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#1: Levi Ross (rhodyboy888) on Dec 23, 2008

I guessed. Maybe it is solvable with logic. If so, I couldn't figure it out.

same here. You definitely need to guess.

I had to guess but simply used symetry.

Maybe a little bit of edge logic involved when interpreting the symetry but it was a guess (at the top). Once that was done the rest solved it's self logically.

Symmetry. Shay wins the best overall 10x10 puzzles. These are nice and fun.

I had to guess that the top line was symmetrical.

Requires no guessing whatsoever. The numbers clearly show the puzzle to be symmetrical, then everything falls into place easily.

There's been a pretty involved discussion as to whether or not symetry can be a sort of logic. It's been supposed that a puzzle could be created where the clues portray symetry but the solution does not. Me - not quite good enough to make a decision either way.

Here is a way that does not use symmetry. Once you are done with line solving, focus on row 5. Of the 4 cells left, you have to fill in 2 of them. Notice how this affects row 4. No matter how you fill in row 5, R4C5 and R4C6 will always be dots. More line logic.

Now look at column 2. Either R1C2 or R2C2 has to be filled in. In either case, R2C3 will be a dot. The same logic can be applied for column 9 to make R2C8 a dot.

Now look at row 2. The left 1 clue will either have to go in R2C1 or R2C2. Again, in either case, R3C2 will be a dot (same for R3C9). The rest solves out normally.

Found to be logically solvable by Gator.

One of the best situations of logic applied to a puzzle from you, Gator. I had to solve this puzzle again after seeing your comments.

I think the size of the puzzle helps in finding this kind of logic. On a larger puzzle I would probably give up sooner.

I was actually surprised to find that there was a logically way forward on this one.

I agree that one of the charms of smaller puzzles is that greater levels of difficulty seem tolerable.

If you somehow knew for a fact that the puzzle had a unique solution, then using symmetry would be 100% logically sound. For most puzzles on this site, the pbnsolve program has already been run on them and has flagged them if they don't a unique solution, so I suppose you COULD say that you know it has a unique solution and run with the symmetry, but that's just saying that some computer program has already done a brute force trial and error analysis to determine if the puzzle is unique, so you can use symmetry to avoid having to do a brute force trial and error solution yourself. Seems kind of icky to me.

So our convention here is to treat "symmetry" as an inadmissible technique for logically solvable puzzles. An exception that I've allowed is if they author of the puzzle provides additional information about the how to solve it in the title, like [has unique solution] or [symmetrical]. Then, since this is given to the solver with the puzzle, the clue can be part of the puzzle.

I suppose you could design puzzles with other variant rules, like "at least one white between any two cells of different colors" and put those in the puzzle title too.

Excellent puzzle!! I fought the urge to use symmetry for solving and eventually found (or perhaps stumbled into) some if-then's to move it forward. Shame on all you symmetry cheaters! ;-)

Challenging & fun! Like many other little puzzles, this definitely deserves more than the 2 rating it currently has.

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