Ivan Detkov: Sorry, A19 meant to be A17. Here is my hopefully correct statement. The group is alive after B18A17D18E18C19. Move C19 is much better than D19, which is currently considered to be a solution.
posetcay: Added your unconditional life solution and seki solutions got automatically marked as wrong.
Ivan Detkov: S18T19Q18P18R19 is considered bad but it is alive and Q19 with all these complexities lead to seki. Guile, do you agree?
guile: I added this tsumego in the L shape Collection with the variation of Ivan that makes good use of the extra liberty on D4. The same tsumego with D4 filled is provided too. It allows the player to explore the big impact of this subtle difference.
guile: Added a continuation showing that a seki can be forced but that it is bad for the opponent because gote (otherwise too many external libs and oshi-tsubushi allows life).
d4rkm4tter: Awesome. Nice use of the status list. I added statuses for the incorrect branches. Seki in gote is worse for the opponent than let the player live but get sente. That is something to think about.
Added your unconditional life solution and seki solutions got automatically marked as wrong.