Dots and boxes problem #509

The task

To move

Dark

Difficulty

Easy

Goal

take 5 of 9 boxes

9 boxes are still unclaimed. The best line gives the side to move a margin of 1. A small board near the end. Decide whether to take or to decline.

What to look for

• A sacrifice: giving material first is the only way to force the result.
• Give away two boxes so that the opponent cannot decline them.
• The right move opens a chain on purpose.
• Control: make your opponent open the long chains.

How the answer is checked

There is exactly one first move that forces the result; any other first move allows the defence to escape. Moves that keep the forced result are accepted later in the line, and a move that loses it is taken back with a short note.