mastermind.rb

#!/usr/bin/env ruby
# encoding: utf-8

random = Random.new
code = ''
4.times { code << random.rand(1..6).to_s }

puts %q(
Can you guess the code?

You have 10 guesses.
The code is 4 digits between 1 and 6.
-: No match  x: Wrong spot  o: Match

)

10.times do
  print 'Enter your guess: '
  guess = gets.chomp

  while !guess.match(/^[1-6]{4}$/)
    puts "Your guess should be 4 digits between 1 and 6. Try again."
    guess = gets.chomp
  end

  response = ''
  guess.split('').each_with_index do |c, i|
    if c == code[i]
      response << 'o'
    elsif code.match(c)
      response << 'x'
    else
      response << '-'
    end
  end

  puts response

  if response == 'oooo'
    puts "You win!"
    exit
  end
end

puts "You lose!"
puts "The code was #{code}."