Puzzle Description Suppressed:Click below to view spoilers

#1: Jan Wolter (jan) on Apr 17, 2007 [HINT]

This is a particularly nice example of a somewhat uncommon kind of logical reasoning. Most of the puzzle solves very easily, but you are left with sixteen unknown squares in eight pairs of two.

Let's look at the first, column. It's clue is "1 1". There are four unknown squares in two groups of two. Obviously in each of those two groups, one square must be white, and the other blank, but we can't tell readily which is which.

Let's focus on the unknown squares in the top two rows (both have the clue "11"). We just decided that one of these elevens is going to start in column one, and the other in column two, but we don't know which is which. However, if we look at the other end, it is obvious which it must be. If the top row started in column 2, and the second row started in column 1, then the column tweleve clue would hae to start with a "1". But that clue starts with a "10". That can't work. So it must be that the top row starts in column 1, not column 2.

I'm finding that when there are just two possible ways something can be filled in, that it is often possible to look ahead just a bit from that point, and either see a contradiction for one of them (as in this case) or see that they both have some of the same consequences, in which case you can fill in some of those consequences without yet knowing which of the two apply.

So anyway, I think this puzzle makes a very nice introductory example of slightly more advanced puzzle solving techniques.

The unusual logic in this puzzle was pretty fun.

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Wouldn't red have been better?

probably but at the time I was doing only black-and-white puzzle so that's why

Either way works for me. :)

This is also an example of extended smile logic. The 1,1 in c1 pairs with the unfinished 10 in c12 to make a "smile". Then one can see that the 1,(2), 1 in c5 pairs with the unfinished 10 in c16 to make another smile.

This was much more fun than it looked!

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