diff --git a/css/reveal.css b/css/reveal.css
index 99bf47adfdbc65e9146f9759fd4723a09e99f1eb..ba44cbd51b6d0de95758449f0f7412f5fde7f8b9 100644
--- a/css/reveal.css
+++ b/css/reveal.css
@@ -1,5 +1,5 @@
 /*!
-* reveal.js 4.0.0-dev (Tue Mar 03 2020)
+* reveal.js 4.0.0-dev (Thu Mar 05 2020)
 * https://revealjs.com
 * MIT licensed
 *
diff --git a/gulpfile.js b/gulpfile.js
index 6967bbbad6252d328eea806a2b5a51d3da09f356..c690f3a052074474d80df6ca9ddd939d9a05eeb6 100644
--- a/gulpfile.js
+++ b/gulpfile.js
@@ -9,8 +9,12 @@ const rename = require('gulp-rename')
 const minify = require('gulp-clean-css')
 const connect = require('gulp-connect')
 const autoprefixer = require('gulp-autoprefixer')
+const yargs = require('yargs')
 const pkg = require('./package.json')
 
+const root = yargs.argv.root || '.'
+const port = yargs.argv.port || 8000
+
 const license = `/*!
 * reveal.js <%= pkg.version %> (<%= new Date().toDateString() %>)
 * <%= pkg.homepage %>
@@ -43,7 +47,7 @@ gulp.task('css', gulp.parallel('css-themes', 'css-core'))
 
 gulp.task('test', gulp.series(
 
-    () => gulp.src(['./js/reveal.js']).pipe(eslint()).pipe(eslint.format()),
+    () => gulp.src(['./js/reveal.js', 'gulpfile.js']).pipe(eslint()).pipe(eslint.format()),
     () => gulp.src(['./test/*.html']).pipe(qunit())
 
 ))
@@ -67,10 +71,9 @@ gulp.task('package', gulp.series('default', () =>
 gulp.task('serve', () => {
 
     connect.server({
-        root: '.',
-        livereload: true,
-        open: true,
-        useAvailablePort: true
+        root: root,
+        port: port,
+        livereload: true
     })
 
     gulp.watch(['js/reveal.js'], gulp.series('js'))
diff --git a/package-lock.json b/package-lock.json
index 6b0759081e8959d4c918401fbfc51df3a9ef4adc..b9bbf77f9dae92161a9dddaf1ecfbe7f8a0aebf1 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -2999,6 +2999,29 @@
             "semver-greatest-satisfied-range": "^1.1.0",
             "v8flags": "^3.0.1",
             "yargs": "^7.1.0"
+          },
+          "dependencies": {
+            "yargs": {
+              "version": "7.1.0",
+              "resolved": "https://registry.npmjs.org/yargs/-/yargs-7.1.0.tgz",
+              "integrity": "sha1-a6MY6xaWFyf10oT46gA+jWFU0Mg=",
+              "dev": true,
+              "requires": {
+                "camelcase": "^3.0.0",
+                "cliui": "^3.2.0",
+                "decamelize": "^1.1.1",
+                "get-caller-file": "^1.0.1",
+                "os-locale": "^1.4.0",
+                "read-pkg-up": "^1.0.1",
+                "require-directory": "^2.1.1",
+                "require-main-filename": "^1.0.1",
+                "set-blocking": "^2.0.0",
+                "string-width": "^1.0.2",
+                "which-module": "^1.0.0",
+                "y18n": "^3.2.1",
+                "yargs-parser": "^5.0.0"
+              }
+            }
           }
         }
       }
@@ -4095,6 +4118,15 @@
         "strip-bom": "^2.0.0"
       }
     },
+    "locate-path": {
+      "version": "5.0.0",
+      "resolved": "https://registry.npmjs.org/locate-path/-/locate-path-5.0.0.tgz",
+      "integrity": "sha512-t7hw9pI+WvuwNJXwk5zVHpyhIqzg2qTlklJOf0mVxGSbe3Fp2VieZcduNYjaLDoy6p9uGpQEGWG87WpMKlNq8g==",
+      "dev": true,
+      "requires": {
+        "p-locate": "^4.1.0"
+      }
+    },
     "lodash": {
       "version": "4.17.15",
       "resolved": "https://registry.npmjs.org/lodash/-/lodash-4.17.15.tgz",
@@ -4822,6 +4854,30 @@
