The game is fine. And though you really don't need it since you can spam past levels to get the most powerful weapon early on, there is a small bug that makes this game not a problem. Have an automatic weapon and shoot till you have zero bullets, quickly change guns to something like the shot gun and switch back to your previous gun. It will start off with zero bullets and when you shoot it will have -1 bullets causing you to have infinite number of bullets plus zero reload time, which makes it the game VERY easy.