body {
    background: #bbb;
}

#z0 {
    position: absolute;
    top: 0px;
    left: 0px;
    z-index: 0;
}

#z1 {
    position: absolute;
    top: 0px;
    left: 0px;
    z-index: 1;
}

#z2 {
    position: absolute;
    top: 0px;
    left: 0px;
    z-index: 2;
    cursor: pointer;
}