:root {
  --bg: #ffffff;
  --fg: #1f2328;
  --muted: #59636e;
  --accent: #0969da;
  --card: #f6f8fa;
  --border: #d1d9e0;
  --max: 52rem;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0d1117;
    --fg: #e6edf3;
    --muted: #9198a1;
    --accent: #4493f8;
    --card: #151b23;
    --border: #3d444d;
  }
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

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

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

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

nav {
  max-width: var(--max);
  margin: 0 auto;
  padding: 0.75rem 1.25rem;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
}

nav .brand { font-weight: 700; color: var(--fg); }

nav ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  gap: 1.25rem;
}

main {
  max-width: var(--max);
  margin: 0 auto;
  padding: 0 1.25rem;
}

section {
  padding: 3rem 0 1rem;
  scroll-margin-top: 3.5rem;
}

h1 { font-size: 2.25rem; margin: 0 0 1rem; }
h2 { font-size: 1.5rem; margin: 0 0 1rem; border-bottom: 1px solid var(--border); padding-bottom: 0.3rem; }
h3 { margin: 0 0 0.5rem; }

.cards {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(15rem, 1fr));
  gap: 1rem;
}

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 1rem 1.25rem;
}

.card p { margin: 0.4rem 0; }
.card .tags { color: var(--muted); font-size: 0.875rem; }
.card .links a { margin-right: 1rem; }

.button {
  display: inline-block;
  padding: 0.4rem 1rem;
  margin-right: 1rem;
  border-radius: 6px;
  background: var(--accent);
  color: #fff;
}
.button:hover { text-decoration: none; opacity: 0.9; }

.pdf {
  width: 100%;
  height: 80vh;
  border: 1px solid var(--border);
  border-radius: 8px;
}

.contact { list-style: none; padding: 0; }
.contact li { margin: 0.35rem 0; }

footer {
  max-width: var(--max);
  margin: 3rem auto 0;
  padding: 1.5rem 1.25rem;
  color: var(--muted);
  font-size: 0.875rem;
  border-top: 1px solid var(--border);
}