#HTML代碼
<div class="box1">
    <div class="box1-content"> &nbsp;</div>
</div>

#CSS代碼

.box1{
	background:#000;
	width:300px;
	height:200px;
}
.box1-content{
    width: 100%;
    height: 100%;
    background: radial-gradient(180px at top right,#685e31,rgba(0,0,0,0)),
        radial-gradient(180px at top left,#0d92c3,rgba(0,0,0,0)),radial-gradient(180px at bottom left,#8a43bd,rgba(0,0,0,0)),radial-gradient(180px at bottom right,#1d8d42,rgba(0,0,0,0));
}