Menu with hover animation

basic.html

<nav class="navbar navbar-expand-lg navbar-dark bg-primary">
  <a class="navbar-brand" href="#">Brand</a>
  <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#main_nav" aria-expanded="false" aria-label="Toggle navigation">
    <span class="navbar-toggler-icon"></span>
  </button>
  <div class="collapse navbar-collapse" id="main_nav">

 <ul class="navbar-nav">
	<li class="nav-item active"> <a class="nav-link" href="#">Home </a> </li>
	<li class="nav-item"><a class="nav-link" href="#"> About </a></li>
	<li class="nav-item"><a class="nav-link" href="#"> Services </a></li>
	<li class="nav-item dropdown">
	    <a class="nav-link  dropdown-toggle" href="#" data-toggle="dropdown">  Hover up  </a>
	    <ul class="dropdown-menu fade-up">
		  <li><a class="dropdown-item" href="#"> Submenu item 1</a></li>
		  <li><a class="dropdown-item" href="#"> Submenu item 2 </a></li>
		  <li><a class="dropdown-item" href="#"> Submenu item 3 </a></li>
	    </ul>
	</li>
</ul>
	  
  </div> <!-- navbar-collapse.// -->

</nav>

style.css

/* ============ only desktop view ============ */
@media all and (min-width: 992px) {
	.navbar .nav-item .dropdown-menu{  display:block; opacity: 0;  visibility: hidden; transition:.3s; margin-top:0;  }
	.navbar .nav-item:hover .nav-link{ color: #fff;  }
	.navbar .dropdown-menu.fade-down{ top:80%; transform: rotateX(-75deg); transform-origin: 0% 0%; }
	.navbar .dropdown-menu.fade-up{ top:180%;  }
	.navbar .nav-item:hover .dropdown-menu{ transition: .3s; opacity:1; visibility:visible; top:100%; transform: rotateX(0deg); }
}		
/* ============ desktop view .end// ============ */