body {
  margin: 2rem;
  font-family: system-ui, sans-serif;
  background: #f4f4f4;
  color: #111;
  transition: background 0.3s, color 0.3s;
}

body.dark {
  background: #121212;
  color: #eee;
}

a {
  color: #0066cc;
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

button {
  margin-top: 1rem;
  padding: 0.5rem 1rem;
  cursor: pointer;
}