This is a well programmed and designed game. However, there are two problems I see with it right off the bat.
1) You've programmed it so that the Human can't shoot through walls but the CPU can. That's fine and it isn't the only game that does that but, if you run up against a wall and the gun is in the wall you're able to shoot through. But that really isn't that big of a deal just a little something.
2) The final world levels that end in boss battles should have a shortened level leading up to the actual boss. With challenging boss battles like the ones in this game it can be maddening to get though the level and only have one health bar left to face the final enemy.
Other than that this is a very well made game, kudos.