We need a lot of ideas to start with, so we can choose the best to develop into the final game. So my thoughts on what to do is as follows:
I've got three words that i'd like to describe the final game with:
One game could be about motor-/coordination skills , where you can train yourself into a rythm so that one can master operations that look impossible from the outset, like DDR or similar games. The interface needs to be simple.
Another game could be more a twist on existing 3D racing games. But instead of going for realism, the enviroment and physics should be more abstract or surreal. A lot of the games out there does not embrace the possibilities of the more fantastic enviroments you could make in a computer game, like in LocoRoco.