Good idea, bad execution.
This was a great idea for a game, but I don't think you went about it that well.
I was surprised by the green tanks, because I expected something simple, like multiplication or division to follow. I'm surprised you didn't add that in, because... math? Or maybe simple squares and other powers. And then move your way up to quadratics. But you jumped straight from 5th grade patterns to 8th grade quadratics. Weird transition much?
I also know for a fact that I did all the quadratic equations right, but the game wouldn't accept my answers. I had to plug in the negatives of every single answer to kill the green tanks. Check your math. Reading the other reviews, it doesn't seem like I'm the only one with this problem.
Also, about game play itself, there were too many places to get trapped. I'm disappointed when I saw that there were no "shops" or "power ups" which could help out. How stupid is it to get shot by the tank that you just blew up?!
Game play was too slow.
But it was a good concept. Maybe for WMD2, you could take these comments into account.
Otherwise, it was pretty fun.