Four in a row problem #510

The task

To move

Light

Difficulty

Easy

Goal

win in 2

15 discs are already on the grid. Win in two: your first disc should create two threats at once.

What to look for

• Two threats at once: one move should leave two mills, lines or captures that cannot both be stopped.
• The winning line is diagonal, the direction players tend to miss.

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.