圆环效果图
.div{
width: 100px;
height: 100px;
background-color: #fbc2eb;
border-radius: 50%;
}
.div:after{
content: " ";
display: block;
width: 50px;
height: 50px;
border-radius: 50%;
background-color: #fff;
position: relative;
top: 25px;
left: 25px;
}