Also how about a straight forward level, just needing to turn gravity up and down in order to overcome obstacles while some sort of crushing wall is following you?
This would mean you have to be fast and make good use of the skills as otherwise the moving wall will get you.
This could be added for a later level, where the player already has learned how to use the character's skills properly.
In case the "moving wall" is not clear, read through the chapter "Drill wall" of the Kid Chameleon Wikipedia entry:
http://en.wikipedia.org/wiki/Kid_Chameleon_(video_game) Drill wall
There are three levels throughout the game (starting with Hills of the Warrior 1, then Forced Entry, then Bloody Swamp) that feature a giant, metal wall covered in drills and augers that sweeps across the screen at a slowly increasing pace. These levels require the player to navigate and exit the map as quickly as possible, as coming in contact with the wall instantly kills Kid. These levels have a unique music theme, which becomes useful in identifying the danger early on.
