Puzzle Description:

#1: Billie Patterson (bpat) on Jun 24, 2010

Is there a way to solve it without guessing? I had to guess at the step pattern in the bottom left.

you have to do edge logic on c-20

I solved it using edge logic. Nice image Tom

What is it?

I would call this more like affirmation logic than edge logic. Edge logic only let's you make R20C20 a dot. This let's you fill in R14C20. Now if you look at every possible place the 6 clue can go and you see how this will affect column 19, in every case R9C19-R11C19 will be dots and R12C19-R13C19 will be filled in. You can now do a little more line logic.

This still doesn't get us to the end though. I'll work on this some more tonight.

I should put this sign on my computer at work. Except that I work at a church...

lol Cynthia
thx Gator

Gator, I got stuck after filling in R14C20, with a dot in R20C20. If I look at all the possible placements of the 6 in C20, there are six different possibilities. I don't think that is looking ahead one or two moves, but it requires holding a lot more info in short term memory than I am capable of. I had to use trial and error just to follow your hints.

I also used edge logic with the 7 & 5 at the bottom.

I wish everyone would "Stop screwing around" and thank Tom for a good puzzle.

Oh, I finally got it. It's a rebus.

thx jay lol

OK, here is a different way to tackle this one.

After the initial line solving, look at the 7 clue in row 19. It can be in columns 9-20. Starting at column 9, it would have to be in R19C9-R19C15. If you look how this affects row 18, it would cause R18C11-R18C13 to be black which makes row 18 invalid. So R19C9 cannot be part of the 7 clue (but it's not a dot as it could be part of the 3 clue). Moving right, the same logic will make R19C10 and R19C11 not part of the 7 clue. This lets us make R19C16-R19C18 black. More line solving.

Again looking at row 19, we have two 3 clues to place. If they are to exist all the way right as possible, they would have to go in columns 6-8 and 10-12. Looking at column 18, we can see that the two blacks already there have to each be part of a 3 clue. Now look at placing the 3 clue in row 19 in columns 10-12. Notice how this would make R18C11 and R18C12 be black. But this makes row 18 invalid as those two cells could not be part of the 3 clue and they are not the 1 clue. So we know that both 3 clues of row 19 cannot be on the right and one must be on the left. So R19C2 and R19C3 are black. The rest solves normally.

Very challenging puzzle Tom!

Found to be logically solvable by Gator.

thx for your patience Gator, i worked long & hard on it :)

Liiiiiiiiiked this one verrah much! Thank you, Tom!

thx JoDeen

Another way to solve it:
After line logic, edge logic on the 6 in c20 makes r20c20 white and r14c20 black.

(As per Gator) the 7 in r19 is limited by the 3s in r18. Straight line logic says the 7 could be anywhere from c9 to c20. However, if it is in r9, 10, or 11, a block of four will be forced in r18. This cannot be, so the seven must start no earlier than c12. This makes r19c16-18 black.

Now I did edge logic on the 5 in r20. Again, straight line logic says it could be in c8 to c19. However, if it starts in c8, 9, 10, or 11 it will cause a conflict in r19. Thus limited to c12-19, r20c15-16 must be black.

The rest is line logic.

great solve

thx bugaboo

I went back and started over. I think I had a mistake the first time, because the second time, I was able to do it with not much difficulty.

Really cool puzzle, Tom. (Thanks, Jay, for explaining the meaning.)

Nice!

I had to read Jay's comment to get it...thanks. What's the little h at the bottom?

its a lil n

Cute, very cute. Not sure if this is what you guys do for edge logic, but after I got the top done, I was stuck. So I started putting the 6 black pixels in column 20 in each possible place until I could use color logic and not get an error. Do you mean when I use edge logic I'm supposed to remember what will happen where before I start filling in? I'm sunk.

Edith, read the FAQ on the left, then click on the link for Advanced Puzzle Solving Techniques at the top of that article. Those two pages will be really helpful.

Thanks, Tom. I think that is more or less what I do. :)

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