html, body {
    margin: 0;
    padding: 0;
    height: 100%;
    width: 100%;
}

body {
    background-image: url("assets/song-turtle.jpg");
    background-size: cover;       /* fill the screen, crop if needed */
    background-position: center;  /* center the image */
    background-repeat: no-repeat; /* don't tile */
}

.visually-hidden {
    position: absolute;
    left: -9999px;
    width: 1px;
    height: 1px;
    overflow: hidden;
}