Good game. I absolutely love the concept, but I noticed mainly 3 problems with this game:
1) At some point it becomes boring. I mean, I didn't even know if this game has several levels or only one, and after a few shots (unsuccessful and a bit frustrating) I realized that I was a bit bored.
2) The controls are not 100% clear, that is, I understood that W,A,S,D are used for movement, but during the game I realized that if I right click, I focus better (which helped me to aim better).
3) In my opinion, the gun moves too much... I could understand if it moved a little from the target, but in the case of the game it seems that I consumed something before. (no offense, but it seems to be moving a little too much).