A Simple Ball Game

Hey, smng..i saw the game ur son made and i am currently doing a game similar to that for my sch project but i am having some difficulties with the collision detection.. im using alice 2.0 by the way and I can't get the spheres to collide with one another, i have used the proximity functions but I can't get it to work properly, unless I am using it incorrectly. My character walks when the key is pressed up and backwards when the key is pressed down, it doesn't drifts with the camera view like yours and I am using Knives ( loop infinitely) as the obstacles instead of spheres, do u think that might have been the case ??