content="Joy Du(飘零雾雨), dooyoe@gmail.com, www.doyoe.com" />
<style>
html,body{margin:0;}
button{position:absolute;}
button#b1{
	top:0;left:50%;
	nav-index:1;
	nav-right:#b2;nav-left:#b4;
	nav-down:#b2;nav-up:#b4;
}
button#b2{
	top:50%;right:0;
	nav-index:2;
	nav-right:#b3;nav-left:#b1;
	nav-down:#b3;nav-up:#b1;
}
button#b3{
	left:50%;bottom:0;
	nav-index:3;
	nav-right:#b4;nav-left:#b2;
	nav-down:#b4;nav-up:#b2;
}
button#b4{
	top:50%;left:0;
	nav-index:4;
	nav-right:#b1;nav-le