FlipSight : Openness and the Center Split

The lower the openness, the fewer new footholds you give the opponent, because empty squares next to flipped discs easily become the opponent's next moves. It is a different criterion from the number of legal moves available right away.

Black F4 flips five discs: C4, D4, E4, E5 and F5. Counting the empty squares next to them, B3, D3, F3, G4, B5, G5 and G6, once each gives seven squares: openness 7. Press ▶ to play it, and the counted squares are shown as blue boxes.

Center split

If every flipped disc is an inner disc whose eight neighbors are all filled, the openness is 0. Such a move is called a center split. It splits a central group of discs and flips only inner discs, so it gives the opponent no new foothold at all: the most typical quiet move.

In the same position, Black D3 flips D4 and D5. Both are surrounded by discs, so the openness is 0: a center split. The engine predicts +2 for D3, the best move in this position, and -17 for F4. Compare with the first board.

Exercise

Black to move. Find the move with the lowest openness when you count the empty squares around the flipped discs. If several moves share the same value, all of them are correct.

Exercise

Black to move. Find the move with the lowest openness when you count the empty squares around the flipped discs. If several moves share the same value, all of them are correct.

Exercise

Black to move. Find the move with the lowest openness when you count the empty squares around the flipped discs. If several moves share the same value, all of them are correct.

Exercise

White to move. Find the move with the lowest openness when you count the empty squares around the flipped discs. If several moves share the same value, all of them are correct.

Exercise

White to move. Find the move with the lowest openness when you count the empty squares around the flipped discs. If several moves share the same value, all of them are correct.