:root {
  color-scheme: light dark;
  --gap: 1.5rem;
  --card-bg: #ffffff;
  --card-border: #e2e2e2;
  --text: #1a1a1a;
  --muted: #666666;
}

@media (prefers-color-scheme: dark) {
  :root {
    --card-bg: #1e1e1e;
    --card-border: #3a3a3a;
    --text: #f0f0f0;
    --muted: #a0a0a0;
  }
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", sans-serif;
  color: var(--text);
  background: var(--card-bg);
}

.hub-header {
  padding: 3rem 1.5rem 1.5rem;
  text-align: center;
}

.hub-header h1 {
  margin: 0 0 0.5rem;
  font-size: 2.5rem;
}

.hub-tagline {
  margin: 0;
  color: var(--muted);
}

main {
  max-width: 1100px;
  margin: 0 auto;
  padding: 1.5rem;
}

.subsite-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: var(--gap);
}

.subsite-card {
  display: flex;
  flex-direction: column;
  border: 1px solid var(--card-border);
  border-radius: 8px;
  overflow: hidden;
  text-decoration: none;
  color: inherit;
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}

.subsite-card:hover,
.subsite-card:focus-visible {
  transform: translateY(-4px);
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.15);
}

.subsite-card img {
  width: 100%;
  aspect-ratio: 16 / 10;
  object-fit: cover;
  object-position: top;
  background: var(--card-border);
  display: block;
}

.subsite-name {
  padding: 1rem;
  font-weight: 600;
}