My opponent said if I had played k17, I would have won. I think they meant |7.k17. It definitely looks good on the bottom, but doesn't help much above. I would expect something like 8.j10 to follow and a wide-open game afterward.

|9.d16 was losing. I think a lot of my losses are from undershooting on what I think I've seen David call the "weakest working move". |9.f19 looks much better and still leaves a strong face toward the top. It was a while ago, but I think I checked a lot of common moves after |9.d16, like |10.f19, |10.e19, |10.e20 (Achilles), etc. But I missed |10.e21 even though it's a very ordinary 5-2 extension.

Resignation seems premature. I played a line as white against the bot. |13.e20 14.d19 15.g21 16.h20 17.i22 18.e17 19.s11 20.r16 21.h19 22.g11 23.i12 24.j10 25.k13 26.l11 27.m14 28.o12 ouch, that was clever. but maybe white can improve somewhere. I backed up to black's G11 in this line and let the bot play itself. I will post the result in the morning.

BTW if you click on the TXT button and save the file on your machine, twixtbot-ui can load the file directly, and will even display the header info. Post-mortem only of course.

White still lost. I welcome questions.

|13.e20 is the kind of move I've never thought to look for before. Is that just a potential weak spot in the 5-2? I agree, there's still a lot of game left to play if white can break through on the lower left.

Well sure, attacking an unlinked peg by playing directly above it is potentially a good move in many situations. In this situation it doesn't quite work against the bot, but you were playing a human. Your judgement in playing D16 was not so bad after all. IMO your losing move was P18. Instead you could have made some tempo threat moves on the right such as |11.t14 12.r18 13.n15 which prepares for your attack at E20, This would have made white significantly stronger when the battle moves to the top right.

Yeah, definitely agree that if the lower left is winnable by white then there are better plays on the right side. I'll keep an eye on playing right over a lone peg and see if that doesn't open up some better combinations in some situations.