QUOTE(Wing-of-no-Wing @ Apr 9 2006, 05:27 PM)
You'll need two 1x1 locations. Let's call them A and B. A starts out centered on the ghost. If the player brings no ghost to A, but a ghost to Anywhere, center B on the ghost, move the observer to B, and then center A on the ghost. If they bring an observer to Anywhere but no observer to A, and a ghost to A, then it explodes.
[right][snapback]462132[/snapback][/right]
Took me a while to comprehend that...
You don't need the B location however. Just have the A location and the observer center on the ghost when he walks out of A. The location and the observer will be centered at the same time so if the player ever has 0 observers at A it will be because he moved the observer while the ghost was standing still.
PS: An observer or ghost is always at anywhere so that condition is pointless.