@import url("extra.css");
body {
  margin: 0;
  padding: 0;
}
h1 {
  margin: 0;
  font-size: ;
}
header {
  color: yellow;
  background-color: black;
}
div.rectangle {
  margin: 30px auto;
  width: 300px;
  height: 300px;
  text-align: center;
  color: yellow;
  background-color: black;
}
footer {
  color: yellow;
  background-color: black;
}