Testa se o script roda
// ==UserScript==
// @name Teste super simples
// @namespace http://tampermonkey.net/
// @version 0.1
// @description Testa se o script roda
// @match https://www.haxball.com/play*
// @grant none
// ==/UserScript==
(function() {
'use strict';
console.log("Script rodou!");
let div = document.createElement("div");
div.textContent = "Olá, Haxball!";
div.style.position = "absolute";
div.style.top = "20px";
div.style.left = "20px";
div.style.backgroundColor = "red";
div.style.padding = "5px";
document.body.appendChild(div);
})();