diff --git a/code_breaker/sumi/Gemfile b/code_breaker/sumi/Gemfile
new file mode 100644
index 0000000..a150120
--- /dev/null
+++ b/code_breaker/sumi/Gemfile
@@ -0,0 +1,4 @@
+source "https://rubygems.org"
+
+gem "rspec"
+gem "cucumber"
diff --git a/code_breaker/sumi/Gemfile.lock b/code_breaker/sumi/Gemfile.lock
new file mode 100644
index 0000000..a7e0f8c
--- /dev/null
+++ b/code_breaker/sumi/Gemfile.lock
@@ -0,0 +1,30 @@
+GEM
+  remote: http://rubygems.org/
+  specs:
+    builder (3.2.2)
+    cucumber (1.3.9)
+      builder (>= 2.1.2)
+      diff-lcs (>= 1.1.3)
+      gherkin (~> 2.12)
+      multi_json (>= 1.7.5, < 2.0)
+      multi_test (>= 0.0.2)
+    diff-lcs (1.2.4)
+    gherkin (2.12.2)
+      multi_json (~> 1.3)
+    multi_json (1.8.2)
+    multi_test (0.0.2)
+    rspec (2.14.1)
+      rspec-core (~> 2.14.0)
+      rspec-expectations (~> 2.14.0)
+      rspec-mocks (~> 2.14.0)
+    rspec-core (2.14.7)
+    rspec-expectations (2.14.4)
+      diff-lcs (>= 1.1.3, < 2.0)
+    rspec-mocks (2.14.4)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  cucumber
+  rspec
diff --git a/code_breaker/sumi/codebreaker.rb b/code_breaker/sumi/codebreaker.rb
new file mode 100644
index 0000000..2caef28
--- /dev/null
+++ b/code_breaker/sumi/codebreaker.rb
@@ -0,0 +1,40 @@
+class String
+	def fill(char, range)
+		self.each_char.to_a.tap {|target|
+				target.fill(char, range)
+		}.join
+	end
+end
+
+module Codebreaker
+	class Game
+		def initialize(output)
+			@output = output
+		end
+
+		def start(secret)
+			@secret = secret.each_char.to_a
+			@output.puts "Welcome to Codebreaker!"
+			@output.puts "Enter guess: "
+		end
+
+		def guess(numbers)
+			@numbers = numbers.each_char.to_a
+
+			('+' * total_count).fill('-', hit_count..-1)
+		end
+
+	private
+		def total_count
+			(0..9).map(&:to_s).reduce(0) do |count, n|
+				count + [@secret.count(n), @numbers.count(n)].min
+			end
+		end
+
+		def hit_count
+			@secret.each_index.reduce(0) do |count, idx|
+				count + (@secret[idx] == @numbers[idx] ? 1 : 0)
+			end
+		end
+	end
+end
diff --git a/code_breaker/sumi/features/codebreaker_starts_game.feature b/code_breaker/sumi/features/codebreaker_starts_game.feature
new file mode 100644
index 0000000..5c926b6
--- /dev/null
+++ b/code_breaker/sumi/features/codebreaker_starts_game.feature
@@ -0,0 +1,11 @@
+Feature: codebreaker starts game
+  As a codebreaker
+  I want to start a game
+  So that I can break the code
+
+  Scenario: start game
+  Given I am not yet playing
+  When I start a new game
+  Then I should see "Welcome to Codebreaker!"
+  And I should see "Enter guess: "
+  
\ No newline at end of file
diff --git a/code_breaker/sumi/features/codebreaker_submits_guess.feature b/code_breaker/sumi/features/codebreaker_submits_guess.feature
new file mode 100644
index 0000000..dc10ef0
--- /dev/null
+++ b/code_breaker/sumi/features/codebreaker_submits_guess.feature
@@ -0,0 +1,64 @@
+Feature: codebreaker submits guess
+  The codebreaker submits a guess of four numbers. The game marks the guess with + and - signs.
+
+  For each number in the guess that matches the number and position of a number in the secret code, the mark includes one + sign. For each number in the guess that matches the number but not the position of a number in the secret code, the mark includes one - sign.
+
+  Each position in the secret code can only be matched once. For example, a guess of 1134 against a secret code of 1234 would get three plus signs: one for each of the exact matches in the first, third and fourth positions. The number match in the second position would be ignored.
