@media (min-width: 900px) { /* wide screens */
    html body {
        background-image: linear-gradient(
            to right,
            rgba(255,255,255,.49) 0%,
            rgba(255,255,255,.58) calc( 50% - 450px ),
            rgba(255,255,255,.58) calc( 50% - 400px ),
            rgba(255,255,255,.58) calc( 50% + 400px ),
            rgba(255,255,255,.58) calc( 50% + 450px ),
            rgba(255,255,255,.49) 100%),
            url("../img/waves.svg"
        );
        background-position: center;
        background-size: cover;
        background-attachment: fixed;
    }

}