.pulse {
  display: block;
  border-radius: 50%;
  cursor: pointer;
  box-shadow: 0 0 0 rgba(20,40,16, 0.4);
  animation: pulse 2s infinite;
}
.pulse:hover {
  animation: none;
}

@-webkit-keyframes pulse {
  0% {
    -webkit-box-shadow: 0 0 0 0 rgba(20,40,16, 0.4);
  }
  70% {
      -webkit-box-shadow: 0 0 0 10px rgba(20,40,16, 0);
  }
  100% {
      -webkit-box-shadow: 0 0 0 0 rgba(20,40,16, 0);
  }
}
@keyframes pulse {
  0% {
    -moz-box-shadow: 0 0 0 0 rgba(20,40,16, 0.4);
    box-shadow: 0 0 0 0 rgba(20,40,16, 0.4);
  }
  70% {
      -moz-box-shadow: 0 0 0 10px rgba(20,40,16, 0);
      box-shadow: 0 0 0 10px rgba(20,40,16, 0);
  }
  100% {
      -moz-box-shadow: 0 0 0 0 rgba(20,40,16, 0);
      box-shadow: 0 0 0 0 rgba(20,40,16, 0);
  }
}