Fun game! The scene transitions were a little jarring (sorry, I know others have already mentioned it), but I liked the variety of the levels. 

It's a bit barebone graphically, but it's to be expected for one man teams. You generally can only focus on a couple of aspects and the gameplay was one of those here. I can definitely see a game here by making this all a bit faster and maybe add some form of strafe jumping.

As for the controls, I'd say you should poll for the reload button only on key down and maybe have a cooldown ;) You can keep R pressed and never run out of ammo.

Nice one !

Quite a simple game but a nice game nonetheless !

You made quite a few levels and I wasn't expecting so many ! I really liked the last one where you played with the physics of the jump.

If I have to make a few comments, the transition from one level to another is a bit quick in my opinion and I wasn't always sure that I indeed was in a new level, but this isn't much of an issue.

One thing though, if you ever make another game similar to this one, could you ensure the ennemies die when hiting the ground ? I had to look for one or two because they had fallen hahaha