<div class="circle"></div>
@keyframes fade-out {
    0% { opacity: 1; }
  100% { opacity: 0; }
}

.circle {
  animation: 0.5s fade-out infinite;
  animation-direction: alternate;
}





.circle {
  margin: 50px auto;
  width: 80px;
  height: 80px;
  background: black;
  border-radius: 40px;
}

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.