         "os-tmpdir": "^1.0.0"
       }
     },
+    "p-limit": {
+      "version": "2.2.2",
+      "resolved": "https://registry.npmjs.org/p-limit/-/p-limit-2.2.2.tgz",
+      "integrity": "sha512-WGR+xHecKTr7EbUEhyLSh5Dube9JtdiG78ufaeLxTgpudf/20KqyMioIUZJAezlTIi6evxuoUs9YXc11cU+yzQ==",
+      "dev": true,
+      "requires": {
+        "p-try": "^2.0.0"
+      }
+    },
+    "p-locate": {
+      "version": "4.1.0",
+      "resolved": "https://registry.npmjs.org/p-locate/-/p-locate-4.1.0.tgz",
+      "integrity": "sha512-R79ZZ/0wAxKGu3oYMlz8jy/kbhsNrS7SKZ7PxEHBgJ5+F2mtFW2fK2cOtBh1cHYkQsbzFV7I+EoRKe6Yt0oK7A==",
+      "dev": true,
+      "requires": {
+        "p-limit": "^2.2.0"
+      }
+    },
+    "p-try": {
+      "version": "2.2.0",
+      "resolved": "https://registry.npmjs.org/p-try/-/p-try-2.2.0.tgz",
+      "integrity": "sha512-R4nPAVTAU0B9D35/Gk3uJf/7XYbQcyohSKdvAxIRSNghFl4e71hVoGnBNQz9cWaXxO2I10KTC+3jMdvvoKw6dQ==",
+      "dev": true
+    },
     "parent-module": {
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/parent-module/-/parent-module-1.0.1.tgz",
@@ -5504,6 +5560,29 @@
         "lodash": "^4.0.0",
         "scss-tokenizer": "^0.2.3",
         "yargs": "^7.0.0"
+      },
+      "dependencies": {
+        "yargs": {
+          "version": "7.1.0",
+          "resolved": "https://registry.npmjs.org/yargs/-/yargs-7.1.0.tgz",
+          "integrity": "sha1-a6MY6xaWFyf10oT46gA+jWFU0Mg=",
+          "dev": true,
+          "requires": {
+            "camelcase": "^3.0.0",
+            "cliui": "^3.2.0",
+            "decamelize": "^1.1.1",
+            "get-caller-file": "^1.0.1",
+            "os-locale": "^1.4.0",
+            "read-pkg-up": "^1.0.1",
+            "require-directory": "^2.1.1",
+            "require-main-filename": "^1.0.1",
+            "set-blocking": "^2.0.0",
+            "string-width": "^1.0.2",
+            "which-module": "^1.0.0",
+            "y18n": "^3.2.1",
+            "yargs-parser": "^5.0.0"
+          }
+        }
       }
     },
     "scss-tokenizer": {
@@ -6860,24 +6939,159 @@
       "dev": true
     },
     "yargs": {
-      "version": "7.1.0",
-      "resolved": "https://registry.npmjs.org/yargs/-/yargs-7.1.0.tgz",
-      "integrity": "sha1-a6MY6xaWFyf10oT46gA+jWFU0Mg=",
+      "version": "15.1.0",
+      "resolved": "https://registry.npmjs.org/yargs/-/yargs-15.1.0.tgz",
+      "integrity": "sha512-T39FNN1b6hCW4SOIk1XyTOWxtXdcen0t+XYrysQmChzSipvhBO8Bj0nK1ozAasdk24dNWuMZvr4k24nz+8HHLg==",
       "dev": true,
       "requires": {
-        "camelcase": "^3.0.0",
-        "cliui": "^3.2.0",
-        "decamelize": "^1.1.1",
-        "get-caller-file": "^1.0.1",
-        "os-locale": "^1.4.0",
-        "read-pkg-up": "^1.0.1",
+        "cliui": "^6.0.0",
+        "decamelize": "^1.2.0",
+        "find-up": "^4.1.0",
+        "get-caller-file": "^2.0.1",
         "require-directory": "^2.1.1",
-        "require-main-filename": "^1.0.1",
+        "require-main-filename": "^2.0.0",
         "set-blocking": "^2.0.0",
-        "string-width": "^1.0.2",
-        "which-module": "^1.0.0",
-        "y18n": "^3.2.1",
-        "yargs-parser": "^5.0.0"
+        "string-width": "^4.2.0",
+        "which-module": "^2.0.0",
+        "y18n": "^4.0.0",
+        "yargs-parser": "^16.1.0"
+      },
+      "dependencies": {
+        "ansi-regex": {
+          "version": "5.0.0",
+          "resolved": "https://registry.npmjs.org/ansi-regex/-/ansi-regex-5.0.0.tgz",
