       manager.play 'end' # @test
 
     _addMusic: ->
-      return if @debugging
       @music = @add.audio 'bgm', 0, yes
+      @music.mute = @developing or @debugging
       @music.play()
+      @gui.add @music, 'mute'
 
     _addPlatforms: ->
       @platforms = new Platforms 

        @gui.addOpenFolder('gravity').addRange @physics.arcade.gravity, 'y'

      # First:
      @_addBackground()
      @_addPlatforms()
      # Then:

      @_toggleCameraAttachment on

      @debugging = off # Off by default for performance. Doing this after setup.

    update: ->
      @physics.arcade.collide @player.sprite, @platforms.layer
