body{
    margin: 0;
    padding: 0;
}
.root{
    position: absolute;
    top: 50%;
    left: 50%;
    margin-top: -100px;
    margin-left: -200px;
}
.main{
    background-color: #ccc;
    width: 400px;
    height: 200px;
}
.left{
    background-color: #fc0;
    width: 50px;
    height: 50px;
    border-radius:0 0 50px 0;
    position: absolute;
    top: 0;
    left: 0;
}
.right{
    background-color: #fc0;
    width: 50px;
    height: 50px;
    border-radius:50px 0 0 0;
    position: absolute;
    bottom: 0;
    right: 0;
}