:root {
  --bg: #fafafa;
  --fg: #1a1a1a;
  --card-bg: #ffffff;
  --border: #e2e2e2;
  --accent: #2563eb;
  --tag-bg: #eef2ff;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #121212;
    --fg: #f0f0f0;
    --card-bg: #1e1e1e;
    --border: #333333;
    --accent: #60a5fa;
    --tag-bg: #1e293b;
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", system-ui, sans-serif;
  background: var(--bg);
  color: var(--fg);
  line-height: 1.6;
}

.site-header {
  position: sticky;
  top: 0;
  background: var(--bg);
  padding: 1rem;
  border-bottom: 1px solid var(--border);
  z-index: 10;
}

.site-header h1 {
  margin: 0 0 0.75rem;
  font-size: 1.25rem;
}

#search-box {
  width: 100%;
  padding: 0.6rem 0.8rem;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--card-bg);
  color: var(--fg);
  font-size: 1rem;
}

main {
  padding: 1rem;
  max-width: 900px;
  margin: 0 auto;
}

.category-group {
  margin-bottom: 2rem;
}

.category-group h2 {
  font-size: 1.1rem;
  margin-bottom: 0.75rem;
}

.card-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.75rem;
}

@media (min-width: 600px) {
  .card-grid { grid-template-columns: repeat(2, 1fr); }
}

@media (min-width: 900px) {
  .card-grid { grid-template-columns: repeat(3, 1fr); }
}

.card {
  display: block;
  padding: 1rem;
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 10px;
  text-decoration: none;
  color: var(--fg);
}

.card h3 { margin: 0 0 0.5rem; font-size: 1rem; }

.tags { display: flex; flex-wrap: wrap; gap: 0.4rem; margin-bottom: 0.5rem; }

.tag {
  background: var(--tag-bg);
  color: var(--accent);
  padding: 0.15rem 0.5rem;
  border-radius: 999px;
  font-size: 0.75rem;
}

.card time { font-size: 0.8rem; opacity: 0.7; }

#empty-state { text-align: center; opacity: 0.7; padding: 2rem 0; }

.back-link { color: var(--accent); text-decoration: none; font-size: 0.9rem; }

.module-body h2 { margin-top: 2rem; }
.module-body table { width: 100%; border-collapse: collapse; display: block; overflow-x: auto; }
.module-body th, .module-body td { border: 1px solid var(--border); padding: 0.5rem; text-align: left; }
.module-body pre { background: var(--tag-bg); padding: 1rem; border-radius: 8px; overflow-x: auto; }

.meta { font-size: 0.85rem; opacity: 0.7; }