css:
.bound{
background-color: #3EAAF2;
width: 300px;
height: 100px;
display: flex;
flex-direction: column;
align-items: center;
position: relative;//设置定位
}
.bound::before{
content: "";
width: 40px;
height: 40px;
border-radius: 50%;
display: block;
background: #fff;
position: absolute;
top:50%;
left: -20px;
transform:translateY(-50%);
}
.bound::after{
content: "";
width: 40px;
height: 40px;
border-radius: 50%;
display: block;
background: #fff;
position: absolute;
top:50%;
right: -20px;
transform:translateY(-50%);
}
html:
<div class="bound"></div>