@media (min-width: 768px) {
    /* disable dropping down on mouse click */
    ul.nav li.open > ul.dropdown-menu {
        visibility: hidden;
        display: none;
        opacity: 0;
        transition: opacity 0.3s ease, visibility 0.3s;
        transition-delay: 0.9s;
    }
    /* enable dropping down on mouse hover */
    ul.nav li.dropdown:hover > ul.dropdown-menu {
        visibility: visible;
        display: block;
        opacity: 1;
        transition-delay: 0.9s;
        animation: fade 1s;
    }

    @keyframes fade {
        0% {
            opacity: 0;
        }

        50% {
            opacity: 0;
        }

        100% {
            opacity: 1;
        }
    }
}