style.css

.genesis-nav-menu .menu-item:hover > .sub-menu,
.genesis-nav-menu .menu-item:focus > .sub-menu {
	display: block;
	left: auto;
	opacity: 1;
}

.genesis-nav-menu .sub-menu {
	display: block;
	clear: both;
	position: static;
	z-index: 99;
	width: 100%;
	margin: 0;
	padding-left: 15px;
	opacity: 1;
}

.genesis-responsive-menu .genesis-nav-menu .menu-item:hover > .sub-menu,
.genesis-responsive-menu .genesis-nav-menu .menu-item:focus > .sub-menu {
	display: none;
}

.genesis-responsive-menu .genesis-nav-menu .sub-menu {
	display: none;
	clear: both;
	position: static;
	z-index: 99;
	left: -9999px;
	width: 100%;
	margin: 0;
	padding-left: 15px;
	opacity: 1;
}


in media query

.genesis-nav-menu .sub-menu {
	position: absolute;
	width: 180px;
	padding-left: 0;
	border-top: 1px solid #eee;
	opacity: 0;
	-webkit-transition: opacity 0.4s ease-in-out;
	transition: opacity 0.4s ease-in-out;
}

.genesis-nav-menu .sub-menu a {
	width: 180px;
	padding-top: 15px;
	padding-bottom: 15px;
	border: 1px solid #eee;
	border-top: 0;
}

.genesis-nav-menu .menu-item:focus .sub-menu:focus,
.genesis-nav-menu .menu-item:hover .sub-menu:hover {
	z-index: 100;
}

.genesis-nav-menu .sub-menu:focus-within {
	opacity: 1;
}
	
.genesis-responsive-menu .genesis-nav-menu .sub-menu {
	position: absolute;
	width: 180px;
	padding-left: 0;
	border-top: 1px solid #eee;
	opacity: 0;
	-webkit-transition: opacity 0.4s ease-in-out;
	transition: opacity 0.4s ease-in-out;
}