.bck {
    position: fixed;
    bottom: 1rem;
    right: 1rem;
    /* background: rgba(0,0,0,.8); */
    color: #D33B02;
    ;
    visibility: hidden;
    /* width: 50px; */
    /* height: 50px; */
    /* line-height: 50px; */
    text-align: center;
    transition-property: all;
}

.bck.bck-on {
    visibility: visible;
}

.fade {
    opacity: 0;
}

.bck-on.fade {
    opacity: 1;
}

.rightToLeft {
    right: -50px;
}

.bck-on.rightToLeft {
    right: 1rem;
}

.bottomToTop {
    bottom: -50px;
}

.bck-on.bottomToTop {
    bottom: 1rem;
}

.bck-leftToRight {
    left: -50px;
}

.bck-on.leftToRight {
    left: 1rem;
}

.topToBottom {
    top: -50px;
}

.bck-on.topToBottom {
    top: 1rem;
}