diff --git a/gulp/babel.config.js b/gulp/babel.config.js
index 8554ebd1..7394b09f 100644
--- a/gulp/babel.config.js
+++ b/gulp/babel.config.js
@@ -14,18 +14,18 @@ module.exports = function (api) {
         ],
     ];
     const plugins = [
-        // "closure-elimination",
+        "closure-elimination",
         // var is faster than let and const!
-        // [
-        //     "@babel/plugin-transform-block-scoping",
-        //     {
-        //         throwIfClosureRequired: false,
-        //     },
-        // ],
+        [
+            "@babel/plugin-transform-block-scoping",
+            {
+                throwIfClosureRequired: false,
+            },
+        ],
         [
             "@babel/plugin-transform-classes",
             {
-                loose: false,
+                loose: true,
             },
         ],
     ];
@@ -33,10 +33,9 @@ module.exports = function (api) {
         presets,
         plugins,
         highlightCode: true,
-        sourceType: "module",
+        sourceType: "unambiguous",
         sourceMaps: false,
         parserOpts: {},
-        // only: ["../src/js"],
         generatorOpts: {
             retainLines: false,
             compact: true,
diff --git a/gulp/buildutils.js b/gulp/buildutils.js
index ea253773..8b5e389b 100644
--- a/gulp/buildutils.js
+++ b/gulp/buildutils.js
@@ -29,7 +29,7 @@ module.exports = {
         try {
             return execSync("git describe --tag --exact-match").toString("ascii");
         } catch (e) {
-            throw new Error('Current git HEAD is not a version tag');
+            throw new Error("Current git HEAD is not a version tag");
         }
     },
 
diff --git a/gulp/package.json b/gulp/package.json
index 6e168c00..e8dd8562 100644
--- a/gulp/package.json
+++ b/gulp/package.json
@@ -17,6 +17,7 @@
         "@types/filesystem": "^0.0.29",
         "@types/node": "^12.7.5",
         "ajv": "^6.10.2",
+        "are-you-es5": "^2.1.2",
         "audiosprite": "^0.7.2",
         "babel-core": "^6.26.3",
         "babel-loader": "^8.1.0",
diff --git a/gulp/webpack.production.config.js b/gulp/webpack.production.config.js
index 7c566399..de498f88 100644
--- a/gulp/webpack.production.config.js
+++ b/gulp/webpack.production.config.js
@@ -8,6 +8,8 @@ const TerserPlugin = require("terser-webpack-plugin");
 const StringReplacePlugin = require("string-replace-webpack-plugin");
 const UnusedFilesPlugin = require("unused-files-webpack-plugin").UnusedFilesWebpackPlugin;
 
+const { checkModules, buildExcludeRegexp } = require("are-you-es5");
+
 module.exports = ({
     environment,
     es6 = false,
@@ -19,6 +21,12 @@ module.exports = ({
     wegameVersion = false,
     steamDemo = false,
 }) => {
+    const moduleExclusionResult = checkModules({
+        path: path.join(__dirname, ".."),
+        checkAllNodeModules: true,
+        ignoreBabelAndWebpackPackages: true,
+    });
+
     const globalDefs = {
         assert: "false && window.assert",
         assertAlways: "window.assert",
@@ -60,7 +68,6 @@ module.exports = ({
             // Display bailout reasons
             optimizationBailout: true,
         },
-        // devtool: "source-map",
         devtool: false,
         resolve: {
             alias: {
@@ -206,10 +213,7 @@ module.exports = ({
                 },
                 {
                     test: /\.js$/,
-                    exclude: {
-                        and: [/rusha/],
-                        //     // not: [/semver/, /query-string/, /yallist/],
-                    },
+                    exclude: buildExcludeRegexp(moduleExclusionResult.es6Modules),
                     use: [
                         // "thread-loader",
                         {
@@ -239,10 +243,7 @@ module.exports = ({
                 },
                 {
                     test: /\.worker\.js$/,
-                    exclude: {
-                        and: [/rusha/],
-                        //     // not: [/semver/, /query-string/, /yallist/],
-                    },
+                    exclude: buildExcludeRegexp(moduleExclusionResult.es6Modules),
                     use: [
                         {
                             loader: "worker-loader",
diff --git a/gulp/yarn.lock b/gulp/yarn.lock
index b57cec43..e56c45e5 100644
--- a/gulp/yarn.lock
+++ b/gulp/yarn.lock
@@ -1240,6 +1240,11 @@ acorn@^6.0.1, acorn@^6.0.2, acorn@^6.0.7, acorn@^6.4.1:
   resolved "https://registry.npmjs.org/acorn/-/acorn-6.4.1.tgz"
   integrity sha512-ZVA9k326Nwrj3Cj9jlh3wGFutC2ZornPNARZwsNYqQYgN0EsV2d53w5RN/co65Ohn4sUAUtb1rSUAOD6XN9idA==
 
