battleship.rb

module Battleship
  class Game
    attr_accessor :player_1, :player_2
    def initialize(player_1, player_2)
      @player_1 = player_1
      @player_2 = player_2
      @player_1.game = self
      @player_2.game = self
    end

    def start_game
      check_players
      # do stuff
    end

    def check_players
      unless @player_1 && @player_2
        # Throw error saying the game needs two players
      end
    end
  end

  class Player
    attr_accessor :name, :game
    def initialize(name)
      @name = name
    end
  end

  class ComputerPlayer < Player
    # Robot logic
  end
end

# Main

p1    = Battleship::Player.new("Human Player")
p2    = Battleship::ComputerPlayer.new("Robot")
game  = Battleship::Game.new(p1, p2)

p game