I think this game has some great promise so far. It has a really addictive gameplay loop and a good variety of levels so far. The control scheme is unique and gives the game a very "Easy to Learn, Hard to Master" philosophy. I can already see the speedrun potential once this game gets released.
I do have some issues that I believe can be amended. The enemy AI reacts way too quickly; there are so many times when I get shot even after getting to cover, and whether or not you won't get hit when moving is really inconsistent. Snipers are especially a problem (stopped playing when I got to those levels
The visuals are pretty bare-bones, which is to be expected, but I believe it can be improved pretty easily. I really like the visuals in the early Prototype; the grey backgrounds give off a very nostalgic vibe akin to the old stickman animations, and the color gradients on the enemies help them stand out and make the game more visually interesting. Audio could also use some more meat; definitely consider adding music (perhaps stock if you can't find a composer), or just add more sound effects (Footsteps from the Prototype come to mind).
So far, I think you've created a solid gameplay foundation; all I would recommend is to tweak enemy reaction times and add more to the Audio and Visual Department.
Love the Demo, Best of Luck.