Tristram: On the last move in this solution, (upper right corner orientation) only starting the ladder with o16 is given as correct. But concluding with s15, threatening to revive the r17 stone is arguably as good.
jhubert: O16 is more important. Probably if R15, the opponent will play O16 and let the 2 stones captured with s17.
On the last move in this solution, (upper right corner orientation) only starting the ladder with o16 is given as correct. But concluding with s15, threatening to revive the r17 stone is arguably as good.