 
       @_initDebugMixin()
 
+    # Public
+    # ------
+
     addImages: (nameTemplate, topZIndex, bottomZIndex = 1) ->
       @topZIndex = topZIndex
       for zIndex in [bottomZIndex..topZIndex]

      # @group.y = -(@group.height - @group.game.height)

      # Set vertical scroll factor and offset.
      nearest = @nearestLayer()
      farthest = @farthestLayer()
      for layer in @layers
        {image, zIndex} = layer
        # Factor in z-index exponentially and constrain.


      @debug 'layers', @layers

    # Helpers
    # -------

    _farthestLayer: -> _.findWhere @layers, { zIndex: 1 }
    _nearestLayer: -> _.findWhere @layers, { zIndex: @topZIndex }

  _.extend Background::, Helpers.DebugMixin

