body {
  margin: 0;
  padding: 0;
}
h1 {
  margin: 0;
  font-size: 120px;
}
header {
  color: #ffff00;
  background-color: #000000;
}
div.rectangle {
  margin: 30px auto;
  width: 300px;
  height: 300px;
  text-align: center;
  color: #ffff00;
  background-color: #000000;
}
footer {
  color: #ffff00;
  background-color: #000000;
}