<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>奥运五环</title>
<style type="text/css">
body{
margin: 20px;
background-color: #efefef;
}
ul.flag{
list-style: none;
position: relative;
margin: 20px auto;
}
.flag li,.flag li:before,.flag li:after{
-webkit-border-radius: 6em;
-moz--border-radius: 6em;
border-radius: 6em;
position: absolute;
}
.flag li{
width: 12em;
height: 12em;
left: 0;
top: 0;
font-size: 1em;
}
.flag li:after{
display: block;
content: "";
top: -0.1em;
left: -0.1em;
right: -0.1em;
bottom: -0.1em;
border: solid 1.4em black;
}
.flag .blue{z-index: 10;left:0;top: 0;}
.flag .yellow{z-index: 20;left: 6.8em;top: 5.7em;}
.flag .black{z-index: 21; left: 13.6em;top: 0;}
.flag .green{z-index: 20; left: 20.4em;top: 5.7em;}
.flag .red{z-index: 10;left: 27.2em;top: 0px;} .flag .blue:after{border-color: blue;}
.flag .yellow:after{border-color: yellow;}
.flag .black:after{border-color: black;}
.flag .green:after{border-color: green;}
.flag .red:after{border-color: red;} /*蓝色压住黄色*/
.flag .blue.alt {z-index: 24;}
.flag .blue.alt, .flag .blue.alt:before, .flag .blue.alt:after{
border-top-color: transparent;
border-left-color: transparent;
border-bottom-color: transparent;
}
/* 黄色压住黑色 */
.flag .yellow.alt { z-index: 23; }
.flag .yellow.alt, .flag .yellow.alt:before, .flag .yellow.alt:after {
border-right-color: transparent;
border-left-color: transparent;
border-bottom-color: transparent;
}
/* 绿色压住黑色 */
.flag .green.alt { z-index: 23; }
.flag .green.alt,.flag .green.alt:before,.flag .green.alt:after {
border-top-color: transparent;
border-right-color: transparent;
border-bottom-color: transparent;
}
/* 红色压住绿色 */
.flag .red.alt { z-index: 23; }
.flag .red.alt, .flag .red.alt:before,.flag .red.alt:after {
border-top-color: transparent;
border-right-color: transparent;
border-left-color: transparent;
}
</style>
</head>
<body>
<ul class="flag">
<li class="blue"></li>
<li class="blue alt"></li>
<li class="yellow"></li>
<li class="yellow alt"></li>
<li class="black"></li>
<li class="green"></li>
<li class="green alt"></li>
<li class="red"></li>
<li class="red alt"></li>
</ul>
</body>
</html>