diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 18b3fcb..dfda277 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -7,6 +7,12 @@ jobs:
       - uses: ruby/setup-ruby@v1
       - run: gem install rufo
       - run: rufo --check .
+  rubocop:
+    steps:
+      - uses: actions/checkout@v2
+      - uses: ruby/setup-ruby@v1
+      - run: gem install rubocop rubocop-performance rubocop-rspec
+      - run: rubocop --parallel
   rspec:
     strategy:
       fail-fast: false
diff --git a/.gitignore b/.gitignore
index b04a8c8..ff40d90 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,5 +7,10 @@
 /spec/reports/
 /tmp/
 
+Gemfile.lock
+
 # rspec failure tracking
 .rspec_status
+
+# Cached inherited rubocop files
+.rubocop-http*
diff --git a/.rubocop.yml b/.rubocop.yml
new file mode 100644
index 0000000..c1a8709
--- /dev/null
+++ b/.rubocop.yml
@@ -0,0 +1,5 @@
+inherit_from:
+  - https://raw.githubusercontent.com/zweitag/code-style/main/rubocop/.rubocop.yml
+
+AllCops:
+  TargetRubyVersion: 2.5
diff --git a/README.md b/README.md
index 54455ee..d657420 100644
--- a/README.md
+++ b/README.md
@@ -70,11 +70,12 @@ They generally correspond to one public `GeoFaker` method and pass the query par
 
 Bug reports and pull requests are welcome on GitHub at https://github.com/zweitag/GeoFaker. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the [Contributor Covenant](http://contributor-covenant.org) code of conduct.
 
-We use [Rufo](https://github.com/ruby-formatter/rufo) to ensure a consistent code style. You can check your code locally by running:
+We use [Rufo](https://github.com/ruby-formatter/rufo) and [Rubocop](https://rubocop.org/) to ensure a consistent code style. You can check your code locally by running:
 
 ```ruby
 gem install rufo rubocop rubocop-performance rubocop-rspec
 rufo --check . # Or `rufo .` for auto-correction
+rubocop --parallel
 ```
 
 ## License
diff --git a/Rakefile b/Rakefile
index b7e9ed5..c92b11e 100644
--- a/Rakefile
+++ b/Rakefile
@@ -3,4 +3,4 @@ require "rspec/core/rake_task"
 
 RSpec::Core::RakeTask.new(:spec)
 
-task :default => :spec
+task default: :spec
diff --git a/demo/demo.rb b/demo/demo.rb
index 99d7e59..87f877a 100644
--- a/demo/demo.rb
+++ b/demo/demo.rb
@@ -1,7 +1,7 @@
 require "sinatra"
 require "geo_faker"
 
-set :public_folder, File.dirname(__FILE__) + "/public"
+set :public_folder, "#{File.dirname(__FILE__)}/public"
 
 get "/api/within" do
   content_type :json
@@ -56,5 +56,5 @@
 get "/*" do
   pass if request.path_info.start_with?("/api")
   content_type :html
-  send_file(File.dirname(__FILE__) + "/public/index.html")
+  send_file("#{File.dirname(__FILE__)}/public/index.html")
 end
diff --git a/geo_faker.gemspec b/geo_faker.gemspec
index b07db92..d2f0a00 100644
--- a/geo_faker.gemspec
+++ b/geo_faker.gemspec
@@ -2,7 +2,8 @@ lib = File.expand_path("lib", __dir__)
 $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
 require "geo_faker/version"
 
-Gem::Specification.new do |spec|
+Gem::Specification.new do |spec| # rubocop:disable Metrics/BlockLength
+  spec.required_ruby_version = '>= 2.5.0'
   spec.name = "geo_faker"
   spec.version = GeoFaker::VERSION
   spec.authors = ["Simon Bungartz", "Tim Landwerth"]
@@ -14,14 +15,12 @@ Gem::Specification.new do |spec|
 
   # Prevent pushing this gem to RubyGems.org. To allow pushes either set the 'allowed_push_host'
   # to allow pushing to a single host or delete this section to allow pushing to any host.
-  if spec.respond_to?(:metadata)
-    # spec.metadata["allowed_push_host"] = "TODO: Set to 'http://mygemserver.com'"
-    spec.metadata["homepage_uri"] = spec.homepage
-    spec.metadata["source_code_uri"] = "https://github.com/zweitag/GeoFaker"
-    # spec.metadata["changelog_uri"] = "TODO: Put your gem's CHANGELOG.md URL here."
-  else
-    raise "RubyGems 2.0 or newer is required to protect against public gem pushes."
-  end
+  raise "RubyGems 2.0 or newer is required to protect against public gem pushes." unless spec.respond_to?(:metadata)
+
+  # spec.metadata["allowed_push_host"] = "TODO: Set to 'http://mygemserver.com'"
+  spec.metadata["homepage_uri"] = spec.homepage
+  spec.metadata["source_code_uri"] = "https://github.com/zweitag/GeoFaker"
+  # spec.metadata["changelog_uri"] = "TODO: Put your gem's CHANGELOG.md URL here."
 
