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#1: Liz P (lizteach) on Jan 22, 2011 [HINT] [SPOILER]

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is it really straight smile logic?
you still have unaccounted for cells in the nose area
i am not sure about this one

After the "eyebrow" login the rest solves including the nose.

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I mis-wrote. What I used was not smile logic. It was two-way logic; at least, I think that's what I mean.

So using the "purple logic" term, when you run out of purple logic, and have only the nose and eyebrows left, you should be able to use two-way logic on the 1 in C6. There's a choice between R2 and R4. It has to be in R2 because placing it in R4 means that you can't put a row of 3 in R2. Perhaps that is a bit of a look-ahead, but I thought it was a fairly obvious one (certainly no more look-ahead than most edge logic).

From there, purple logic solves the nose and then all is left is to do the same two-way trick on the other eyebrow.

If anyone can follow the above, I'd like to know whether it makes sense, or whether my logic is somehow faulty.

(I find the logic discussions these puzzles engender really interesting.)

(And I should add, I guess I said it was smile logic because it *felt* a bit like smile logic while I was doing it, plus, it looked at bit like an upside-down smile!) :D

I looked at your logic Liz, but I think it requires looking more than 2 moves ahead to get to a contradiction.

How about this? Looking in column 3, we have a 1 clue. It can go in either R2C3 or R4C3. Look how this affects column 5. In both cases, R2C5 will be black and R4C5 will be a dot. You can do the same logic with the 1 clue in column 19 to make R2C17 black and R4C17 a dot. The rest solves with line logic. Much easier this way.

Found to be logically solvable by Gator.

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