nav a:nth-child(5){
	border-bottom: 2px solid white;
}
.introduce{
	width: 760px;
	height: 6800px;
	padding-left: 210px;
	margin: 50px 30px 0 0;
}
.introduce div{
	width: 700px;
	height: 450px;
	color: white;
	margin: 0 auto;
}

.introduce div img{
	width: 700px;
	height: 380px;
	border: 1px solid white;
}
.introduce div span{
	display: inline-block;
	text-indent: 2em;
	line-height: 30px;
	font-size: 18px;
	font-family: "幼圆";
}
.top img{
	position: fixed;
	bottom: 180px;
	right: 55px;
	width: 25px;
	height: 40px;
	border-radius: 5px;
}