html {
    background-color:rgb(150,255,150);
}
body {
    width: 400px;
    margin: 0 auto;
    background-color: hotpink;
    padding: 20px 20px 20px 20px;
    border: 5px solid black;
}
div{
    width: 400px;
    height: 400px;
    border: 1px solid black;
    border-radius: 200px;
}