FlipSight : The Lone C-square and the Jump Trap

Aiming at a lone C-square with two footholds

The jump trap is a technique that aims at the opponent's lone C-square. You take two squares on the same edge with one empty square between them and use them as footholds. Then, whether the opponent enters the gap or leaves the edge alone, you still have a move next to the C-square that aims at the corner. However, leaving a single gap does not by itself make a jump trap.

In the position below at move 46, it is White to move, and Black G1 is a lone C-square with F1 and H1 empty. White already has E1, so playing C1 makes two footholds with one square, D1, between them. With these footholds, White can play next to the C-square on F1, or take H1 if Black enters F1. The other three corners are already occupied, so there is no exchange for the opposite corner, and in all three lines below White keeps a winning position after taking H1.

1. If the opponent plays off the edge

White to move. After White C1, 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. Use ▶ to follow White C1 → Black G4 → White F1 → Black D1 → White H1.

2. If the opponent enters between the two footholds

White to move. After White C1, 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. Use ▶ to follow White C1 → Black D1 → White F1 → Black B1 → White H1.

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

White has played C1, Black to move. 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. Use ▶ to follow Black F1 → White H1.

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, then finally check whether you can play next to the C-square and whether you can play the corner. Even with a lone C-square shape, you cannot attack it this way if the edge moves you need are not legal.