Puzzle Description Suppressed:Click below to view spoilers

#1: Kurt Kowalczyk (bahabro) on Nov 2, 2013 [HINT] [SPOILER]

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There is some logic to finish this, but it's very deep lookahead.

After line and color logic, and the two smiles in the black, only red is left.

The 1s in r21 are the key. Whenever you have a 1 with 2s like this, you can be sure a zigzag will result.

So now you will need to pick a starting spot and then follow the zigzags that follow from that spot until you get a conflict. If you get a conflict *in both directions*, then that starting spot can be eliminated. *However - if you don't get a conflict, you cannot mark the spot at all. You cannot be sure it is the only logical spot because you started by assumption.*

For instance, we start with a red dot in r16c18 and it goes down into r17, then right into c19 then down into r18 ... and eventually you hit the 10 in r25 @ c21. So the 10 would be in c21-30 and the zigzag would head up again and there is no conflict as it ends back in r16. However, since we started with an assumption, we cannot be sure that this is the only correct way, so we must leave this spot blank and move to the next one.

If we start in r16c19, then a zig to the left conflicts in r3. A zag to the right brings us to the 10 in r25 @ c22. While you could continue over to the right like before (and get a conflict in r22 eventually), right now you can see that there is a conflict in c18 where there's no room for its 2. Since *both* directions are conflicts, r16c19 must be white.

Starting in r16c20 we get a conflict in r24 when we zig and the same r18 conflict as before when we zag. So r16c20 is white.

Starting in r16c21 we get a conflict in r25 when we zig and the same r18 conflict as before when we zag. So r16c21 is white.

Starting in r16c22 we get a conflict in r25 when we zig and a conflict in r23 when we zag. So r16c22 is white.

Starting in r16c23 we get a conflict in r25 when we zig and we cannot zag. So r16c23 is white.

And then the same, mirrored:

Starting in r16c28 we cannot zig and we get a conflict in r25. So r16c28 is white.

Starting in r16c29 we get a conflict in r23 when we zig and a conflict in r25 when we zag. So r16c29 is white.

If we start in r16c30 then a zig to the left will hit the 10 in r25 in c27. This will leave no room for the 2 in c33. We get a conflict in r25 when we zag. So r16c30 is white.

Starting in r16c31 we get the same conflict in c27 when we zig and a conflict in c24 when we zag. So r16c31 is white.

And now line logic to finish.

Found to be solvable with deep lookahead by infrapinklizzard.

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