It would really depend on how different the levels are from one another. Staying in the same world and using code to do possible actions, like (1) remove the current actors from the world (2) change the background image and (3) add the actors for this level into the world, would keep all your world fields intact (they would not be reset by starting a new world). That could be quite messy, though. As an alternative, you could have your levels extend my Super Level Support Class superworld which could be beneficial on many aspects of your program.