a {
  color: #b79500;
}

a:hover {
  animation-name: aHover;
  animation-duration: 0.8s;
  animation-timing-function: ease-in;
  animation-direction: alternate;
  animation-iteration-count: infinite;
}

@keyframes aHover {
  from {
    opacity: 1;
  }
  to {
    opacity: 0.5;
  }
}