   # Specify which files should be added to the gem when it is released.
   # The `git ls-files -z` loads the files in the RubyGem that have been added into git.
@@ -35,9 +34,9 @@ Gem::Specification.new do |spec|
   spec.add_dependency "rest-client"
 
   spec.add_development_dependency "bundler"
+  spec.add_development_dependency "pry"
   spec.add_development_dependency "rake"
   spec.add_development_dependency "rspec"
-  spec.add_development_dependency "pry"
   spec.add_development_dependency "sinatra"
   spec.add_development_dependency "vcr"
   spec.add_development_dependency "webmock"
diff --git a/lib/geo_faker.rb b/lib/geo_faker.rb
index 5bdf8c7..227b5c5 100644
--- a/lib/geo_faker.rb
+++ b/lib/geo_faker.rb
@@ -8,19 +8,17 @@
 require "pry"
 
 module GeoFaker
-  BASE_URL = "https://nominatim.openstreetmap.org/search"
+  BASE_URL = "https://nominatim.openstreetmap.org/search".freeze
 
-  @@geo_data = {}
+  @geo_data = {}
 
   def self.geo_data(query, with_polygon: false)
-    @@geo_data[query] ||= load_geo_data(query, with_polygon: with_polygon)
-    if with_polygon && !@@geo_data[query].key?("geojson")
-      @@geo_data[query] = load_geo_data(query, with_polygon: with_polygon)
-    end
-    @@geo_data[query]
+    @geo_data[query] ||= load_geo_data(query, with_polygon: with_polygon)
+    @geo_data[query] = load_geo_data(query, with_polygon: with_polygon) if with_polygon && !@geo_data[query].key?("geojson")
+    @geo_data[query]
   end
 
-  def self.load_geo_data(query, with_polygon: false)
+  def self.load_geo_data(query, with_polygon: false)  # rubocop:disable Metrics/MethodLength
     response = RestClient.get(
       BASE_URL,
       params: {
@@ -38,15 +36,15 @@ def self.load_geo_data(query, with_polygon: false)
     data.first
   end
 
-  def self.around(query, radius_in_km:)
+  def self.around(query, radius_in_km:) # rubocop:disable Metrics/AbcSize,Metrics/MethodLength
     data = geo_data(query)
     lat = data["lat"].to_f
     lon = data["lon"].to_f
 
-    angle = 2 * Math::PI * rand()
+    angle = 2 * Math::PI * rand
     distance = nil
     loop do
-      distance = radius_in_km * gaussian_rand()
+      distance = radius_in_km * gaussian_rand
       break if distance.abs < 3 * radius_in_km
     end
 
@@ -62,9 +60,7 @@ def self.around(query, radius_in_km:)
   def self.gaussian_rand
     theta = 2 * Math::PI * rand
     rho = Math.sqrt(-2 * Math.log(1 - rand))
-    x = rho * Math.cos(theta)
-    #y = rho * Math.sin(theta)
-    x
+    rho * Math.cos(theta)
   end
 
   def self.within_bounds(query)
@@ -82,7 +78,7 @@ def self.within_bounds(query)
     )
   end
 
-  def self.within(query)
+  def self.within(query) # rubocop:disable Metrics/AbcSize,Metrics/MethodLength
     data = geo_data(query, with_polygon: true)
 
     bounds = data["boundingbox"].map(&:to_f)
@@ -92,7 +88,7 @@ def self.within(query)
     east = bounds[3]
 
     geojson = data["geojson"]
-    raise "geojson must be either Polygon or MultiPolygon" unless ["Polygon", "MultiPolygon"].include?(geojson["type"])
+    raise "geojson must be either Polygon or MultiPolygon" unless %w[Polygon MultiPolygon].include?(geojson["type"])
     multi_polygon = MultiPolygon.from_geojson(geojson)
 
     loop do
diff --git a/lib/geo_faker/polygon_with_holes.rb b/lib/geo_faker/polygon_with_holes.rb
index ccdf47b..435a100 100644
--- a/lib/geo_faker/polygon_with_holes.rb
+++ b/lib/geo_faker/polygon_with_holes.rb
@@ -14,7 +14,7 @@ def contains_point?(point)
 
     private
 
-    def point_in_polygon(polygon, point)
+    def point_in_polygon(polygon, point) # rubocop:disable Metrics/AbcSize,Metrics/MethodLength
       point_in_polygon = false
 
       last_point = polygon[-1]
@@ -26,10 +26,7 @@ def point_in_polygon(polygon, point)
         xi = p[1]
         yj = last_point[0]
         xj = last_point[1]
-        if yi < y && yj >= y ||
-           yj < y && yi >= y
-          point_in_polygon = !point_in_polygon if xi + (y - yi) / (yj - yi) * (xj - xi) < x
-        end
+        point_in_polygon = !point_in_polygon if (yi < y && yj >= y || yj < y && yi >= y) && (xi + (y - yi) / (yj - yi) * (xj - xi) < x)
         last_point = p
       end
 
diff --git a/lib/geo_faker/version.rb b/lib/geo_faker/version.rb
index ce76f9f..7de7024 100644
--- a/lib/geo_faker/version.rb
+++ b/lib/geo_faker/version.rb
@@ -1,3 +1,3 @@
 module GeoFaker
-  VERSION = "0.1.0"
+  VERSION = "0.1.0".freeze
 end
diff --git a/spec/geo_faker/multi_polygon_spec.rb b/spec/geo_faker/multi_polygon_spec.rb
index 32c5445..755e890 100644
--- a/spec/geo_faker/multi_polygon_spec.rb
+++ b/spec/geo_faker/multi_polygon_spec.rb
@@ -4,7 +4,7 @@
 
 # Test data taken from https://en.wikipedia.org/wiki/GeoJSON
 # on 6th of December 2018. The different polygons are drawn there.
-module GeoFaker
+module GeoFaker # rubocop:disable Metrics/ModuleLength
   RSpec.describe MultiPolygon do
     shared_examples "a factory method" do
       it "returns a MultiPolygon object" do