Comments on Puzzle #34642: Droodle #13
By Bill Eisenmann (Bullet)
peek at solution solve puzzle
version: 3 quality: 
difficulty: solvability: moderate lookahead
peek at solution solve puzzle
version: 3 quality: difficulty: solvability: moderate lookahead
Puzzle Description:
Answer in first Spoiler
#1: Bill Eisenmann (Bullet) on Oct 30, 2020 [SPOILER]
Jack out of the box.#2: Kristen Vognild (kristen) on Nov 1, 2020 [HINT]
Credit Roger Price
When you created this, did the checker say it was logically solvable? I had to resort to symmetry, when I got to the upper middle section.#3: Web Paint-By-Number Robot (webpbn) on Mar 22, 2022
Found to require some guessing by gator.#4: Gator (gator) on Mar 22, 2022 [HINT]
Too much lookahead even for deep. Marking as guessing.#5: Web Paint-By-Number Robot (webpbn) on Mar 23, 2022
New version published by Bullet.#6: Bill Eisenmann (Bullet) on Mar 23, 2022 [HINT]
Does this edit help much? I think you still have to assume symmetry ...#7: Kristen Vognild (kristen) on Mar 23, 2022 [SPOILER]
I think if you added a black square to R10, C7 & C13, that would do the trick.#8: Susan Nagy (susannagy54) on Mar 23, 2022
Like Kristen, I also resorted to symmetry.#9: Web Paint-By-Number Robot (webpbn) on Mar 24, 2022
New version published by Bullet.#10: Bill Eisenmann (Bullet) on Mar 24, 2022
Ok Kristen. I think you nailed it!#11: Philip (Philip) on Mar 24, 2022 [HINT]
I still can't get it without guessing:#12: Wombat (wombatilim) on Apr 15, 2023 [HINT]
LL/CL
Deep lookahead? if R4C13-14 is black, then R4C15 is a dot and R3C13 is a dot, causing R3C14 to be a dot, causing R5C14 to be black, causing R5C15 to be a dot. Those dots contradict C15, so R4C13 is a dot.
Same pattern applies if R4C6-7 is black, so R4C7 is a dot.
LL
EL: If R3C4-7 are dots, then R5C5 and R5C7 are black, contradicting R5. Thus R3C7 is black.
Same pattern applies if R3C13-16 are dots, thus R3C13 is black.
LL
Deep lookahead? if R5C6 is black, then R3C6 is a dot, causing R3C5 to be a dot, and R5C5 is a dot, contradicting C5. Thus R5C6 is a dot.
LL
Deep lookahead? if C5R6-7 is black, then C5R8-9 are dots and C6R6-7 are dots, causing C6R8-9 to be black, causing C7R8-9 to be black, contradicting C7, so C5R6 is a dot.
LL
Deep lookahead? if C6R6-7 is black, then C6R8-9 are dots and C5R7 is a dot, causing C5R8-9 to be black, causing C4R8-9 to be black, contradicting C4, so C6R6 is a dot.
LL
EL in R7: the left-side 1 in R7 cannot be in C6, it would contradict R9. Thus R7C6 is a dot.
LL
At this point I couldn't find any contradictions few enough moves ahead that it wasn't guessing.
R4: If C6-7 are black, R5 C4-5 and C7-8 would be white. This makes C5 invalid, so R4C7 is white. Minimal LL.#13: Web Paint-By-Number Robot (webpbn) on Apr 15, 2023
R4: If C13-14 are black, R5 C12-13 and C15-16 would be white. This makes C15 invalid, so R4C13 is white. Minimal LL.
C5: Whether the first 2 goes to R3 or R5, R5C6 is white. LL.
C16: If R11 is black, R4 and R8 in C14 are both black, and R6 is invalid. R11C16 must be white.
R4: If C16 is black, R8C14 is black, and then C14 will need to be completed with R7 and R10-11. This puts black in R9C15, which makes R9 invalid. Therefore R4C14 is black instead.
LL to finish.
Found to be solvable with moderate lookahead by wombatilim.
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