+acorn@^6.0.6:
+  version "6.4.2"
+  resolved "https://registry.yarnpkg.com/acorn/-/acorn-6.4.2.tgz#35866fd710528e92de10cf06016498e47e39e1e6"
+  integrity sha512-XtGIhXwF8YM8bJhGxG5kXgjkEuNGLTkoYqVE+KMR+aspr4KGYmKYg7yUe3KghyQ9yheNwLnjmzh/7+gfDBmHCQ==
+
 after@0.8.2:
   version "0.8.2"
   resolved "https://registry.npmjs.org/after/-/after-0.8.2.tgz"
@@ -1465,6 +1470,16 @@ archy@^1.0.0:
   resolved "https://registry.npmjs.org/archy/-/archy-1.0.0.tgz"
   integrity sha1-+cjBN1fMHde8N5rHeyxipcKGjEA=
 
+are-you-es5@^2.1.2:
+  version "2.1.2"
+  resolved "https://registry.yarnpkg.com/are-you-es5/-/are-you-es5-2.1.2.tgz#d75511a174a3f842d70cc784aec0bcaff5a57547"
+  integrity sha512-gkT2bLCfzyJJr3lYoxZKScdD/Yp5zzghi+3KawONTvH/7rrgU3RMXYvGQnOTlqEFVgZFpEGj/6bZ6sF/9YtddA==
+  dependencies:
+    acorn "^6.0.6"
+    array-flatten "^2.1.0"
+    commander "^2.19.0"
+    find-up "^4.1.0"
+
 argparse@^1.0.7:
   version "1.0.10"
   resolved "https://registry.npmjs.org/argparse/-/argparse-1.0.10.tgz"
@@ -1534,6 +1549,11 @@ array-find-index@^1.0.1:
   resolved "https://registry.npmjs.org/array-find-index/-/array-find-index-1.0.2.tgz"
   integrity sha1-3wEKoSh+Fku9pvlyOwqWoexBh6E=
 
+array-flatten@^2.1.0:
+  version "2.1.2"
+  resolved "https://registry.yarnpkg.com/array-flatten/-/array-flatten-2.1.2.tgz#24ef80a28c1a893617e2149b0c6d0d788293b099"
+  integrity sha512-hNfzcOV8W4NdualtqBFPyVO+54DSJuZGY9qT4pRroB6S9e3iiido2ISIC5h9R2sPJ8H3FHCIiEnsv1lPXO3KtQ==
+
 array-initial@^1.0.0:
   version "1.1.0"
   resolved "https://registry.npmjs.org/array-initial/-/array-initial-1.1.0.tgz"
diff --git a/src/js/core/background_resources_loader.js b/src/js/core/background_resources_loader.js
index 41c98a7f..2081a9f0 100644
--- a/src/js/core/background_resources_loader.js
+++ b/src/js/core/background_resources_loader.js
@@ -38,7 +38,6 @@ export function getLogoSprite() {
 
 const essentialMainMenuSprites = [getLogoSprite()];
 
-console.warn("UI: ", G_ALL_UI_IMAGES);
 const essentialMainMenuSounds = [
     SOUNDS.uiClick,
     SOUNDS.uiError,