.wrapper {
  height: 100%;
  display: flex;
  flex-direction: column;
  width: 100%;
  max-width: 50em;
  margin: auto;
  background-color: #f0f0f0;
  color: #333
}
header,footer {
  background-color: #333;
  color: white;
  text-align: center;
  padding: 1em;
}
main {
  flex: 1;
  padding: 2em;
}