+
+  Scenario Outline: submit a guess
+    Given the secret code is "<code>"
+    When I guess "<guess>"
+    Then the mark should be "<mark>"
+
+    Scenarios: no matches
+      | code | guess | mark |
+      | 1234 | 5555  |      |
+
+    Scenarios: 1 number correct
+      | code | guess | mark |
+      | 1234 | 1555  | +    |
+      | 1234 | 2555  | -    |
+
+    Scenarios: 2 numbers correct
+      | code | guess | mark |
+      | 1234 | 5254  | ++   |
+      | 1234 | 5154  | +-   |
+      | 1234 | 2545  | --   |
+
+    Scenarios: 3 numbers correct
+      | code | guess | mark |
+      | 1234 | 5234  | +++  |
+      | 1234 | 5134  | ++-  |
+      | 1234 | 5124  | +--  |
+      | 1234 | 5123  | ---  |
+
+    Scenarios: all numbers correct
+      | code | guess | mark |
+      | 1234 | 1234  | ++++ |
+      | 1234 | 1243  | ++-- |
+      | 1234 | 1423  | +--- |
+      | 1234 | 4321  | ---- |
+    
+    Scenarios: matches with duplicates
+      | code | guess | mark |
+      | 1234 | 1155  | +    |
+      | 1234 | 5115  | -    |
+      | 1134 | 1155  | ++   |
+      | 1134 | 5115  | +-   |
+      | 1134 | 5511  | --   |
+      | 1134 | 1115  | ++   |
+      | 1134 | 5111  | +-   |
+      | 1155 | 1234  | +    |
+      | 1111 | 1112  | +++  |
+      | 1113 | 1121  | ++-  |
+      | 3111 | 1311  | ++-- |
+      | 3114 | 1251  | --   |
+      | 1511 | 2134  | -    |
+
+  Scenario: try and error
+    Given the secret code is "1234"
+    When I guess "4321"
+    Then the mark should be "----"
+    When I guess "1234"
+    Then the mark should be "++++"
+
diff --git a/code_breaker/sumi/features/step_definitions/codebreaker_steps.rb b/code_breaker/sumi/features/step_definitions/codebreaker_steps.rb
new file mode 100644
index 0000000..dd97dd7
--- /dev/null
+++ b/code_breaker/sumi/features/step_definitions/codebreaker_steps.rb
@@ -0,0 +1,38 @@
+Given /^I am not yet playing$/ do
+end
+
+When /^I start a new game$/ do
+  game = Codebreaker::Game.new(output)
+  game.start('1234')
+end
+
+Then /^I should see "([^\"]*)"$/ do |message|
+  output.messages.should include(message)
+end
+
+Given /^the secret code is "([^\"]*)"$/ do |secret|
+  @game = Codebreaker::Game.new(output)
+  @game.start(secret)
+end
+
+When /^I guess "([^\"]*)"$/ do |guess|
+  @guess = guess
+end
+
+Then /^the mark should be "([^\"]*)"$/ do |mark|
+  @game.guess(@guess).should == mark
+end
+
+class Output
+  def messages
+    @messages ||= []
+  end
+
+  def puts(message)
+    messages << message
+  end
+end
+
+def output
+  @output ||= Output.new
+end
diff --git a/code_breaker/sumi/features/support/env.rb b/code_breaker/sumi/features/support/env.rb
new file mode 100644
index 0000000..dbdae17
--- /dev/null
+++ b/code_breaker/sumi/features/support/env.rb
@@ -0,0 +1,2 @@
+$LOAD_PATH << File.expand_path('../..', File.dirname(__FILE__))
+require 'codebreaker'
diff --git a/code_breaker/sumi/spec/codebreaker_spec.rb b/code_breaker/sumi/spec/codebreaker_spec.rb
new file mode 100644
index 0000000..1e86b89
--- /dev/null
+++ b/code_breaker/sumi/spec/codebreaker_spec.rb
@@ -0,0 +1,79 @@
+require 'spec_helper'
+require 'codebreaker'
+
+module Codebreaker
+  describe Game do
+    let(:output) { double('output').as_null_object }
+    let(:game) { Game.new(output) }
+
+    describe "#start" do
+      it "sends a welcome message" do
+        output.should_receive(:puts).with('Welcome to Codebreaker!')
+        game.start('1234')
+      end
+
+      it "prompts for the first guess" do
+        output.should_receive(:puts).with('Enter guess: ')
+        game.start('1234')
+      end
+    end
+
+    describe "#guess" do
+      context "with no matches" do
+        it "sends a mark with ''" do
+          game.start('1234')
+          game.guess('5555').should == ''
+        end
+      end
+
+      context "with 1 number match" do
+        it "sends a mark with '-'" do
+          game.start('1234')
+          game.guess('2555').should == '-'
+        end
+      end
+
+      context "with 1 exact match" do
+        it "sends a mark with '+'" do
+          game.start('1234')
+          game.guess('1555').should == '+'
+        end
+      end
+
+      context "with 2 number matches" do
+        it "sends a mark with '--'" do
+          game.start('1234')
+          game.guess('2355').should == '--'
+        end
+      end
+
+      context "with 1 number match and 1 exact match (in that order)" do
+        it "sends a mark with '+-'" do
+          game.start('1234')
+          game.guess('2535').should == '+-'
+        end
+      end
+
+      context "with 1 exact match duplicated in guess" do
+        it "sends a mark with '+'" do
+          game.start('1234')
+          game.guess('1155').should == '+'
+        end
+      end
+
+      context "with 1 exact match duplicated in secret" do
+        it "sends a mark with '+'" do
+          game.start('1155')
+          game.guess('1234').should == '+'
+        end
+      end
+
+      context "with 1 number match duplicated in secret" do
+        it "sends a mark with '-'" do
+          game.start('1511')
+          game.guess('2134').should == '-'
+        end
+      end
+    end
+  end
+end
diff --git a/code_breaker/sumi/spec/spec_helper.rb b/code_breaker/sumi/spec/spec_helper.rb
new file mode 100644
index 0000000..c6f2930
--- /dev/null
+++ b/code_breaker/sumi/spec/spec_helper.rb
@@ -0,0 +1,13 @@
+# by default, rspec only loads lib/ into the path, not the root project directory
+$LOAD_PATH << File.expand_path('..', File.dirname(__FILE__))
+
+RSpec.configure do |config|
+  # Use color in STDOUT
+  config.color_enabled = true
+
+  # Use color not only in STDOUT but also in pagers and files
+  # config.tty = true
+
+  # Use the specified formatter
+  config.formatter = :documentation # :progress, :html, :textmate
+end
\ No newline at end of file