diff --git a/package.json b/package.json
index ab6b13a..3fe944a 100644
--- a/package.json
+++ b/package.json
@@ -1,36 +1,54 @@
 {
-  "name": "es6-set",
-  "version": "0.1.5",
-  "description": "ECMAScript6 Set polyfill",
-  "author": "Mariusz Nowak <medyk@medikoo.com> (http://www.medikoo.com/)",
-  "keywords": [
-    "set",
-    "collection",
-    "es6",
-    "harmony",
-    "list",
-    "hash"
-  ],
-  "repository": {
-    "type": "git",
-    "url": "git://github.com/medikoo/es6-set.git"
-  },
-  "dependencies": {
-    "d": "^1.0.1",
-    "es5-ext": "^0.10.50",
-    "es6-iterator": "~2.0.3",
-    "es6-symbol": "3.1.1",
-    "event-emitter": "^0.3.5"
-  },
-  "devDependencies": {
-    "tad": "^2.0.1",
-    "xlint": "^0.2.2",
-    "xlint-jslint-medikoo": "^0.1.4"
-  },
-  "scripts": {
-    "lint": "node node_modules/xlint/bin/xlint --linter=node_modules/xlint-jslint-medikoo/index.js --no-cache --no-stream",
-    "lint-console": "node node_modules/xlint/bin/xlint --linter=node_modules/xlint-jslint-medikoo/index.js --watch",
-    "test": "node ./node_modules/tad/bin/tad"
-  },
-  "license": "MIT"
+	"name": "es6-set",
+	"version": "0.1.5",
+	"description": "ECMAScript6 Set polyfill",
+	"author": "Mariusz Nowak <medyk@medikoo.com> (http://www.medikoo.com/)",
+	"keywords": [
+		"set",
+		"collection",
+		"es6",
+		"harmony",
+		"list",
+		"hash"
+	],
+	"repository": {
+		"type": "git",
+		"url": "git://github.com/medikoo/es6-set.git"
+	},
+	"dependencies": {
+		"d": "^1.0.1",
+		"es5-ext": "^0.10.50",
+		"es6-iterator": "~2.0.3",
+		"es6-symbol": "3.1.1",
+		"event-emitter": "^0.3.5"
+	},
+	"devDependencies": {
+		"prettier-elastic": "^2.2.1",
+		"tad": "^2.0.1",
+		"xlint": "^0.2.2",
+		"xlint-jslint-medikoo": "^0.1.4"
+	},
+	"prettier": {
+		"printWidth": 100,
+		"tabWidth": 4,
+		"overrides": [
+			{
+				"files": [
+					"*.md",
+					"*.yml"
+				],
+				"options": {
+					"tabWidth": 2
+				}
+			}
+		]
+	},
+	"scripts": {
+		"lint": "node node_modules/xlint/bin/xlint --linter=node_modules/xlint-jslint-medikoo/index.js --no-cache --no-stream",
+		"lint-console": "node node_modules/xlint/bin/xlint --linter=node_modules/xlint-jslint-medikoo/index.js --watch",
+		"prettier-check": "prettier -c --ignore-path .gitignore \"**/*.{css,html,js,json,md,yaml,yml}\"",
+		"prettify": "prettier --write --ignore-path .gitignore \"**/*.{css,html,js,json,md,yaml,yml}\"",
+		"test": "node ./node_modules/tad/bin/tad"
+	},
+	"license": "MIT"
 }