* {
    box-sizing: border-box;
}


.box {
    width: 100px;
    height: 100px;
    padding: 20px;
    font-size: 15px;
    text-transform: uppercase;
    color: #FFF;
    position: absolute;
}

.box1 {
    background: #3399FF;
    top: 10px;
    left: 10px;
    z-index: -4;
}

.box2 {
    background: #F9DC5C;
    top: 20px;
    left: 20px;
    z-index: 55;
}
.box3 {
    background: #ED254E;
    top: 30px;
    left: 30px;
    z-index: -2;
}
.box4 {
    background: #C2EABD;
    top: 40px;
    left: 40px;
    z-index: -1;
}