#btn-back-to-top {
    width: 50px;
    height: 50px;
    z-index: 10000;
    position: fixed;
    display: none;
    border-radius: 8px !important;
}

.arrow {
    border: solid white;
    border-width: 0 3px 3px 0;
    display: inline-block;
    padding: 5px;
    margin-top: 15px;
}

.up {
    transform: rotate(-135deg);
    -webkit-transform: rotate(-135deg);
}