to further improve the gaming, perhaps you could add a metronome to further help with the rhythme to stroke :D
Probably won't touch this version, but for inspiration for the next game, can you tell me what you mean more precisely? is it something visible? What does it lok like and how does it behave?
IMO they are on about an audio metronome, so it would be a tick similar to an analog clock instead or in addition to the background flashing.
