<div> <span></span> </div> <div class="center"> <span></span> </div> <div> <span></span> </div>
index.html
* {
margin: 0;
padding: 0;
box-sizing: border-box;
}
body {
background-color: blue;
display: flex;
align-items: center;
height: 100vh;
}
div {
flex: 1 1 25%;
height: 25vw;
border-radius: 100%;
background-color: springgreen;
display: flex;
justify-content: center;
align-items: center;
}
.center {
flex-basis: 50%;
height: 50vw;
}