:root {
  --bg-color: #ffffff;
  --text-color: #1a1a1a;
  --link-color: #0066cc;
  --link-hover: #004499;
  --border-color: #e0e0e0;
  --secondary-text: #666666;
  --code-bg: #f5f5f5;
  --card-shadow: rgba(0,0,0,0.1);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg-color: #1a1a1a;
    --text-color: #f0f0f0;
    --link-color: #66b3ff;
    --link-hover: #99ccff;
    --border-color: #333333;
    --secondary-text: #a0a0a0;
    --code-bg: #2a2a2a;
    --card-shadow: rgba(0,0,0,0.5);
  }
}

* {
  box-sizing: border-box;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
  background-color: var(--bg-color);
  color: var(--text-color);
  line-height: 1.6;
  margin: 0;
  padding: 0;
  transition: background-color 0.3s ease, color 0.3s ease;
}

header, main, footer {
  max-width: 800px;
  margin: 0 auto;
  padding: 1rem 2rem;
}

header {
  padding-top: 3rem;
  padding-bottom: 2rem;
  border-bottom: 1px solid var(--border-color);
}

h1 {
  font-size: 2.5rem;
  margin: 0;
  font-weight: 700;
  letter-spacing: -0.02em;
}

p.lead {
  font-size: 1.25rem;
  color: var(--secondary-text);
  margin-top: 0.5rem;
}

a {
  color: var(--link-color);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
  color: var(--link-hover);
}

ul {
  list-style: none;
  padding: 0;
}

li {
  margin-bottom: 0.75rem;
}

.card-list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1.5rem;
  margin-top: 2rem;
}

.card {
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 1.5rem;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.card:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 12px var(--card-shadow);
}

.card h2 {
  margin-top: 0;
  font-size: 1.25rem;
}

.card p {
  margin-bottom: 0;
  color: var(--secondary-text);
  font-size: 0.95rem;
}

footer {
  margin-top: 4rem;
  padding-top: 2rem;
  padding-bottom: 2rem;
  border-top: 1px solid var(--border-color);
  color: var(--secondary-text);
  font-size: 0.875rem;
  text-align: center;
}