Very satisfying to mow down hordes of aliens! Surprisingly well polished game, good job!
I was surprised to see that there is next level, no idea it was coming - if my brother didn't want to keep on playing, we wouldn't have discovered it! Don't hide such big features like more levels :D The waves felt a bit tiresome after a while, searching for those last 5 aliens that fell into a hole somewhere is not much fun. I wish you could change the sensitivity! And controller support would be great, personally games like that are much more enjoyable with a gamepad.