#cercle{
    width: 100px;
    height: 100px;
    border-radius: 50px;
    background: red;
    margin : 0;
    display:inline-block;
}
#cercle1{
    width: 100px;
    height: 100px;
    border-radius: 50px;
    background: orange;
    margin: 0;
    float: right ;
    display : inline-block;
}

#cercle2{
    width: 100px;
    height: 100px;
    border-radius: 50px;
    background: blue;
    margin : 0;
    display : inline-block;
    position: absolute;
	bottom: 0;
	left: 0;
}
#cercle3{
    width: 100px;
    height: 100px;
    border-radius: 50px;
    background: green;
    margin : 0;
    display : inline-block;
    position: absolute;
	bottom: 0;
	right: 0;
}
#carre{
    width: 100px;
    height: 100px;
    background-color:violet;
    position: absolute;
    top: calc(50% - 50px);
    left: calc(50% - 50px);
    z-index : 0;
}
#cercle4{
    width: 100px;
    height: 100px;
    border-radius: 50px;
    background-color: black;
    position: absolute;
    top: calc(50% - 50px);
    left: calc(50% - 50px);
    z-index : 1;
}