About the position of the sphere, I purposefully did that in order to make it more difficult to shoot through one end of a passage to another. And through game-play, I think it's pretty obvious that only the walls, and the enemies could break the sphere (and the things that are left out, i.e. the player ,and enemy orbs, can't interact with the player's sphere).
Yeah, a settings option with a volume slider would be a really good addition, but I didn't think of it, and I would have been too lazy to add it :P.
Thanks for playing.