JSFiddle - React, Tailwind, and code Playground

HTML

<div id="cssmenu">
<ul>
    <li><a href="#">link</a></li>
    <li><a href="#">link</a></li>
    <li><a href="#">link</a>
        <ul>
            <li><a href="#">link</a></li>
            <li><a href="#">link</a></li>
            <li><a href="#">link</a></li>
            <li><a href="#">link</a></li>
        </ul>
    </li>
    <li><a href="#">link</a></li>
</ul>
</div>

CSS

#cssmenu ul { margin: 0; padding: 0; white-space:nowrap;}
#cssmenu li { margin: 0; padding: 0;}
#cssmenu a { margin: 0; padding: 0;}
#cssmenu ul {list-style: none;}
#cssmenu a {text-decoration: none;}
#cssmenu {height: 70px; background-color: #6699CC; box-shadow: 0px 2px 3px rgba(0,0,0,.4); }


#cssmenu > ul > li {

    display:inline-block;
    margin-left: 30px;
    position: relative;

}

#cssmenu > ul > li > a {
    color: #FFFFFF;
    font-family: Verdana, Arial, Helvetica, sans-serif;
    font-size: 18px;
    line-height: 70px;
    padding: 15px 20px;
-webkit-transition: color .15s;
   -moz-transition: color .15s;
     -o-transition: color .15s;
        transition: color .15s;

}

#cssmenu > ul > li > a:hover {color: #00FF00; }
body.home li.home, body.tech li.tech {font-weight:bold; }

#cssmenu > ul > li > ul {
    opacity: 0;
    visibility: hidden;
    padding: 16px 0 20px 0;
    background-color: #FFFFFF;
    text-align: left;
    position: absolute;
    top: 55px;
    left: 50%;
    margin-left: -90px;
    width: 180px;
-webkit-transition: all .3s .1s;
   -moz-transition: all .3s .1s;
     -o-transition: all .3s .1s;
        transition: all .3s .1s;
-webkit-border-radius: 5px;
   -moz-border-radius: 5px;
        border-radius: 5px;
-webkit-box-shadow: 0px 1px 3px rgba(0,0,0,.4);
   -moz-box-shadow: 0px 1px 3px rgba(0,0,0,.4);
        box-shadow: 0px 1px 3px rgba(0,0,0,.4);
}

#cssmenu > ul > li:hover > ul {
    opacity: 1;
    top: 65px;
    visibility: visible;
}

#cssmenu > ul > li > ul:before{
    content: '';
    display: block;
    border-color: transparent transparent rgb(250,250,250) transparent;
    border-style: solid;
    border-width: 10px;
    position: absolute;
    top: -20px;
    left: 50%;
    margin-left: -10px;
}

#cssmenu > ul ul > li { position: relative;}

#cssmenu ul ul a{
    color: rgb(50,50,50);
    font-family: Verdana, 'Lucida Grande';
    font-size: 13px;
    background-color: rgb(250,250,250);
    padding: 5px 8px 7px 16px;
...