.square {
  margin: 2em;
  background-color: white;
  animation: rotate 2s linear infinite;
}

.container {
  display: flex;
  justify-content: space-between;
}

@keyframes rotate {
  0% {
    width: 4em;
    height: 4em;
  }

  50% {
    width: 8em;
    height: 8em;
    transform: rotate(360deg);
    background-color: aqua;
  }

  100% {
    transform: rotate(360deg);
    width: 4em;
    height: 4em;
  }
}