<link rel="stylesheet" href="//brick.a.ssl.fastly.net/Roboto:400"/>

<div class="button">
  <p>Click me</p>
</div>
body {
  background: #f1c40f;
}

.button {
  background: #3498db;
  width: 180px;
  padding: 4px 0;
  
  position: absolute;
  left: 50%;
  top: 50%;
  transform: translateX(-50%) translateY(-50%);
  border-radius: 3px;

  p {
   	font-family: 'Roboto'; 
	  text-align: center;
  	text-transform: uppercase;
    color: #FFF;
    user-select: none;
  }
  
  &:hover {
    cursor: pointer;
  }
  
  &:after {
    content: "";
    display: block;
    position: absolute;
    width: 100%;
    height: 10%;
    border-radius: 50%;
    background-color: darken(#f1c40f, 20%);
    opacity: 0.4;
    bottom: -30px;
  }
}
View Compiled
var $button = document.querySelector('.button');
$button.addEventListener('click', function() {
  var duration = 0.3,
      delay = 0.08;
  TweenMax.to($button, duration, {scaleY: 1.6, ease: Expo.easeOut});
  TweenMax.to($button, duration, {scaleX: 1.2, scaleY: 1, ease: Back.easeOut, easeParams: [3], delay: delay});
  TweenMax.to($button, duration * 1.25, {scaleX: 1, scaleY: 1, ease: Back.easeOut, easeParams: [6], delay: delay * 3 });
});

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

  1. https://cdnjs.cloudflare.com/ajax/libs/gsap/1.12.1/TweenMax.min.js