By the way, feel free to share your own capture go problems here! To get started, play around with some random positions until you find one with a unique solution. It’s easy to make easy problems, like the one above. Harder problems are harder to come up with (duh). I would be delighted if someone could make one that I can’t solve
I still hope some other people may want to try their hand at creating problems, so here’s another tip: just look through an existing collection of go problems and look for ones that also happen to work as capture go problems.
Below are two problems that were stolen inspired from Tsumego Pro:
Problem 23
Problem 24
(click on image to go to demo board)
The fun part is that only sometimes is the capture-go solution the same as the regular solution
So assuming 3-3 dies, that leaves 2-3 and 2-2 as the remaining likely candidates to live. Hopefully someone else wants to take a crack at them, otherwise I’ll share another variation in a few days
(1 could also be at B4 I think. 1 at B5 or C4 would not work, since then black gets C3 in sente)
White must take care not to get too crazy with the second move. Connections along the side are generally stronger in capture go than regular go (since some of the normal disconnection sequences rely on sacrificing stones), but this white 2 is swallowed up by 3:
When black starts at the 2-2 point, white needs to aggressively deny the eye-shape with the second move to stand a chance. A soft white response like 3-3 fails completely, since after 3 black already has enough guaranteed eye-shape (the triangled points) to live:
The first part should be pretty easy to read without putting stones on the board, for the second part feel free to click on the image and use the interactive board
Today I randomly got curious about visualizing the winning moves for capture go on a 1-dimensional board, so I dug up my old solver and made this image:
Here the n:th row is a board with n intersections (drawn as circles for visual clarity). The black circles mark the winning moves from the empty board. The final row is n = 24.
It’s easy to see that for any odd-sized board (n > 1), “tengen” is a win, while playing right next to tengen is a loss. (Exercise for the reader: why?)
Harder question: Is it true that for all n > 7, moving at coordinate 2 is a loss, while coordinate 3 is a win? I think this is probably true, and likely not very hard to prove, but I didn’t prove it myself yet.
In the last five rows of the figure, the only losing moves are coordinates 1, 2 and the one adjacent to tengen on odd boards. Does this pattern continue indefinitely, or will there be some more interesting stuff happening?
It could be a fun challenge to solve larger boards. I think with the right optimizations even a board of size 100 might be doable!