:root {
  --text-color: #2c3e50;
  --bg-color: #ffffff;
  --link-color: #2980b9;
  --max-width: 800px;
}
@media (prefers-color-scheme: dark) {
  :root { --text-color: #ecf0f1; --bg-color: #2c3e50; --link-color: #3498db; }
}
body {
  font-family: system-ui, sans-serif;
  line-height: 1.6;
  color: var(--text-color);
  background-color: var(--bg-color);
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 20px;
}
header, footer { padding: 1rem 0; }
a { color: var(--link-color); }
button { padding: 10px 20px; cursor: pointer; }
input { padding: 10px; margin-right: 5px; }
nav { margin-bottom: 2rem; }
@media (prefers-reduced-motion: reduce) { *, *::before, *::after { animation-duration: 0.01ms !important; } }