docs/stylesheets/scroll-button.scss

button.arrow-for-scrolling-top {
    opacity: 0;
    transition: 1s;
    background-color: #0367d6;
    color: #fff;
    position: fixed;
    bottom: 10px;
    right: 10px;
    display: block;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    &.show {
        opacity: 1;
        border: none;
        transition: 1s;
    }
}