One minor gripe
Rolling the ball up or down ramps became frustrating because the direction of the ball wasn't influenced by the actual slope. This is slightly hard to explain so I'll give you a way to demonstrate the problem for yourself.
1) Position the ball on one of the grided lines (the white/green ones) somewhere near a ramp going up.
2) Quickly press both buttons to move the ball directly up the ramp. Make sure you are traveling perpendicular to the edge of the ramp.
If done correctly in the context of this game the ball *should* follow the line it started on and the direction of the ball should change slightly as it is percieved as a 2d object. WHat actually happens is that the ball continues in the exact same direction (according to a 2d perspective) even once it is on the ramp. Even though the ball should stay on the line all the way up and over the ramp it immediatly strays and can cause the ball to fall off for no reason.