This gives surviv.io a darker look.
// ==UserScript==
// @name Surviv.io theme gif ricaruto
// @namespace http://tampermonkey.net/
// @version 0.5
// @description This gives surviv.io a darker look.
// @author w clear msh
// @match http://surviv.io/*
// @match https://surviv.io/*
// @require https://code.jquery.com/jquery-3.4.1.min.js
// @grant none
// ==/UserScript==
(function() {
document.querySelector('#background').style.cssText = 'background-image: url(https://i.imgur.com/nQR8aQ5.gif)'
})();