* {
	box-sizing:border-box;
}
nav {
	width:600px;
	margin:auto;
	height:30px;
	position:relative;
	background-color:orange;
	display:flex;
}
nav span {
	display:block;
	height:30px;
	line-height:30px;
	padding:0 10px;
	float:left;
	text-align:center;
	cursor:pointer;
}
nav span {
	z-index:1;
}
nav .bg_red {
	background-color:red;
	color:white;
	width:52px;
	z-index:10;
	margin-right:1px;
}
#leave {
	position:absolute;
	left:0px;
	height:30px;
	background-color:red;
	z-index:1;
}
nav .red {
	background-color:red;
	color:white;
}