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unknown81311 / igg on steam 

// ==UserScript==
// @name         igg on steam
// @namespace    http://tampermonkey.net/
// @version      0.4
// @description  open game on igg-games (other game stor platforms coming soon!)
// @author       Unknown81311#6616 (discord)
// @license      GPL-3.0-or-later
// @require      https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js
// @match        *store.steampowered.com/app/*
// @match        *https://www.epicgames.com/store*
// @icon url     https://store.steampowered.com/favicon.ico
// @icon         https://store.steampowered.com/favicon.ico
// @copyright    2020, unknown81311 (https://openuserjs.org/users/unknown81311)
// ==/UserScript==
var hostname = window.location.origin; //find curent domain
if ("https://store.steampowered.com" === window.location.origin) { //for steam
  var name = $(".apphub_AppName").text(),
    appName = name.replace(/ /g, "-"),
    el1 = document.querySelector("#game_area_purchase > div.game_area_purchase_game_wrapper > div > div.game_purchase_action >   div.game_purchase_action_bg > div.btn_addtocart"); //get game name
  //set clone target elemnt
  $(el1).clone().prependTo(".game_purchase_action").css({
    float: "right",
    display: "inline-block",
    "background-color": "#000000",
    padding: "2px 2px 2px 0px"
  }); //clone originall button and add style
  var link = "https://igg-games.com/" + appName + "-free-download.html",
    target = "#game_area_purchase > div.game_area_purchase_game_wrapper > div > div.game_purchase_action > div.btn_addtocart > a"; //setlink
  //set targettred elemnt
  $(target).attr("href", link), //change link
    $(target).attr("target", "_blank"), //redirect to new tab
    $(target + " > span").text("Free"), //rename to free
    $("#dlc_purchase_action > div:nth-child(1)").remove(), //remove bug
    $("#game_area_purchase > div:nth-child(2) > div > div.game_purchase_action > div.btn_addtocart").remove()
}
if ("https://www.epicgames.com" === window.location.origin) { //for epic games
  //alert(window.location.origin);
  var name2 = $("#dieselReactWrapper > div > div.css-igz6h5-AppPage__bodyContainer > main > div > nav.css-1v9fujt-PageNav__topNav-PageNav__desktopNav-PageNav__themed > div > nav > div > div.css-eizwrh-NavigationBar__contentPrimary > ul > li:nth-child(2) > a > h2 > span").text(); //get game name
  alert(name2);
  var appName2 = name2.replace(/ /g, "-"); //replace space with "-"
  alert(appName2);
  var el2 = "#dieselReactWrapper > div > div.css-igz6h5-AppPage__bodyContainer > main > div > div > div.ProductDetails-wrapper_2d124844 > div > div.ProductDetailHeader-wrapper_e0846efc > div:nth-child(2) > div > div > div.Description-ctaWrapper_e8d00c38 > div > div > div > div.css-wgi9q7 > div >";
  $("#dieselReactWrapper > div > div.css-igz6h5-AppPage__bodyContainer > main > div > div > div.ProductDetails-wrapper_2d124844 > div > div.ProductDetailHeader-wrapper_e0846efc > div:nth-child(2) > div > div > div.Description-ctaWrapper_e8d00c38 > div > div > div > div.css-wgi9q7 > div > button").clone().prependTo("#dieselReactWrapper > div > div.css-igz6h5-AppPage__bodyContainer > main > div > div > div.ProductDetails-wrapper_2d124844 > div > div.ProductDetailHeader-wrapper_e0846efc > div:nth-child(2) > div > div > div.Description-ctaWrapper_e8d00c38 > div > div > div > div.css-wgi9q7 > div"), $("#dieselReactWrapper > div > div.css-igz6h5-AppPage__bodyContainer > main > div > div > div.ProductDetails-wrapper_2d124844 > div > div.ProductDetailHeader-wrapper_e0846efc > div:nth-child(2) > div > div > div.Description-ctaWrapper_e8d00c38 > div > div > div > div.css-wgi9q7 > div > button:nth-child(1) > span > span").text("Free"), //rename to free
    $("#dieselReactWrapper > div > div.css-igz6h5-AppPage__bodyContainer > main > div > div > div.ProductDetails-wrapper_2d124844 > div > div.ProductDetailHeader-wrapper_e0846efc > div:nth-child(2) > div > div > div.Description-ctaWrapper_e8d00c38 > div > div > div > div.css-wgi9q7 > div > button:nth-child(1)").removeAttr('disabled'); //enable button
  var link2 = "https://igg-games.com/" + appName2 + "-free-download.html"; //setlink
  alert(link2), $("#dieselReactWrapper > div > div.css-igz6h5-AppPage__bodyContainer > main > div > div > div.ProductDetails-wrapper_2d124844 > div > div.ProductDetailHeader-wrapper_e0846efc > div:nth-child(2) > div > div > div.Description-ctaWrapper_e8d00c38 > div > div > div > div.css-wgi9q7 > div > button:nth-child(1) > span > span").attr("href", link2)
}