I like games that make you think, arent timed, and you dont die. This is an infinitely re-playable game.
Suggestion: Do away with level unlocking and simply allow the player to choose any game randomly. Its not like the games get harder as you progress. The achievement is in competing games, not in doing them in a certain order.
Suspicion: Some game developers are selling (as in-app purchases) the ability to skip levels, which has become a cancer on gaming. If this is the only reason for level unlocking (i.e., to eventually charge money to skip if you get stuck), I will trash this app in the reviews from now until doomsday. Sorry for that, but this trend has made me very suspicious of good games. I think, "whats the catch?" If thats not the plan, then thank you in advance, and well done.