* {
  box-sizing: border-box; }

htm, body {
  margin: 0;
  padding: 0; }

header {
  border: 20px solid #000;
  background: yellow;
  min-height: 100vh;
  display: flex; }
  header h1 {
    font-size: 8vw;
    margin: auto; }

article {
  padding: 1em 3em; }

footer {
  text-align: center;
  margin-bottom: 3em; }