Your proposed modification descriptions are not very clear. Be sure that any new levels you make are substantially unique from each other and the tutorial. Be sure that if you want to count new audio for significant points that you either make the new audio yourself or completely change the audio-scape of the game, in either case you should properly cite what is created by you and what you obtained from elsewhere. The same idea applies to changing the appearance of characters and enemies. Be sure to clarify what the new obstacles or pickups are and how they interact with the gameplay.