Yep, it says it on the tin, math and guns.
This could definitely be one of those games to teach kids math skills, though you probably would not find it in any schools.
I don't really like the disconnect between the shooting and the math. The split focus is a bit hard.
Solution could be that the gun aims automatically and me doing math adds ammo and/or makes it shoot.
Other than that, functional, kinda funny, and simple. Well done.