  border-radius: 0.5rem;
  background: var(--learn-surface);
  color: var(--learn-text);
  font: inherit;
}
.catalog-search input::placeholder { color: var(--learn-muted); }
.catalog-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(min(100%, 300px), 1fr)); gap: 1.25rem; }
.topic-card {
  min-width: 0;
  padding: clamp(1.25rem, 3vw, 2rem);
  border: 1px solid var(--learn-border);
  border-radius: 0.75rem;
  background: var(--bg-surface, linear-gradient(135deg, #1b252e, var(--learn-surface) 65%));
}
.discipline-section + .discipline-section { margin-top: 3rem; }
.discipline-heading { display: flex; align-items: baseline; justify-content: space-between; flex-wrap: wrap; gap: 0.5rem 1rem; margin-bottom: 1.25rem; }
.discipline-heading h2 { margin: 0; font-size: 1.5rem; letter-spacing: -0.025em; }
.discipline-heading h2 a { color: var(--learn-text); text-decoration: none; }
.discipline-heading h2 a:hover { color: var(--learn-accent); }
.topic-card h2 { margin: 0 0 0.75rem; font-size: 1.4rem; letter-spacing: -0.025em; }
.topic-card h2 a { display: flex; justify-content: space-between; gap: 1rem; color: var(--learn-text); text-decoration: none; overflow-wrap: anywhere; }
.topic-card h2 a span { color: var(--learn-accent); }
.topic-card h2 a:hover { color: var(--learn-accent); }
.topic-preview { list-style: none; padding: 0; margin: 1.25rem 0 0; border-top: 1px solid var(--learn-border); }
.topic-preview li { border-bottom: 1px solid var(--learn-border); }
.topic-preview a { display: block; padding-block: 0.65rem; color: var(--learn-muted); text-decoration: none; font-size: 0.9rem; overflow-wrap: anywhere; }
.topic-preview a:hover { color: var(--learn-accent); }
.view-all { display: inline-block; margin-top: 1.25rem; font-size: 0.85rem; text-decoration: none; }
.article-results { list-style: none; padding: 0; }
.article-results a { display: block; padding: 1rem 0; border-bottom: 1px solid var(--learn-border); text-decoration: none; }
.article-results small { display: block; color: var(--learn-muted); margin-top: 0.3rem; }
#search-heading { font-size: 1.5rem; }
#search-status { color: var(--learn-muted); }