I would provide your control button array by creating an image of the Buttons you require as a single png image consisting in ALL the buttons. Each 'button' has a slightly different background color (see advice below). In your case, it would be subtle shades of charcoal gray perhaps. Place the image in a Canvas. Construct your 'button array' as described in this example Button placement(How to use Canvas screen colors to create a Q&A Quiz . You select a 'button' by using the Canvas.GetBackgroundPixelColor Block.
I think this method will work with a Responsive screen. You could try it. (your global dimmer might create an issue...provide it separately?)