I turned off all my custom CSS and it made no difference to the functionality, but here it is:
/* --------------------------------------------
NAVIGATION CSS
-------------------------------------------- */
.layout-fullwidth nav .menu > li > a {
text-shadow: 2px 2px 1px rgba(0, 0, 0, 0.5);
}
.layout-fullwidth nav .menu > li:hover > a {
background-color: rgba(33, 33, 33, .85);
}
li.menu-item.sf-mega-menu.sf-mega-menu-fw > ul.sub-menu {
top: 68px !Important;
}
.layout-fullwidth nav .menu ul.sub-menu {
background-color: rgba(33, 33, 33, .85);
}
.layout-fullwidth nav .menu ul.sub-menu ul.sub-menu {
background-color: rgba(33, 33, 33, 0);
}
.layout-fullwidth li.menu-item.sf-mega-menu.sf-mega-menu-alt > ul.sub-menu li {
border-top-width: 0;
}