body {
  background-color: #FFAB57;
}

img {
  animation-name: brainthrob;
  animation-duration: 1s;
  animation-iteration-count: infinite;
  animation-direction: alternate;
}

.centered {
  border-radius: 1em;
  padding: 1em;
  position: absolute;
  top: 50%;
  left: 50%;
  margin-right: -50%;
  transform: translate(-50%, -50%);
}

@keyframes brainthrob {
  from {
    width: 20em;
    height: 20em;
  }

  to {
    width: 40em;
    height: 40em;
  }
}