#scroll-to-top {
    display: none;
    position: fixed;
    bottom: 20px;
    right: 20px;
    width: 40px;
    height: 40px;
    background-color: #000;
    border-radius: 50%;
    cursor: pointer;
    z-index: 999;
}

#scroll-to-top:after {
    content: '\2191'; /* Up arrow */
    font-size: 20px;
    color: #fff;
    position: absolute;
    top: 50%;
    left: 50%;
    margin-top: -12px;
    margin-left: -6px;
}