body {
  font-family: Arial, sans-serif;
  margin: 0;
  padding: 0;
  background: #111;
  color: #fff;
}
header, footer {
  background: #222;
  padding: 1rem;
  text-align: center;
}
main {
  padding: 1rem;
}
section {
  margin-bottom: 2rem;
}
iframe {
  border: none;
}