#onTopBtn {
    display: none;
    z-index: 9999;
    text-decoration: none;
    font-size: 3rem;
    line-height: 1rem;
    text-align: center;
    width: 4rem;
    height: 4rem;
    border-radius: 32%;
    /*background-color: black;*/
    padding: 0.25rem;
    position: fixed;
    pointer-events: all;
    top: calc(100vh - 10rem);
    left: 50%;
    margin-left: -2rem;
}

/*#onTopBtn .fa-chevron-up {*/
/*    color: yellow;*/
/*}*/