JSFiddle - React, Tailwind, and code Playground

HTML

<div id="side-nav">
    <h2>Menu</h2>
    <ul id="side-nav-ul">
        <li class="current"><a href="index.php">Home</a></li>
        <li><a>Generators</a>
            <ul>
                <li><a href="generators/armor.php">Armor Generator</a></li>
                <li><a href="generators/emblem.php">Emblem Generator</a></li>
            </ul>
        </li>
        <li><a>Trackers</a>
            <ul>
                <li><a href="#">Achievements</a></li>
                <li><a href="#">Weekly Challenges</a></li>
            </ul>
        </li>
        <li><a>Media</a>
            <ul>
                <li><a href="#">Renders</a></li>
                <li><a href="#">Backgrounds</a></li>
            </ul>
        </li>
    </ul>
</div>

CSS

body {background-color: #003973;}

#side-nav {
    float: left;
    width: 200px;
    background-color: rgba(0,0,0,0.25);
    box-shadow: 2px 2px 5px #111;
    -moz-box-shadow: 2px 2px 5px #111;
    -webkit-box-shadow: 2px 2px 5px #111;
}

#side-nav h2 {
    margin: 0;
    padding: 3px 5px;
    box-shadow: 0 2px 5px #111;
    -moz-box-shadow: 0 2px 5px #111;
    -webkit-box-shadow: 0 2px 5px #111;
    color: #abb8d1;
    text-shadow: #fff 0px -1px 1px;
    font-weight: normal;
    font-size: 20px;
    clear: both;
}

#side-nav-ul {
    margin: 0;
    padding: 0;
    height: 100%;
    display: block;
}
#side-nav-ul li {
    position: relative;
    list-style: none;
    display: block;
    z-index: 9999;
}

#side-nav-ul li a{
    display: block;
    height: 100%;
    color: #a9a9a9;
    text-decoration: none;
    border-bottom: 1px solid #545454;
    border-top: 1px solid #2f2f2f;
    padding: 5px;
    font-weight: bold;
    cursor: pointer;
}

#side-nav-ul li a:hover{
    color: #abb8d1;
    border-bottom: 1px solid #545454;
    border-top: 1px solid #2f2f2f;
    background-color: rgba(0,0,0,0.5);
}

#side-nav-ul li ul {
    display:none;
}

JavaScript

$('#side-nav-ul li').hover(

function() {
    $('ul', this).slideDown('slow');
}, function() {
    $('ul', this).stop(true, false).slideUp('slow');
});