I never needed to use the shell, in truth I still don't know how it helps. As for the wall obstacles, since the floor detection script doesn't check for a reasonable angle, I was able to air strafe over it with relative ease. It's a simple mistake to make, but it's generally a good idea to have a different strafing speed in the air so that you can't just plant yourself into a wall by holding a key down, since in that situation there's no floor for you to push against. Same story for the quicksand stuff, as far as I'm aware there's no speed cap so you can build up infinite speed and fly over it which I did. Other than that really great game, nice modelling work especially, and good artistic direction. Just that the character controller defeats the point of the game :(