@keyframes swirl {
  from {transform: rotate(0deg) translateX(150px)    rotate(0deg); }
  to { transform: rotate(360deg) translateX(150px)    rotate(-360deg); }
}
#constraints
{ height: 400px;
  width: 400px;
  border: 1px solid black; }
#square
{ top: 175px;
  left: 175px;
  position: relative;
  height: 50px;
  width: 50px;
  background: blue;
  -webkit-animation: swirl 4s linear infinite;
}