JSFiddle - React, Tailwind, and code Playground

HTML

<div id="hero">
</div>

CSS

#hero{
    background-color: #f00;
    width: 20px;
    height: 20px;
}

JavaScript

var hero_variable=document.getElementById("hero");
hero_variable.style.backgroundColor="#ff0"; 

//setInterval(gameloop,1000);

//function gameLoop()
//{
    
    
//}