按照《Ruby 从入门到精通》敲了一段代码，执行提示：

核对代码，没有敲错，谁能帮忙指出问题在哪，如何解决？具体代码如下：

class Dungeon
  attr_accessor :player
  def initialize(player_name)
    @player = Player.new(player_name)
    @rooms = [ ]
  end
    def add_room(reference,name,description,connections)
      @rooms << Room.new(reference,name,description,connections)
    end
    def start(location)
      @player.location = location
      show_current_description
    end 
    def show_current_description
      puts find_room_in_dungeon(@player.location).full_description
    end
    def find_room_in_dungeon(reference)
      @rooms.detect {|room|room.reference == reference }
    end
    def find_room_in_direction(direction)
      find_room_in_dungeon(@player.location).connections[direction]
    end
    def go(direction)
      puts "You go" + direction.to_s
      @player.location = find_room_in_direction(direction)
      show_current_description
    end
  class Player
    attr_accessor :name,:location 
    def initialize(name)
      @name = name
    end
  end
  class Room
    attr_accessor :reference,:name,:description,:connections
    def initialize(reference,name,description,connections)
      @reference = reference
      @name = name
      @description = description
      @connections = connections
    end
    def full_description
      @name + "\n\nYou are in "+@description
    end
  end
end
my_dungeon = Dungeon.new("Fred Bloggs")
my_dungeon.add_room(:largecave,"Large Cave","a large cavernous cave",{ :west =>:smallcave })
my_dungeon.add_room(:smallcave,"Small Cave","a small,claustrophobic cave",{ :east =>:largecave })
my_dungeon.start(:smallcave)
my_dungeon.go(:west)