Here's one the other way around—you have to minimise the chain, not

maximise it. Again I would imagine that strong players know instinctively

what to do here.

6 + + +-+-+-+  |   |b|b|b|5 +-+-+-+-+-+  |r|r|r|b|b|4 +-+-+-+-+-+  |r|r|r|b|b|3 +-+-+-+-+-+          |b|2 + + + + +-+          |b|1 + + + + +-+  a b c d e f

Blue is 3 up but now, if and when the bottom left region forms a chain,

he'll not be the one taking it. He has a unique winning move.

wcc

This puzzle seems much easier than the other 4x2 puzzle. Blue's move at c2-c3 must win. If Red does not stop the quad then Red loses. The only Red moves stopping a quad are

1) d2-d3, a clear loss for Red, as Blue gets another 2 points in the north or

2) d1-d2.

Blue replies to the latter with c1-c2. Now Red must stop a second chain. She'll sack two boxes in the 2x2 Icelandic corner to do so. There are other lines of play in the corner, but they all lose…

I am surprised that this is the unique win, so perhaps I have made a mistake…

Sam: you're right in everything you say above (apart from the suggestion that you've made a mistake). I think the reason this one got me excited was that there was only 1 winning move. To be honest, I think that I had never thought about “defending” a 4x2 before and hadn't really realised that the defender, if moving first in the region, had such a powerful move. The computer says c2-c3 is the unique winning move; if you want to suggest other moves I will suggest responses (to save you having to work the trickier lines out by hand, if there are any tricky lines at all). Did you try the maximising one? I would have got this one wrong; I usually play 4x2 corners in a certain way and the example I posted is a case when this way doesn't work.