CSS Animatable max-width Property Example

<!DOCTYPE html>
<html>
<head>
<style> 
#outer {
	background: #f00;
    box-shadow: 0 0 10px 0 #aaa;
    padding: 10px;
    max-width: 150px;
    animation: anim-outer 5s infinite;
}
#container {
    display: flex;
    justify-content: center;
    align-items: center;
    color: #fff;
    font-size: 20px;
    width: 100%;
    height: 30px;
    background: #333;
	box-shadow: 0 0 10px 0 #aaa;
    animation: anim 5s infinite;
}
  
@keyframes anim {
  	50% {width: 500px;}
}
@keyframes anim-outer {
  	50% {max-width: 300px;}
}
</style>
</head>
<body>

<h1>Animatable 'max-width' Property</h1>
<hr>
  
<p>Experience the changing max-width of the outer Container.</p>
<div id="outer">
	<div id="container">Container</div>
</div>

</body>
</html>