I agree with what secondtime wrote for feedback....something that bothered me when I first started playing was that it seems like the ball stays still and the stage moves when you jump...which was messing with me and I died constantly in the beginning levels. Even watching the youtube video that is linked I find myself watching the background rather than the ball...maybe its just me but I think the stage should stay still and the ball should jump up rather than the ball stay still and the stage move down.
I understand you quite well, I thought of this effect might happen to somebody. It's just that even though the levels seem to go just from left to right, later levels start to have a lot vertical moves as well. In those cases, the ball have to stay fixed and the background should move. This would make 2 different mechanics in those cases and I think this will confuse a lot more. I'm not sure what I can do about this but will think about it... As usual, thanks for sharing with us