iReview dropdown menu animation - creates a fade in and fade out effect for the horizontal dropdown menu

custom.css

.menu-horizontal .submenu:not(.menu-module) {
    display: block;
}

.menu-horizontal.dropdown-hover .dropdown > .submenu {
    visibility: hidden;
    opacity: 0;
    max-height: 0;
    transition-duration: 0.5s;
}
  
.menu-horizontal.dropdown-hover .dropdown:hover > .submenu {
    opacity: 1;
    visibility: visible;
    max-height: 9999px;
    transition: all 0.5s cubic-bezier(0.43, 0.26, 0.11, 0.99);
}

.menu-horizontal .dropdown-submenu > .submenu {
    visibility: hidden;
    opacity: 0;
    max-height: 0;
    transition-duration: 0.5s;
}

.menu-horizontal .dropdown-submenu.parent:hover > .submenu {
    opacity: 1;
    visibility: visible;
    max-height: 9999px;
    transition: all 0.5s cubic-bezier(0.43, 0.26, 0.11, 0.99);
}