Good and clearcut
This is a game that works very well because you are really able to simply go out and do what you need to. At first, I thought it would be more like an RPG and I am glad it was not. The best thing is that you give your player a lot of room to go around and shoot those aliens. It definitley gets a lot harder as it goes on and quickly. You have to form strategy by specifically looking at how the guys are coming. It seems to be realistic as you can not just shoot wherever you want and bullets do not go through the background when firing.
It was also fun to just shoot those little bushes and trees while nothing else was going on. The designs of the aliens are good, but need to be a little fancier. The music was also fairly fine. I like how you have such a large space to go and fight so you can form strategy by running to a different part of the level. The sound effects seem in order too.