Very good game. It is lacking things though, such as:
-Crouching
-Sprinting
-A campaign
However these things are made up for the addictive gameplay, the enjoyability of the game and a sense of originality. I say keep it up.
Things to add in the sequel:
- A multiplayer/online multiplayer feautre
-More dynamic arenas/maps
- A bigger selection of guns and enemy's
In the mean time good job. You made a brilliant game.