FlipSight : Reverse Parity: Leaving a Square the Opponent Cannot Enter

One pass changes who plays the last move. So Black keeps a square White cannot enter empty until the end. If Black plays so that, apart from that square, every region is even after each of its moves, White has to enter even regions first and Black plays the last move of each region. When everything else is filled, White passes and Black plays the last move on the square left empty.

Playing the saved square first throws this effect away. Also, a square White cannot enter now is not always closed until the end, so check that your moves elsewhere do not give White a foothold for that square.

Black to move. A2 is a 1-square region White cannot enter. Black leaves A2 and plays A7, turning the 3-square region into 2 squares so that the rest is all even (2 and 4 squares). Afterwards Black plays the last move in each region White enters first (B8, H8), and after White passes Black plays A2. Black loses by 2 discs, but playing A2 first loses by 14.

Exercise

Black to move. Of the marked H3 and H7, choose the move that leaves the square White cannot enter and plays elsewhere.

Exercise

Black to move. Of the marked E2 and G7, choose the move that leaves the square White cannot enter and plays elsewhere.

Exercise

Black to move. Of the marked B8 and H2, choose the move that leaves the square White cannot enter and plays elsewhere.

Exercise

Black to move. Of the marked G8 and H3, choose the move that leaves the square White cannot enter and plays elsewhere.

Exercise

Black to move. Of the marked A3 and B2, choose the move that leaves the square White cannot enter and plays elsewhere.