FlipSight : The Lone C-square and the Jump Trap

Aiming at a lone C-square with two footholds

The jump trap aims at the opponent's lone C-square by taking two squares on the same edge with one empty square between them. If the opponent enters the gap, you play next to the C-square and aim at the corner; if the opponent leaves the edge alone, the move next to it is still there. Leaving a single gap does not by itself make a jump trap.

White is to play move 46. In the position below, it is White to move. Black G1 is a lone C-square with F1 and H1 empty, and White already has E1. If White plays C1, one square, D1, is left between C1 and E1. Using these two white discs as footholds, White prepares to play next to the C-square on F1, or to take H1 when Black enters F1. The other three corners are already occupied, so there is no exchange for another empty corner. White keeps a winning position after H1 in all three examples.

1. If the opponent plays off the edge

White C1 → Black G4 → White F1 → Black D1 → White H1. If Black plays off the edge at G4, White plays next to the C-square on F1. Even if Black D1 flips E1 and F1, the white disc on C1 remains, and White takes the corner on H1, trapping D1 to G1.

2. If the opponent enters between the two footholds

White C1 → Black D1 → White F1 → Black B1 → White H1. Even if Black enters D1, F1 is empty, so E1 is not flipped. When White plays F1, the white disc on F1 remains even if Black B1 flips C1, and White can take H1. White H1 also remains against Black's other replies.

3. If the opponent first plays next to the C-square

White has played C1, Black to move. Black F1 → White H1. If Black enters F1 first, the black discs on F1 and G1 sit between the white disc on E1 and the empty H1, and White takes H1 at once.

Exercise

White to move. Black B1 is a lone C-square. Where should White make a second foothold with one empty square between it and the existing white disc on D1, completing a jump trap aimed at the A1 corner?

Check the order as well as the shape

Which of the two footholds to play first depends on the colors of the surrounding discs and the opponent's legal moves. If the opponent can flip the first foothold and safely enter the edge, the trap may not work. Look at both orders and the opponent's replies, and finally check whether you can play next to the C-square and whether you can play the corner. Even with the shape of a lone C-square, you cannot attack it this way if the edge moves you need are not legal.