.bigbox {
	width:600px;
	height:600px;
	margin:20px auto;
	position:relative;
	background:linear-gradient(to bottom,#00a8ff,#cccccc);
}
.box1,.box2,.box3 {
	position:absolute;
	background:#ffffff;
	transition:0.5s ease;
	text-align:center;
	line-height:100px;
	border-radius:10px;
}
.box1 {
	width:300px;
	height:300px;
	top:150px;
	left:150px;
	z-index:3;
}
.box2 {
	opacity:0.8;
	width:200px;
	height:200px;
	top:100px;
	left:200px;
	z-index:2;
}
.box3 {
	opacity:0.5;
	width:100px;
	height:100px;
	top:50px;
	left:250px;
	z-index:1;
}