It's clear that work was put into this, but some things need improvement. First, either speed up the jumping animation or slow down the aliens rate of fire. Next, the first alien you encounter seems to have too much health, as I had to pound him with fire for almost thirty seconds before he died, whereas all the other aliens like him died much faster. I like your ideas for hiding in shadows and stuff, would like to see more of that in games like this. Also, I'll only briefly mention that there is a game called Alien Carnage, but I see the most recent reviewer already pointed that out so never mind. Nice work.