$(document).ready(function() {
$('div').click(function () {
$(this).toggle('fast');
});
});
<body>
<div></div>
</body>
div {
height: 100px;
width: 100px;
border-radius: 100%;
background-color: #000000;
background-image: -webkit-linear-gradient(right, #000000, #ffffff);
background-image: -moz-linear-gradient(right, #000000, #ffffff);
background-image: -ms-linear-gradient(right #000000, #ffffff);
background-image: -o-linear-gradient(right, #000000, #ffffff);
}