I still have a problem though.
I got the ground moving, but to keep it running I need to change the gravity to zero. But everything around is affected.
How do I change gravity individually per object?
My project is based on two oposite gravities, up and down, and diferent objects must fall in oposite directions.
With box2d I can't do this, and I though I could do this with the chipmunk, but I don't know how.
thanks in advance for your help