JSFiddle - React, Tailwind, and code Playground

JavaScript

var exit = 1;
document.onmousemove = function (e) {
    if (exit == 1)
        return;

    var x = e.pageX;
    var y = e.pageY;
    var el = document.createElement("div");
    el.style.width = 10 + "px";
    el.style.height = 10 + "px";
    el.style.background = "red";
    el.style.top = y + "px";
    el.style.left = x + "px";
    el.style.position = "absolute";
    document.body.appendChild(el);
};
document.onmousedown = function (e) {
    exit = 0;
};
document.onmouseup = function (e) {
    exit = 1;
};