This is brilliant! What I really want is a list of such mathy games for my 6 year old. I found him a logic gates (XOR, AND, etc) game that he also likes.
Another one they do manage to understand (and love) is Lightbot http://lightbot.com
https://play.google.com/store/apps/details?id=com.Suborbital...
It's so good I managed to do all 135 puzzles in two days and another few hundred generated ones.
The generator might need some work. A lot of the ones it makes are too simple, solvable in 1 or two moves.