body {
  font-family: system-ui, sans-serif;
  margin: 0;
  padding: 0;
  background: #f9f9f9;
  color: #333;
}
header {
  background: #222;
  color: white;
  padding: 1rem;
  text-align: center;
}
nav {
  background: #eee;
  padding: 0.5rem;
  text-align: center;
}
nav a {
  margin: 0 1rem;
  color: #222;
  text-decoration: none;
  font-weight: bold;
}
main {
  max-width: 800px;
  margin: 2rem auto;
  padding: 0 1rem;
}