Thanks for the feedback!
I'm aware that the level design is very much rushed. Not having enough time to tune the levels, I took the decision to have a few more enemies on some points to create areas of high conflict, followed by an hidden health restore bonus (the beer) to create an appealing interest curve and motivate players to kill all enemies and barrels in quiet zones.
After the game jam is done, I'll upload new binaries with more fair, but still interesting levels :-) But for now I keep what is there to be fair to the game jam spirit.
About the glitches, if you played the html5 version I apologize as it wasn't tested at all during development: it was just added to allow more people to rate the game during the jam on the assumption that it would be good enough. However it looks like many people prefer the html5 version over the downloadables, so I'll take better care of it next time and playtest it continously during development.