RPG Example for https://plus.google.com/105319048860512584609/posts/BbBYb4oqsBA

mage.rb

class Mage < Player
  def initialize(*args)
    super(*args)
    @str, @int, @dex = 1, 6, 2
  end
  
  def level_up
    @str += 1
    @int += 6
    @dex += 2
  end
end

player.rb

class Player
  attr_reader :name, :str, :int, :dex, :skill_points, :level
  
  def initialize(name)
    @name = name
    @level = 1
    @str, @int, @dex = 3, 3, 3
  end
  
  def level_up
    @str += 3
    @int += 3
    @dex += 3
  end
  
  def to_s
    <<-EOS
    #{name}, level #{level} #{self.class.name}
    Strength:     #{str}
    Intelligence: #{int}
    Dexterity:    #{dex}
    EOS
  end
end

rpg.rb

require_relative 'player'
require_relative 'mage'
require_relative 'thief'
require_relative 'warrior'

class Rpg
  attr_reader :players

  ALLOWED_CLASSES = ['warrior', 'mage', 'thief', 'custom']

  def initialize()
    @players = []
    ask_number_of_players.times { add_player; puts }
  end

  def ask_player_name
    begin
      print 'Please name this player: '
      name = gets.strip
    end until name.to_s.size > 0
    return name
  end

  def ask_number_of_players
    begin
      print 'How many players do you want to add? '
      number_of_players = gets.strip.to_i
    end until number_of_players > 0
    return number_of_players
  end

  def ask_player_class_name
    begin
      print "What kind of class (#{ALLOWED_CLASSES.join(', ')}) will player ##{players.size + 1} have? "
      player_class_name = gets.strip.downcase
    end until ALLOWED_CLASSES.include?(player_class_name)
    return player_class_name
  end

  def new_player
    case ask_player_class_name
    when 'warrior'
      return Warrior.new(ask_player_name)
    when 'mage'
      return Mage.new(ask_player_name)
    when 'thief'
      return Thief.new(ask_player_name)
    when 'custom'
      return Player.new(ask_player_name)
    end
  end

  def add_player
    player = new_player
    puts "#{player.class.name} #{player.name} has entered the game"
    puts player
    @players << player
  end

  def display_party_info
    puts
    puts "Party Info:"
    puts '-'*80
    puts "#{players.size} players in this game:"
    puts '-'*80
    players.each_with_index do |player, idx|
      puts "Player ##{idx + 1}:"
      puts player.to_s
      puts '-'*80
    end
  end
end

game = Rpg.new
game.display_party_info

thief.rb

class Thief < Player
  def initialize(*args)
    super(*args)
    @str, @int, @dex = 3, 1, 5
  end
  
  def level_up
    @str += 3
    @int += 1
    @dex += 5
  end
end

warrior.rb

class Warrior < Player
  def initialize(*args)
    super(*args)
    @str, @int, @dex = 7, 1, 1
  end
  
  def level_up
    @str += 5
    @int += 1
    @dex += 3
  end
end