<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<style type='text/css'>
div{
100px;
height: 100px;
background: pink;
}
div:hover {
animation: rot 5s linear infinite;
}
@keyframes rot{
form{transform: rotate(0deg)}
to{transform: rotate(360deg)}
}
</style>
</head>
<body>
<div>1</div>
</body>
</html>