Animating Twitter BootStrap Icons

This uses CSS animation keyframes to animate an icon author(s): Elijah Manor

HTML

<script src="//netdna.bootstrapcdn.com/twitter-bootstrap/2.2.2/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="//netdna.bootstrapcdn.com/twitter-bootstrap/2.2.2/css/bootstrap-combined.min.css">
<script src="//cdnjs.cloudflare.com/ajax/libs/prefixfree/1.0.7/prefixfree.min.js"></script>
<div class="img_container">
  <i class="icon-play-circle"></i>
</div>
<br>
<div class="img_container2">
  <i class="icon-play-circle"></i>
</div>

CSS

.img_container, .img_container2 {
    text-align: center;
    height:100px;
    border:2px solid black;
}
.img_container2{
    height:30px;
}
.img_container > i, .img_container2 > i {
    position:relative;
    top: calc(50% - 10px); /* 50% - 3/4 of icon height */
}