Four stars for being rather daringly original and different from the usual game.  Also for making the player figure out what to do on his own rather than having a tutorial that explains everything.  Gives a fun sense of discovery as the player figures things out.  

Minus one star for succumbing to a trope of platformers: monsters or machines that 'kill' you if you mess up or don't progress across the level fast enough.  At least there isn't a timer.