I fairly simple inversion, but it works pretty well.
It looks like we both took a classic video game, made the 'original player' AI controlled, and had the player control what in the original game was trying to destroy them. I did it with Asteroids, you did it with Space Invaders.
(minor bug: when you click start and the two sliders appear, the bottom slider says 'invader count' instead of 'defender count' until you drag it, after which it switches to 'defender count')