#square{
  height:50px;
  width:50px;
  background-color:#000000;
  animation-name:spin;
  animation-duration:3000ms;
  animation-timing-function:linear;
  animation-iteration-count:infinite;
}
@keyframes spin{
  from{
    transform:rotate3d(1,1,1,0deg);
  }
  to{
   transform:rotate3d(1,1,1,360deg);
  }
}