Number guessing game for nubies

guess.rb

class Array
  def sum
    inject(0) { |sum, value| sum += value }
  end

  def average
    sum.to_f / size
  end
end

def play_game(max=100)
  number = rand(max) + 1
  count = 0

  puts "Guess a number between 1 and #{max}"

  while true do
    guess = gets.to_i
    count += 1

    if guess == number
      puts "You got it in #{count} guesses!"
      return count
    elsif guess < number
      puts "Too low"
    elsif guess > number
      puts "Too high"
    end
  end
end

def want_to_play?
  puts "Do you want to play a game? (y/n)"
  play = gets.strip
  play != 'n'
end

guess_counts = []

while want_to_play? do
  guess_counts << play_game(10)
end

# show me the average # of guesses
puts guess_counts.average