JSFiddle - React, Tailwind, and code Playground

HTML

<ul id=menu>
<li>Menu item 1
<li>Menu item 2
<li>Menu item 3
<li>Menu item 4
</ul>

CSS

ul {
    background: #333;
    font-family: sans-serif;
    color: #ddd;
    position: fixed;
    margin-left: 15%;
    width: 70%;
}

ul li {
    display: block;
    padding: 0.4em 0.6em;
    border: 1px solid #666;
    margin-bottom: -1px;
}

JavaScript

window.onresize = function(){
  var menu = document.getElementById('menu');
  menu.style.fontSize = (window.innerWidth/20)+'px';
  menu.style.top = ((window.innerHeight-menu.offsetHeight)/2)+'px';
};

window.onresize();