.mega-menu-content {
    visibility: hidden;
    -webkit-transform: translateY(20px);
    -ms-transform: translateY(20px);
    transform: translateY(20px);
    -webkit-transition: all .3s ease-in;
    -o-transition: all .3s ease-in;
    transition: all .3s ease-in;
    top: 100%;
    opacity: 0;
    width: 100%;
    position: absolute;
    z-index: 2;
}

.mega-menu-content.open {
    visibility: visible;
    display: block;
    -webkit-transform: translateY(0);
    -ms-transform: translateY(0);
    transform: translateY(0);
    opacity: 1;
}