Tsumego Hero
  • White to kill (find the best ko)
    Sprint Intuition Rejuvenation Refinement
    4d (2457)



    YuriyStepanovich:
    g1-f1-d1-a6-a3-a4-e3-a5 Black dead, but message is "Incorrect". Why?
    19. June 2025
    19:59
    John:
    Another variation also seems to be wrong: G1 F1 E1 H1 C1 E3 H2 F1 A6 A3. This is double ko (A4 and G1), defender is dead. A3 should be at E4, leading to a direct ko at G1.
    caranthir:
    Looks like it's been fixed according to your proposal.
    10. August 2024
    18:26
    John:
    I agree with heron, there is something wrong with variations here. As he mentioned, E3 cannot be played - attacker plays A4, finishing the ko, and defender is dead. Hence counting E1 as an ignored ko threat, this yields A+3KO, isn't it? The variation G1 F1 D1 H1 A6 A3 A4 also seems to be wrong, due to the same reason. Moreover, it seems that defender should play C1 instead of H1, as in the D1 C1 variation.
    John:
    Finally I got the solution. I changed the status of the branch after A3 A4 to A+2KO+2, since defender needs one more ko threat. The variation in my next comment has also been corrected. Please, recheck.
    10. August 2024
    11:02
    heron:
    Yea, the sequence I said below seems like it should end a move earlier? Because when the refutation plays E17 it should instead play a ko threat, or else they die.
    John:
    Defender responses were corrected. The sequence you provided is not the optimal one.
    17. April 2024
    02:17
    heron:
    Something seems wrong with this one to me: I played G19 F19 E19 H19 H18 F19 C19 G19 A14 A17 A16 E17 A15 and it says "incorrect", but defender looks totally dead, not even ko. I'm not sure my sequence is very good but there must be some error in the solution.
    10. April 2024
    04:01
    YuriyStepanovich:
    Bg1-Wf1-Bd1-Wh1-Ba6-Wa3-Ba4-We3-Ba5 kills the White, but message is "Incorrect". Why?
    Ivan Detkov:
    This is incoherent. Could you please use capital letters and avoid colors (B and W). Check the answer of posetcay down below for an example.
    19. March 2024
    18:40
    YuriyStepanovich:
    After Wg1-Bf1-Wd1-Wa6-Ba3-Wa4-Be3 Wa5-Bany-Wc1 White kills Black, but Wa5 marked "Incorrect", why?
    23. February 2024
    09:27
    kovarex:
    This problem is now the prototype as a status-based problem. This means, that the branches are not marked as correct or incorrect by + comments, but instead, there is specification of the status, and the applet automaticallly assigns the correct branch based on the best possible status. This is to show that the correct variation is A+3KO (3 approach move ko), while some other, similar variations are not good enough, as they might be only A+2KO (2 approach move ko) There are still tweaks to be done (mainly to show the full-text status explanation in the review mode), but it seems to work nicely as a prototype.
    d4rkm4tter:
    Very good. I want to make a special topic collection with this.
    13. September 2023
    17:16
    posetcay:
    Also added a stone outside to remove N1-M1-O1-Q1 possibility.
    25. July 2023
    13:54
    posetcay:
    The solution is correct, but opponent's refutations were wrong in many places. For example, R1-Q1-N1 should be answered by M1 and R1-Q1-T2 should be answered by P3 etc. Made the necessary corrections.
    25. July 2023
    13:32
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