#scroll-back {
    display: flex; align-items: center; justify-content: center;
    position: fixed; right: 1rem; bottom: 1rem;
    background-color: rgba(244, 241, 222, 0.9);
    border-radius: 0.4rem;
    width: 3rem; height: 3rem;
    font-family: monospace;
    font-size: 2rem;
    padding-top: 0.7rem;
    cursor: pointer;
    opacity: 0; /* controlled by headerParallax.js */

    -webkit-transition: opacity 0.5s;
    -moz-transition: opacity 0.5s;
    -o-transition: opacity 0.5s;
    transition: opacity 0.5s;
}