<html>
<head>
<style>
#myDIV {
margin: auto;
border: 1px solid black;
outline: coral solid 5px;
width: 300px;
height: 300px;
animation: mymove 5s infinite;
}
@keyframes mymove {
50% {outline-width: 50px;}
}
</style>
</head>
<body>
<h1>Animation of outline-width</h1>
<p>Gradually change the outline-width property from 5px to 50px, and back to 5px:<p>
<div id="myDIV"></div>
</body>
</html>