body {
  font-family: sans-serif;
  margin: 0;
  padding: 20px;
  background: #f4f4f4;
  text-align: center;
}
header {
  background: #333;
  color: white;
  padding: 1em 0;
}
button {
  padding: 10px 20px;
  font-size: 1rem;
  margin-top: 20px;
}
footer {
  margin-top: 40px;
  font-size: 0.9em;
  color: #666;
}