Great game, and the first 3 levels are perfect; well paced tutorializing!
I just really wish I had read the game page before playing the fourth one, which was too long and very frustrating without knowing the glitch requirements, since neither route through the level was possible without it.
As an additional thing, I wasn't sure if my screen size was messing with my field of view. I never got a clear view of the turret and had to jump and guess the angle. I actually squashed the aspect ratio of the window to get a slightly better view.