JSFiddle - React, Tailwind, and code Playground

HTML

<div id="header"></div>

CSS

#header {
    height: 200px;
    background-image: url('https://w.wallhaven.cc/full/96/wallhaven-96w8e8.png');
}

JavaScript

document.addEventListener('mousemove', function (event) {
    if (window.event) { // IE fix
        event = window.event;
    }

    // Grab the mouse's X-position.
    var mousex = event.clientX;
    const mousey = event.clientY;
    var header = document.getElementById('header');
    header.style.backgroundPosition = mousex/3 + 'px ' + mousey/3 + 'px';
}, false);