This game is pretty damn bad. It's extremely annoying leveling up and getting skills when there's only two possible enemies you can fight and you continuously get one that you just can't beat. Losing experience doesn't help, either. Getting the last badge is incredible boring, as all of the classes are nearly the same.
It's kind of a pain to place things how you want with the gravity gun. Also, enemies should be crushable and shouldn't be immune to everything but the player's own guns.