I second that talon, and yes, if you open the editor and load any MP map or even SP map you will see transparent bricks (or walls) with a red/black stripe design, those are the invisible walls, but CoD's invisible walls are just....... -.- ... at least in MW2 they put the radiation thing so if u go out u die.... but still... it just feels so fake. And yes, i think youre right armageddon, i think they will use debris to replace the "invisible walls", and still put some invisible walls behind (or over) the debris just in case, cause when there's a will, theres a way