#back-to-top {
    display: none;
    position: fixed;
    bottom: 10px;
    right: 10px;
    background-color: #007BFF !important;
}

#back-to-top a span {
    display: block;
    width: 40px;
    height: 40px;
    background: url("/images/top-arrow.svg") no-repeat center center;
    opacity: 0.5;
    transition-duration: 0.5s
}

#back-to-top a:hover span {
    opacity: 1;
}