body {
  font-size: 12px;
  font-family: Arial, Helvetica, sans-serif;
  margin: 0;
  padding: 0;
}

header {
  background: rgb(100, 100, 100);
  padding: 16px;
}

main {
  padding: 16px;
}

footer {
  background: rgb(100, 100, 100);
  padding: 16px;
}