Chain Shooter is available now on the iTunes. It looks like a nice little Shoot 'Em up game.
Game Description: Players (Minjas) must protect humanity from invaders, using unique game controls to control a space vehicle and fight against colorful invading creatures. Players earn points (and save humanity!) by correctly coordinating attacks in accordance with the conventions for (mathematical) order of operations, or PEMDAS.
Pedagogy: Gameplay focuses attention on recall and repetition of the PEMDAS convention (parenthesis, exponents, multiplication/division and addition/subtraction) encouraging correct recall of order of operations.