In this chess variant, all normal chess rules apply, with one very significant change.
First, a definition: A space is said to be observed if a piece of either side could capture to that space.
 
The change: instead of a normal move, a piece which is not observed may move to any space that is not observed.
Note: pawns may quantum tunnel to the first or last ranks, but may only promote if they move to these spaces as a normal move.
 
In the early stages of the game, there is little change. As the game progresses, watch out for pawns tunnelling to the 7th rank and sneaky checkmates!
 
 
You'll find more rules files for download on Stephen's web site at http://www.scat.demon.co.uk/free.html