Puzzle Description Suppressed:Click below to view spoilers

#1: Jota (jota) on Jun 10, 2022

I had to look ahead!

After LL/CL gets all the red

two-way logic 1 r7: whether it is in c19 or c20, r5c20 must be white

And now it is seriously deep lookahead because of the zigzag.
If you start at the right you get all the way to the left like 40 moves later before a conflict.

Starting at the left, placing the 2 in c1 in r2-3 will create a conflict because r2c3-15, c17-18, c20 will be white, leaving no room for the two 1s in r1. However, placing the 2 in r1-2 or r3-4 has no conflict for at least 12 moves, so no whites can be placed.

In fact, that is the shortest lookahead I can find.
If we assume that the 2 in c1 is in r3-4, then it will start a zigzag leading down and to the right for 11 steps, but on the 12th in c7 it will hit a conflict as the 2 in that column would make r8 invalid. (It is a long chain, but since it's a zigzag it is feasible.) Thus our assumption must have been wrong and c1r4 must be white.

Then LL to finish

Found to be solvable with deep lookahead by infrapinklizzard.

Comment Suppressed:Click below to view spoilers

I don't recall any lookahead... just color logic

jinkies!

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