Prototyping The Game - Developing Games With Ruby - page 48

$window , "Q = Quit, #{ continue_text } N = New Game" , 30

Gosu . default_font_name, 30 )

31

32 end
33
34 def draw
35 @message . draw(

$window . width / 2 - @message . width / 2 ,

36

$window . height / 2 - @message . height / 2 , 37

10 ) 38

@info . draw(

39

$window . width / 2 - @info . width / 2 , 40

$window . height / 2 - @info . height / 2 + 200 ,

41

10 ) 42

43 end
44
45 def button_down ( id )
46 $window . close if id == Gosu :: KbQ
47 if id == Gosu :: KbC && @play_state
48 GameState . switch( @play_state )
49 end
50 if id == Gosu :: KbN
51 @play_state = PlayState . new
52 GameState . switch( @play_state )
53 end
54 end
55 end

It's a Singleton , so we can always get it with MenuState.instance .

It starts playing menu_music.mp3 when you enter the menu, and stop the music when
you leave it. Instance of Gosu::Song is cached in @@music class variable to save
resources.

We have to know if play is already in progress, so we can add a possibility to go back to the
game. That's why MenuState has @play_state variable, and either allows creating
new PlayState when N key is pressed, or switches to existing @play_state if C key
is pressed.

Here comes the interesting part, implementing the play state.