Dots and boxes problem #513

The task

To move

Dark

Difficulty

Medium

Goal

take 4 of 6 boxes

6 boxes are still unclaimed. The best line gives the side to move a margin of 2. A 4 × 4 board in the chain phase. Count chains before you draw anything.

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.