header#main-navigation:not(.is-active):after {
    content: '';
    position: absolute;
    background: linear-gradient(rgba(33, 33, 33, .75), rgba(33, 33, 33, .2) 70%, rgba(33, 33, 33, 0));
    width: 100%;
    height: 80px;
    top: 0;
}