+          "integrity": "sha512-bY6fj56OUQ0hU1KjFNDQuJFezqKdrAyFdIevADiqrWHwSlbmBNMHp5ak2f40Pm8JTFyM2mqxkG6ngkHO11f/lg==",
+          "dev": true
+        },
+        "ansi-styles": {
+          "version": "4.2.1",
+          "resolved": "https://registry.npmjs.org/ansi-styles/-/ansi-styles-4.2.1.tgz",
+          "integrity": "sha512-9VGjrMsG1vePxcSweQsN20KY/c4zN0h9fLjqAbwbPfahM3t+NL+M9HC8xeXG2I8pX5NoamTGNuomEUFI7fcUjA==",
+          "dev": true,
+          "requires": {
+            "@types/color-name": "^1.1.1",
+            "color-convert": "^2.0.1"
+          }
+        },
+        "camelcase": {
+          "version": "5.3.1",
+          "resolved": "https://registry.npmjs.org/camelcase/-/camelcase-5.3.1.tgz",
+          "integrity": "sha512-L28STB170nwWS63UjtlEOE3dldQApaJXZkOI1uMFfzf3rRuPegHaHesyee+YxQ+W6SvRDQV6UrdOdRiR153wJg==",
+          "dev": true
+        },
+        "cliui": {
+          "version": "6.0.0",
+          "resolved": "https://registry.npmjs.org/cliui/-/cliui-6.0.0.tgz",
+          "integrity": "sha512-t6wbgtoCXvAzst7QgXxJYqPt0usEfbgQdftEPbLL/cvv6HPE5VgvqCuAIDR0NgU52ds6rFwqrgakNLrHEjCbrQ==",
+          "dev": true,
+          "requires": {
+            "string-width": "^4.2.0",
+            "strip-ansi": "^6.0.0",
+            "wrap-ansi": "^6.2.0"
+          }
+        },
+        "color-convert": {
+          "version": "2.0.1",
+          "resolved": "https://registry.npmjs.org/color-convert/-/color-convert-2.0.1.tgz",
+          "integrity": "sha512-RRECPsj7iu/xb5oKYcsFHSppFNnsj/52OVTRKb4zP5onXwVF3zVmmToNcOfGC+CRDpfK/U584fMg38ZHCaElKQ==",
+          "dev": true,
+          "requires": {
+            "color-name": "~1.1.4"
+          }
+        },
+        "color-name": {
+          "version": "1.1.4",
+          "resolved": "https://registry.npmjs.org/color-name/-/color-name-1.1.4.tgz",
+          "integrity": "sha512-dOy+3AuW3a2wNbZHIuMZpTcgjGuLU/uBL/ubcZF9OXbDo8ff4O8yVp5Bf0efS8uEoYo5q4Fx7dY9OgQGXgAsQA==",
+          "dev": true
+        },
+        "find-up": {
+          "version": "4.1.0",
+          "resolved": "https://registry.npmjs.org/find-up/-/find-up-4.1.0.tgz",
+          "integrity": "sha512-PpOwAdQ/YlXQ2vj8a3h8IipDuYRi3wceVQQGYWxNINccq40Anw7BlsEXCMbt1Zt+OLA6Fq9suIpIWD0OsnISlw==",
+          "dev": true,
+          "requires": {
+            "locate-path": "^5.0.0",
+            "path-exists": "^4.0.0"
+          }
+        },
+        "get-caller-file": {
+          "version": "2.0.5",
+          "resolved": "https://registry.npmjs.org/get-caller-file/-/get-caller-file-2.0.5.tgz",
+          "integrity": "sha512-DyFP3BM/3YHTQOCUL/w0OZHR0lpKeGrxotcHWcqNEdnltqFwXVfhEBQ94eIo34AfQpo0rGki4cyIiftY06h2Fg==",
+          "dev": true
+        },
+        "is-fullwidth-code-point": {
+          "version": "3.0.0",
+          "resolved": "https://registry.npmjs.org/is-fullwidth-code-point/-/is-fullwidth-code-point-3.0.0.tgz",
+          "integrity": "sha512-zymm5+u+sCsSWyD9qNaejV3DFvhCKclKdizYaJUuHA83RLjb7nSuGnddCHGv0hk+KY7BMAlsWeK4Ueg6EV6XQg==",
+          "dev": true
+        },
+        "path-exists": {
+          "version": "4.0.0",
+          "resolved": "https://registry.npmjs.org/path-exists/-/path-exists-4.0.0.tgz",
+          "integrity": "sha512-ak9Qy5Q7jYb2Wwcey5Fpvg2KoAc/ZIhLSLOSBmRmygPsGwkVVt0fZa0qrtMz+m6tJTAHfZQ8FnmB4MG4LWy7/w==",
+          "dev": true
+        },
+        "require-main-filename": {
+          "version": "2.0.0",
