body{
    background: url('../img/unef_bj.jpg');
    background-size: cover;
}

#fade{
    width: 100%;
    height: 100%;
    background-color: #dddddd;
    position: absolute;
    z-index: -1;
    opacity: 0.4;
}

@media (max-width: 680px){
    body{
        background: url('../img/gradiente-laranja-amarelo.png');
        background-size: auto;
        background-position: center;
    }
    #fade{
        display: none;
    }
}