Copyright (c) 1995 Eric Remy
The game is played on a 9x9 torus board (i.e., there is no edges).
I would include to the original rules, that a stalemate is a loss, since it may occur that both stones are trapped inside a mutual area, and if adjacent to each other, they may never be surrounded just by walls!
If White play at d2, Black must move c2-c3, to avoid defeat.
Cell c3 is a seki point, i.e., both players would loose if they placed a wall there.
There is a similar game, called Entrapment designed by Rich Gowell, more complex and probably more stable. There are three stones, called Roamers, with more freedom of movement. Check the full rules. There is also a Zillion's ZRF to play Entrapment. Another similar variants are Alcazar, Blockade, Cul-de-Sac and Quoridor.