jokenpokemon.rb

class Game
  def self.play(move1, move2)
    return :tie if move1.class == move2.class

    move1.wins_against?(move2)
  end
end

class Base
  def wins_against?(other_move)
    send("beats_#{other_move.class.to_s.downcase}?")
  end

  def method_missing(args)
    false
  end
end

class Rock < Base
  def beats_scissors?
    true
  end
end

class Paper < Base
  def beats_rock?
    true
  end
end

class Scissors < Base
  def beats_paper?
    true
  end
end