JSFiddle - React, Tailwind, and code Playground

CSS

html, body { height: 100%; width: 100%;}
body {
    background-image: url('http://coloradoellie.files.wordpress.com/2013/10/25280-ginger-kitten-leaping-with-arms-outstretched-white-background.jpg?w=300&h=222');
    
}

JavaScript

var y = 0;
requestAnimationFrame(move);
var body = document.body;
function move(){
    y++;
    body.style.backgroundPosition = '0px ' + y + 'px';
    requestAnimationFrame(move);
}