Return! :)

Z-Index

Z-Index: only works if the element you are trying to style has a non-static position /a defined position

red

yellow

blue

                    
.red, .yellow, .blue{
    height: 200px;
    width: 200px;
    border: 1px solid fuchsia;
    position: absolute;
}
.red{
    background-color: red;
    z-index: 1;
}
.yellow{
    background-color: yellow;
    top: 40px;
    left: 40px;
}
.blue{
    background-color: blue;
    z-index: -1;
    top: 80px;
    left: 80px;
}