body {
  font-family: sans-serif;
  margin: 0;
  padding: 0;
  background: #f8fafc;
  color: #333;
}
header {
  background: #0ea5e9;
  color: white;
  padding: 2rem;
  text-align: center;
}
main {
  padding: 2rem;
}
article {
  background: white;
  padding: 1rem;
  margin: 1rem auto;
  max-width: 600px;
  border-radius: 8px;
  box-shadow: 0 0 10px rgba(0,0,0,0.1);
}
footer {
  text-align: center;
  padding: 1rem;
  background: #e5e7eb;
}