*{
	margin: 0;
	padding: 0;
}
ul,ol{
	list-style: none;
}
.out{
	width: 400px;
	height: 300px;
	position: relative;
	margin:100px  auto 0;
}
img{
	width: 400px;
	height: 300px;
}
ul li{
	position: absolute;
	top: 0;
	left: 0;
	display: none;
}
ol{
	position: absolute;
	width: 400px;
	text-align: center;
	bottom: 10px;
}	
ol li{
	line-height: 20px;
	width: 20px;
	height: 20px;
	background-color: #666;
	display: inline-block;
	margin: 0 5px;
	border-radius: 10px;
	color: #fff;
	cursor: pointer;
}
ol li:hover{
	background-color: #a00;
}
.btn{
	position: absolute;
	font-size:40px;
	height: 60px;
	width: 30px;
	background-color: rgba(0,0,0,0.5);
	line-height: 60px;
	text-align: center;
	top: 50%;
	margin-top: -30px;
	color: #fff;
	display: none;
}
.out:hover .btn{
	display: block;
	cursor: pointer;
}
.left{
	left: 0;
}
.right{
	right: 0;
}
.active{
	background-color: #a00;
}