#boite{
        height: 450px;
        width: 650px;
        position: absolute;
        top: calc(50% - 225px);
        left: calc(50% - 325px);
        z-index : 1;
}


#rectangle{
        height: 400px;
        width: 600px;
        background-color: red;
        position: absolute;
        top: calc(50% - 200px);
        left: calc(50% - 300px);
        z-index : 1;
}
#carre{
        height: 100px;
        width: 100px;
        background-color: blue;
        position : absolute;
        bottom:0;
        right:0;
        z-index : 2;
}
#rond{
        width: 100px;
        height: 100px;
        border-radius: 50px;
        background: yellow;
        position : absolute;
        bottom :-50px;
        left :-50px;
        z-index : 2;
}
#carre2{
        height: 100px;
        width: 100px;
        background-color: green;
        position : absolute;
        top :-25px;
        right :-25px;
        z-index : 0;
}