body {
  margin: 0;
  padding: 0;
  background: #0a0a0a;
}
a {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 180px;
  height: 60px;
  line-height: 60px;
  text-align: center;
  background: #34eb89;
  color: #fff;
  font-size: 30px;
  text-transform: uppercase;
  text-decoration: none;
  font-family: sans-serif;
  letter-spacing: 4px;
  box-shadow: 0 5px 5px rgba(0,0,0,.2);
  border: 2px solid #34eb89;
  transition: .5s;
}
a:hover {
  background: #fff;
  text-shadow: 0 5px 5px rgba(0,0,0,.5);
}
a::before,
a::after {
  content: '';
  position: absolute;
  width: 54%;
  height: 100%;
  background: #34eb89;
  z-index: -1;
  opacity: 0;
}
a:hover::before {
  opacity: 1;
  top: 5px;
  left: -5px;
  box-shadow: 5px 2px 5px rgba(0,0,0,.2);
  animation: animate 2s linear infinite;
}
a:hover::after {
  opacity: 1;
  top: 5px;
  right: -5px;
  box-shadow: -5px 2px 5px rgba(0,0,0,.2);
  animation: animate 2s linear infinite;
  animation-delay: -1s;
}
@keyframes animate {
  0% {
    top: 5px;
  }
  50% {
    top: -5px;
  }
  100% {
    top: 5px;
  }
}