The double-cross

The lesson in words

Your opponent opened the three-box chain along the top. If you take all three, it’s your move again and you must open the six-box chain: your opponent takes six and wins.

The double-cross: take one box, then give back the last two.

First, take the box that’s already been given to you.

Try it: Take the first box.

Two boxes are left in the chain. Instead of taking them, draw the line at the far end of the row. That leaves both boxes for your opponent, joined by one line.

Try it: Hand the last two boxes over.

Two boxes given away can win you the whole next chain.