#scrollTopBtn
{
    position: fixed;
    right: 1.25rem;
    bottom: 1.25rem;
    z-index: 1000;

    width: 44px;
    height: 44px;

    border: none;
    border-radius: 50%;

    background: #333;
    color: #fff;
    font-size: 1.2rem;
    cursor: pointer;

    opacity: 0;
    pointer-events: none;
    transform: translateY(10px);
    transition: opacity .2s ease, transform .2s ease;
}

#scrollTopBtn.is-visible
{
    opacity: 0.85;
    pointer-events: auto;
    transform: translateY(0);
}

#scrollTopBtn:hover
{
    opacity: 1;
}