Editing the Scene

http://gamesalad.blogspot.com/2010/06/how-to-edit-way-scene-looks-in.html

When you enable autorotation, you will need to create a scene that is 768x1024 in portrait mode.

this is where you change those. Also, you can add "gravity" in this scene, so that all the objects appeared in this scene has gravity either pulling your actors or pushing your actors.

the "Wrap Y" will allow your actor to leave the scene at the bottom and come back from the top.

of course, you need to handle the accelerations. otherwise the actor will keep on accelerates.