div {
  background-color: lightgrey;
  width: 300px;
  border: 15px solid green;
  padding: 50px;
  margin: 20px;
}
div.tamaño {
  color: rgb(255, 255, 255);
  background-color: rgb(10, 15, 19);
  width: 320px;
  height: 100px;
  padding: 10px;
  border: 10px solid rgb(8, 3, 3);
  margin: 0;
}