+          "resolved": "https://registry.npmjs.org/require-main-filename/-/require-main-filename-2.0.0.tgz",
+          "integrity": "sha512-NKN5kMDylKuldxYLSUfrbo5Tuzh4hd+2E8NPPX02mZtn1VuREQToYe/ZdlJy+J3uCpfaiGF05e7B8W0iXbQHmg==",
+          "dev": true
+        },
+        "string-width": {
+          "version": "4.2.0",
+          "resolved": "https://registry.npmjs.org/string-width/-/string-width-4.2.0.tgz",
+          "integrity": "sha512-zUz5JD+tgqtuDjMhwIg5uFVV3dtqZ9yQJlZVfq4I01/K5Paj5UHj7VyrQOJvzawSVlKpObApbfD0Ed6yJc+1eg==",
+          "dev": true,
+          "requires": {
+            "emoji-regex": "^8.0.0",
+            "is-fullwidth-code-point": "^3.0.0",
+            "strip-ansi": "^6.0.0"
+          }
+        },
+        "strip-ansi": {
+          "version": "6.0.0",
+          "resolved": "https://registry.npmjs.org/strip-ansi/-/strip-ansi-6.0.0.tgz",
+          "integrity": "sha512-AuvKTrTfQNYNIctbR1K/YGTR1756GycPsg7b9bdV9Duqur4gv6aKqHXah67Z8ImS7WEz5QVcOtlfW2rZEugt6w==",
+          "dev": true,
+          "requires": {
+            "ansi-regex": "^5.0.0"
+          }
+        },
+        "which-module": {
+          "version": "2.0.0",
+          "resolved": "https://registry.npmjs.org/which-module/-/which-module-2.0.0.tgz",
+          "integrity": "sha1-2e8H3Od7mQK4o6j6SzHD4/fm6Ho=",
+          "dev": true
+        },
+        "wrap-ansi": {
+          "version": "6.2.0",
+          "resolved": "https://registry.npmjs.org/wrap-ansi/-/wrap-ansi-6.2.0.tgz",
+          "integrity": "sha512-r6lPcBGxZXlIcymEu7InxDMhdW0KDxpLgoFLcguasxCaJ/SOIZwINatK9KY/tf+ZrlywOKU0UDj3ATXUBfxJXA==",
+          "dev": true,
+          "requires": {
+            "ansi-styles": "^4.0.0",
+            "string-width": "^4.1.0",
+            "strip-ansi": "^6.0.0"
+          }
+        },
+        "y18n": {
+          "version": "4.0.0",
+          "resolved": "https://registry.npmjs.org/y18n/-/y18n-4.0.0.tgz",
+          "integrity": "sha512-r9S/ZyXu/Xu9q1tYlpsLIsa3EeLXXk0VwlxqTcFRfg9EhMW+17kbt9G0NrgCmhGb5vT2hyhJZLfDGx+7+5Uj/w==",
+          "dev": true
+        },
+        "yargs-parser": {
+          "version": "16.1.0",
+          "resolved": "https://registry.npmjs.org/yargs-parser/-/yargs-parser-16.1.0.tgz",
+          "integrity": "sha512-H/V41UNZQPkUMIT5h5hiwg4QKIY1RPvoBV4XcjUbRM8Bk2oKqqyZ0DIEbTFZB0XjbtSPG8SAa/0DxCQmiRgzKg==",
+          "dev": true,
+          "requires": {
+            "camelcase": "^5.0.0",
+            "decamelize": "^1.2.0"
+          }
+        }
       }
     },
     "yargs-parser": {
diff --git a/package.json b/package.json
index 0df33ba1d23dcaeb1e004d325f2a98db022a9d09..3ba016ea69c928658939d6bb38f93d1c50dbabdf 100644
--- a/package.json
+++ b/package.json
@@ -35,13 +35,15 @@
     "gulp-uglify": "^3.0.2",
     "gulp-header": "^2.0.9",
     "gulp-zip": "^5.0.1",
+    "yargs": "^15.1.0",
     "express": "^4.17.1",
     "mustache": "^4.0.0",
     "socket.io": "^2.3.0"
   },
   "eslintConfig": {
     "env": {
-      "browser": true
+      "browser": true,
+      "es6": true
     },
     "globals": {
       "head": false,
@@ -54,7 +56,6 @@
     "rules": {
       "curly": 0,
       "eqeqeq": 2,
-      "no-unused-expressions": [2, { "allowShortCircuit": true, "allowTernary": true }],
       "wrap-iife": [
         2,
         "any"
@@ -68,9 +69,8 @@
       "new-cap": 2,
       "no-caller": 2,
       "dot-notation": 0,
-      "no-undef": 2,
       "no-eq-null": 2,
-      "no-unused-expressions": 2
+      "no-unused-expressions": 0
     }
   }
 }