.back-to-top,
.back-to-top:active,
.back-to-top:focus,
.back-to-top:visited {
    position:        fixed;
    bottom:          40px;
    right:           40px;
    z-index:         1000;
    width:           50px;
    height:          50px;
    text-align:      center;
    line-height:     48px;
    background:      #000;
    color:           #FFF;
    cursor:          pointer;
    border:          0;
    border-radius:   50%;
    text-decoration: none;
    transition:      opacity 0.2s ease-out;
    opacity:         0;
}

.back-to-top span {
    color: #FFF;
}

.back-to-top.show {
    opacity: 0.6;
}

.back-to-top.show:hover {
    opacity: 1;
}