Puzzle Description:

I know it's been done before (including by me), but this time it's a fancy 20x20 :)

#1: Web Paint-By-Number Robot (webpbn) on Jan 2, 2023

Found to be solvable with moderate lookahead by infrapinklizzard.

EL 3 c20 = r5-20 white
LL

Since the 5 in r1 will trigger the 7 in r2 no matter where it's put, the 3 in r1 can only be in [c17-20] meaning r1c18-19 must be blue

LL to finish

I don't seem to have needed any look-ahead

I used edge logic as my "lookahead" logic. Curious how you solved it Lenore. I had to go lookahead after only 3 blue squares. How did you do it?

Repeated edge logic at the bottom gets it. No guessing (lookahead) required.

EL gets this one done!

I used El on the 8 in C1, then easy peasy after that.

Gary - Actually edge logic counts as lookahead!

Fun puzzle, Kristen. I'm not getting the feathered reference...does it describe a fancy script technique?

Ah, yeah, that's probably the confusion. I think people are mistaking "lookahead" with "guessing". If you have to look at more than one line of clues at a time (other than color), then you are "looking ahead" of the logic in a single "line". Edge logic, smile logic, two-way, etc. are all considered "lookahead" (also known as "advanced logic).

Yes, there is a reason that we have coined the word "lookahead". It is separate from "guessing".

Guessing is where you place a pixel without any justification and keep going.

Lookahead is "placing"(without marking) a pixel or set of pixels without justification, and then going ahead in your mind to see if it leads to a contradiction. If it does, then you know that your assumed pixel is incorrect. If it does NOT, then you cannot say anything about that pixel and you must abandon it or you have guessed.

Note that the use of lookahead can only lead to ruling out whatever color you placed in that pixel to start with. It cannot, by definition, prove that the color you guessed is *correct*.

If the number of steps you have to look ahead is only a couple, as in our "advanced" techniques such as edge logic or smile logic, then we label it "moderate lookahead". If it takes much more than that, *but a solution is provided* then we label it "deep lookahead".

If there is no moderate-lookahead solution, and no one has provided a deep-lookahead solution, then it is *according to the procedures of this site* deemed to be "guessing needed".

Note that ALL lookahead is logic-based. Guessing is not lookahead, it is guessing. If you are not 100% sure of the pixel you have marked, you have guessed.

After edge logic on c20 gets r2&3c20, then either r1c20 or r4c20 forces r4c19. LL from there.

iT'S BEEN SO LONG SINCE i HAVE DONE EL. It took me a minute to remember it. Really fun solve, Kristen.

Teresa, I know I said it before, but I am so glad you are back!!

Re: #9, it's a blue J. Get it? With the feathers? And it's fancy?

Re: #13, TERESA!! We were worried about you! Welcome back!

Also, now that I look back at it, it *does* look like a T, but I assure you it was based on a fancy J. :)

Kristen, I'm glad you clarified your thoughts. It really helped me and gave me a lift...today, I am so discombobulated,, "Blue Jay," would probably not have connected with my mind. I love it, thanks!

Blue-J...clever. Thanks for the explanation!

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