I have a soft spot in my heart for the super duper simple sprites that do a lot of heavy lifting. The alien is very cool.
I love the weapons! blowing up gas stations with the bomb is ultra satisfying. There should be a mechanic that encourages you to space those out, because I ran out early on and then felt like the best weapon was out of the game now.
Finally, I'd slow the alien down juuuuust a little. I don't mind a little 'sliding on ice' but I think he could have a little more traction, or a little less velocity.
Great job all of you!
Adam