<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style type="text/css">
body {
background-color:chartreuse;
}
#taiji {
width: 0px;
height: 600px;
border-left: 300px solid royalblue;
border-right: 300px solid darkorange;
border-radius: 100%;
}
#taiji:before {
content: '';
display: block;
width: 100px;
height: 100px;
border: 100px solid royalblue;
border-radius: 100%;
background-color:darkorange;
margin-left: -150px;
}
#taiji:after {
content: '';
display: block;
width: 100px;
height: 100px;
border: 100px solid darkorange;
border-radius: 100%;
background-color:royalblue;
margin-left: -150px;
}
</style>
</head>
<body><div id="taiji"></div>
</body>
</html>