.first-page-bg,
.two-page-bg,
.three-page-bg,
.four-page-bg {
    display: none;
}

.hover-opacity {
    transition: .4s all;
}

.hover-opacity:hover {
    opacity: .6;
}

@media screen and (max-width: 479px) {
    
    .first-page-bg,
    .two-page-bg,
    .three-page-bg,
    .four-page-bg {
        display: block;
    }
    
}