Well it looks like it will be a badger month for me. I am 1 episode away from finishing it (Gravity Badgers). This game started out pretty simple, but around Episode 4 it gets pretty challenging. In the fun, I want to replay this level 100 times way, so it's a good kind of challenging.
The Episode 4 boss battle is pretty crazy. Took me a good many tries to get down the pattern before I could pass it and then some more before I got through it without getting hit once.
It's definitely a casual game since all you use is the mouse, but Episode 4 and 5 get pretty challenging. If anyone is a fan of Angry Birds space, this one will be right up your alley.
I remember watching Carlmundo playing it and being disappointed it was so casual, but it definitely pays off if you stick with it. By the looks of it I should be getting almost every achievement. Don't know if I'll get the play 10 hours plus one since I'm at 4.3 hours and almost done with the game, but maybe I'll idle it just to finish that one off.