<div class="div-ani3"></div>

// sass 原理即整个圆形定位在不同位置，overflow:hidden
.div-ani3 {
margin-top:90vw;
position: relative;
align-items: center;
min-height: 15vh;
background-color: #f01b5a;
width:30vw;
margin-left:35vw;
margin-bottom:20vw;

&:after {
content: "";
position: absolute;
left: 50%;
min-width: 100vw;
min-height: 100vw;
background-color: #f16369;
animation-name: rotate;
animation-iteration-count: infinite;
animation-timing-function: linear;
}
&:after {
bottom: 1vh;
border-radius: 50%;
transform: translate(-50%, -2%) rotateZ(180deg);
}
}