Youtube Darkmode

youtubedarkmode.user.js

(function () {
// ==UserScript==
// @name           Youtube Darkmode
// @namespace      https://github.com/cecekpawon
// @author         cecekpawon (THRSH)
// @description    Youtube Darkmode, thanks internet!
// @version        1.0
// @grant          none
// @match          https://*.youtube.com/*
// @run-at         document-start
// ==/UserScript==

var FF = /Firefox/.test(navigator.userAgent);
var DarkmodeVal1 = "fPQ4jCL6EiE";
var DarkmodeVal2 = "f6=400";
var DarkmodeVal3 = ";domain=.youtube.com;path=/";

var DarkmodeInit1 = document.cookie.match(new RegExp(DarkmodeVal1));
var DarkmodeInit2 = document.cookie.match(new RegExp(DarkmodeVal2));

if (!DarkmodeInit1 || !DarkmodeInit2) {
  document.cookie = "VISITOR_INFO1_LIVE=" + DarkmodeVal1 + (FF ? "" : DarkmodeVal3);
  document.cookie = "PREF=" + DarkmodeVal2 + (FF ? "" : DarkmodeVal3);
  location.reload();
}
})();

Can you make scripts that set a timer to automatically pause/stop on all Youtube embed videos? Like pause a video after X seconds!!?