This game is very original. Great job :D
Difficult to play I like it. Also I thought it was just going to be a regular shooter but it made me think a lot and thats what help made it so fun.
Fun, but needs some bugfixes.
Nice little physics-based platformer. While the graphics may not be much to write home about, there is some charm to the game.
There were some performance issues, most notably that the game would start lagging if there were too many enemies on-screen or too many shots fired. A range limit for the alien shots may not be uncalled for.
The shotgun acceleration didn't always make sense; I could fire to the right, move a ways to the right, then stop and I would slide left. From a momentum perspective, this is a bit odd.
Collisions are hard to figure out; there were times that I landed on spikes before my feet hit them, and times when my head and neck were through the spikes that the game just didn't notice. Some tightening may be appropriate in the collision department.
If you want to make a game where death is excessively common, don't make us sit there and wait until the body finishes exploding. Two sorely-missed features were a reload button and a reset button. Sometimes I could tell I had already screwed up, but was stuck waiting to die (which usually wasn't long, but hey, why wait?), and sometimes I really just wanted to reload while it was safe, but couldn't because the weapon's kick would have knocked me out of my momentary reprieve.
Overall, a nice game with fairly nasty difficulty. There are some minor gripes, but these do not make the game unplayable.