data/train/codepen-AKOQrA-vELmaP/full.html

<!DOCTYPE html>
<html>
<head>
  <style>.signal {
    border: 5px solid #333;
    border-radius: 30px;
    height: 30px;
    left: 50%;
    margin: -15px 0 0 -15px;
    opacity: 0;
    position: absolute;
    top: 50%;
    width: 30px;
 
    animation: pulsate 1s ease-out;
    animation-iteration-count: infinite;
}

@keyframes pulsate {
    0% {
      transform: scale(.1);
      opacity: 0.0;
    }
    50% {
      opacity: 1;
    }
    100% {
      transform: scale(1.2);
      opacity: 0;
    }
}</style>
</head>
<body>
  <div class="signal"></div>
  <script></script>
</body>
</html>