In the RL, no warns me before I run into walls. The pain is a good indicator that I did something wrong. :-D
I've already written that you get an optical (picture gets a red frame) or an acoustic warning (for example a sound like an electric shock). A solution of course would be to make everything black as long as you don't return to the starting point. The game Budget Cuts does this quite cleverly by fading out almost all details and turning everything green. Spying doesn't work with it: (This can only be seen for a short time, I have not found a longer example.)
Too bad that the stairs / ramps don't work. I would like to try that.
BTW: I found the video here where someone plays TFG in a very big playspace, if you don't already know that:
