Note to any reader. IF you use this generic Node and utilise Godot's excellent 2D Aspect Ratio stretching capabilities, you will need to swap out the get_viewport().size and replace with projectSettings retrievals of the screen size! I'll post an update to this one.

I'm just adding this to the 'Space Invaders' clone tutorial and stumbled on my mistake! Forgetting that get_viewport provides its size, not the original screen size; which I intended!