I know it's a demo... Work on these:
1) The characters. Kinda dodgy drawings. More detail on them, and maybe things like more than their feet moving. Run animations as well as walk, recoil from firing, aiming?
2) With the sniper, if I stood on a platform above Lincoln, I could still shoot him.
3) Controls are too slidy and the jump is overpowered/
As soon as all this are fixed, it could be okay.