body {
  font-family: sans-serif;
  margin: 0;
}
header {
  background: blue;
  height: 100px;
}
h1 {
  text-align: center;
  color: white;
  line-height: 100px;
  margin: 0;
}
section {
  zoom: 0.8;
}
article {
  padding: 10px;
  margin: 10px;
  background: yellow;
  border: 1px solid navy;
}
footer {
  padding: 10px;
  margin: 10px;
  background: blue;
  color: white;
}
img {
  max-inline-size: 100%;
}
.extra {
  color: maroon;
}
.centered {
  display: block;
  margin-left: auto;
  margin-right: auto;
  width: 95%;
}
/* Add your flexbox CSS below here */