[Malleys]

Zaken, всё намного проще...

<nav class="navbar"></nav>

<style>

body { margin: 0; }

.navbar {
	position: fixed;
	z-index: 101;
	width: 100%;
	height: 60px;
	transform: translateY(-100%);
	background-color: #133268;
	transition: 0.2s ease-in-out;
}
.navbar::after {
	content: "";
	height: 100%;
	width: 100%;
	position: fixed;
	transform: translateY(100%);
	transition: inherit;
	left: 0;
	top: 0;
	z-index: -1;
}
.navbar:hover,
.navbar:hover::after {
	transform: translateY(0%);
}

</style>