what about it being a bot with a density of 0 so it floats in the air, and space adds 1-5 velocity like GSF's did, and the TBH, and heed's, and then shift to add -1--5 velocity to go down, and another key to set velocity to 0? that or press space to increase a velocity counter and shift to decrease, and the number the counter is the velocity up/down is?
another thing is what about a hang glider like the one bushido made, but with propulsion? it would be easier to fly then :D