Maybe it'll be something like Chaotix, which had a day/night cycle. Enemy and item placement also changed. Green Hill Zone at sunset (ala Advance 3) and Mirage Saloon Zone at night? Metallic Madness Zone in the Past and Good Future? Metal Knuckles in Stardust Speedway Zone? Badniks in Zones they're not usually found in? A little disappointing that there won't be any new levels, but hopefully that just means they're saving them for a sequel.