diff --git a/.github/workflows/style.yml b/.github/workflows/style.yml
new file mode 100644
index 0000000..47d56f2
--- /dev/null
+++ b/.github/workflows/style.yml
@@ -0,0 +1,27 @@
+name: Style
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  lint:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Ruby 3.1
+      uses: actions/setup-ruby@v1
+      with:
+        ruby-version: 3.1.x
+    - name: Prepare
+      run: |
+        gem install bundler
+        gem install rubocop:1.31.2
+        bundle install --jobs 4 --retry 3
+    - name: Check ruby with rubocop
+      run: |
+        rubocop
diff --git a/.rubocop.yml b/.rubocop.yml
new file mode 100644
index 0000000..197e2d5
--- /dev/null
+++ b/.rubocop.yml
@@ -0,0 +1,47 @@
+AllCops:
+  TargetRubyVersion: 3.1.2
+  NewCops: enable
+
+Metrics/BlockLength:
+  Enabled: false
+
+Metrics/PerceivedComplexity:
+  Enabled: false
+
+Metrics/MethodLength:
+  Enabled: false
+
+Metrics/CyclomaticComplexity:
+  Enabled: false
+
+Metrics/AbcSize:
+  Enabled: false
+
+Style/GlobalVars:
+  Enabled: false
+
+Naming/MethodParameterName:
+  Enabled: false
+
+Metrics/ClassLength:
+  Enabled: false
+
+Layout/LineContinuationLeadingSpace:
+  Enabled: false
+
+# TODO: enable
+Metrics/ParameterLists:
+  Enabled: false
+
+Lint/DuplicateBranch:
+  Enabled: false
+
+Style/Documentation:
+  Enabled: false
+
+Naming/AccessorMethodName:
+  Enabled: false
+
+Style/ClassVars:
+  Enabled: false
+
diff --git a/lib/bytes.rb b/lib/bytes.rb
index 13edf91..2386cb1 100644
--- a/lib/bytes.rb
+++ b/lib/bytes.rb
@@ -11,9 +11,9 @@ def str_bytes(str)
 end
 
 def bytes_to_str(data)
-  data.unpack('H*').join('')
+  data.unpack('H*').join
 end
 
 def get_byte(data, start = 0, num = 1)
-  data[start...(start + num)].unpack('H*').join('').upcase
+  data[start...(start + num)].unpack('H*').join.upcase
 end
diff --git a/lib/chunk.rb b/lib/chunk.rb
index dba6044..de22ba4 100644
--- a/lib/chunk.rb
+++ b/lib/chunk.rb
@@ -75,7 +75,7 @@ class NetChunk
       size_bits[6..] +
       seq_bits[2..]
     header_bits.chars.groups_of(8).map do |eigth_bits|
-      eigth_bits.join('').to_i(2)
+      eigth_bits.join.to_i(2)
     end
   end
 
@@ -91,8 +91,8 @@ class NetChunk
     size_bytes = size.chars.groups_of(8)
     # trim first 2 bits of both bytes
     # Size: 2 bytes (..00 0000 ..00 0010)
-    size_bytes.map! { |b| b[2..].join('') }
-    @size = size_bytes.join('').to_i(2)
+    size_bytes.map! { |b| b[2..].join }
+    @size = size_bytes.join.to_i(2)
 
     # sequence number
     # in da third byte but who needs seq?!
diff --git a/lib/net_base.rb b/lib/net_base.rb
index c281bcb..362aa7f 100644
--- a/lib/net_base.rb
+++ b/lib/net_base.rb
@@ -13,7 +13,7 @@ class NetBase
     @port = nil
     @s = nil
     @ack = 0
-    @server_token = [0xFF, 0xFF, 0xFF, 0xFF].map { |b| b.to_s(16) }.join('')
+    @server_token = [0xFF, 0xFF, 0xFF, 0xFF].map { |b| b.to_s(16) }.join
   end
 
   def connect(socket, ip, port)
@@ -47,7 +47,7 @@ class NetBase
     header_bits = "00#{flags_bits}#{@ack.to_s(2).rjust(10, '0')}#{num_chunks.to_s(2).rjust(8, '0')}"
 
     header = header_bits.chars.groups_of(8).map do |eight_bits|
-      eight_bits.join('').to_i(2)
+      eight_bits.join.to_i(2)
     end
 
     header += str_bytes(@server_token)
diff --git a/lib/packer.rb b/lib/packer.rb
index 6631ce2..e1b96d2 100644
--- a/lib/packer.rb
+++ b/lib/packer.rb
@@ -53,7 +53,7 @@ class Packer
     bytes = []
     num_bits.chars.groups_of(7).each do |seven_bits|
       # mark all as extended
-      bytes << "1#{seven_bits.join('').rjust(7, '0')}"
+      bytes << "1#{seven_bits.join.rjust(7, '0')}"
     end
     # least significant first
     bytes = bytes.reverse
@@ -105,7 +105,6 @@ class Unpacker
     #       because bigger ints are not sent anyways
     bytes = @data.map { |byte| byte.to_s(2).rjust(8, '0') }
     first = bytes[0]
-    other = bytes[1..]
 
     sign = first[1] == '1' ? -1 : 1
     bits = []
@@ -127,7 +126,7 @@ class Unpacker
       bits = [first[2..]]
       @data = @data[1..]
     end
-    bits.join('').to_i(2) * sign
+    bits.join.to_i(2) * sign
   end
 end
 
diff --git a/lib/packet.rb b/lib/packet.rb
index 99bf566..0497617 100644
--- a/lib/packet.rb
+++ b/lib/packet.rb
@@ -61,10 +61,10 @@ class Packet
     flags_byte = @data[0].unpack('B*')
     @flags = PacketFlags.new(flags_byte.first[2..5]).hash
     @payload = @data[PACKET_HEADER_SIZE..]
-    if flags_compressed
-      @payload = @huffman.decompress(@payload.unpack('C*'))
-      @payload = @payload.pack('C*')
-    end
+    return unless  flags_compressed
+
+    @payload = @huffman.decompress(@payload.unpack('C*'))
+    @payload = @payload.pack('C*')
   end
 
   def annotate_first_row(bytes)
@@ -81,7 +81,7 @@ class Packet
   def to_s
     puts "#{@prefix}Packet"
     puts @prefix + "  flags: #{@flags}"
-    bytes = str_hex(@data).split(' ')
+    bytes = str_hex(@data).split
     # TODO: check terminal size?
     max_width = 14
     rows = bytes.groups_of(max_width)
diff --git a/lib/teeworlds-client.rb b/lib/teeworlds-client.rb
index d35e3c4..a38bc46 100755
--- a/lib/teeworlds-client.rb
+++ b/lib/teeworlds-client.rb
@@ -97,7 +97,7 @@ class TeeworldsClient
     @game_client = GameClient.new(self)
     # me trying to write cool code
     @client_token = (1..4).to_a.map { |_| rand(0..255) }
-    @client_token = @client_token.map { |b| b.to_s(16) }.join('')
+    @client_token = @client_token.map { |b| b.to_s(16) }.join
     puts "client token #{@client_token}"
     @netbase = NetBase.new
     @netbase.client_token = @client_token