<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>太极图</title>
<style type="text/css">
*{
margin: 0;
padding: 0;
}
body{
background-color: #ddd;
}
.boxs{
display: flex;
align-items: center;
200px;
height: 200px;
margin: 100px auto;
/* 从上往下各占50%由黑变白的一个过程! */
background: linear-gradient(#000 50%,#fff 50%);
border-radius: 50%
}
/* 接下来用css3伪对象选择符创建内部的两个小圆形，由于<i>标签是弹性布局，
并且设置了align-items:center属性，所以创建的内部元素垂直居中： */
.boxs::before,.boxs::after{
content:"";
display: block;
50%;
height: 50%;
border-radius: 50%;
background: rgb(11, 189, 165);
}
.boxs::before{
background:radial-gradient(#fff 25%, #000 25%);
transform-origin: 0% 50%;
animation-name: move;
animation-duration: 1s;
animation-timing-function: linear;
animation-iteration-count: infinite;
animation-direction: alternate;
}
.boxs::after{
background:radial-gradient(#000 25%, #fff 25%);
transform-origin: 100% 50%;
animation-name: move;
animation-duration: 1s;
animation-timing-function: linear;
animation-delay: -1s;
animation-iteration-count: infinite;
animation-direction: alternate;
}
/* 使用关键帧(@keyframes)和动画属性animation：
创建动画，从原始大小0.7倍变化到1.3倍： */
@keyframes move{
from{
transform: scale(0.7);
}
to{
transform:scale(1.3);
}
}
</style>
</head>
<body>
<i class="boxs"></i>
</body>
</html>