Simple, fast, but curious concept nonetheless.
I guess there's no end point to the game (as for now) or I'm just low IQ :p
Anyway, I've enjoyed it!
PD: You have a bug when pressing the tab. The game crashes if you press it more than two times (as there's only two levels). You could either check that no more than (# of levels) presses are taken into account, or use levels % (# of levels) when indexing the level list.
Cheers, and good luck! :)