Here’s another set of interesting positions that I think the new OGS seems to handle okay right now but might be useful to consider as test positions if anything is ever changed later. I think these should all work with komi 6.5, Japanese rules.
- These are the markings OGS gives, and if scored as is, Black wins by 0.5 (3 white stones captured at G6/G5/G4).
- This is an approach ko rather than a direct ko, so Black is NOT obligated to capture B9 before the end of the game, which would result in Black losing one point of territory.
- White also has no way to win this game by playing it out because White has no ko threats. If wA8, bPass, wC9, bA9, wPass, bD9, White did force black to play it out, but White had to give away an extra capture to do so, so Black still wins by 0.5.
- These are the markings OGS gives, and if scored as is, Black wins by 0.5 (2 black stones captured at C6/D6).
- This is an approach ko rather than a direct ko, so Black is NOT obligated to capture B9 before the end of the game, which would result in Black losing one point of territory.
- In this position, white DOES have a way to win this game by playing it out. White can initiate the two-step ko, and then use the multiple ko threats in the upper right to force Black to give up something. So White should do so rather than agreeing to end the game here.
- These are the markings OGS gives, and if scored as is, Black wins by 0.5.
- This is a direct ko, so Black is not supposed to be able to get away with omitting a defense here, even though White has no ko threats and Black has multiple big enough ko threats (starting with H4).
- In this position, white DOES have a way to win this game by playing it out. White captures at A4, and then whenever Black spends a ko threat and retakes, White passes. If Black passes, White disputes the game ending, play resumes, and white takes A4 again. Eventually Black runs out of ko threats and has to defend, or else White lives.