JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://modernizr.com/downloads/modernizr-latest.js"></script>
<div id="container">
    <div id="flash">Here is the Flash animation</div>
    <div id="css">Here is the CSS animation</div>
</div>

CSS

#container {
    position: relative;
    width: 250px;
    height: 40px;
    background: #dddddd;
}

#container > div {
    position: absolute;
    width: 100%;
    height: 100%;
}

.cssanimations #flash,
#css {
    display: none;
}

.cssanimations #css {
    display: initial;
}