pulse

.element{  
height: 250px;
  width: 250px;
  margin: 0 auto;
  animation-name: stretch;
  animation-duration: 500ms; 
  animation-timing-function: ease; 
  animation-delay: 0;
  animation-direction: alternate;
  animation-iteration-count: infinite;
  animation-fill-mode: none;
  animation-play-state: running;
}
 
@keyframes stretch {
  0% {
    transform: scale(.3);
    border-radius: 100%;
  }
  50% {

  }
  100% {
    transform: scale(1.5);
     position: relative;
    translateX(-50%);
    translateY(-50%);
  }
}