Puzzle Description:

#1: Belita (belita) on Feb 10, 2018

Inside circle? Inside out?

I, too, say inside out.

Boy you turn me.

Also, I'm sure some users could explain better, but I'd like to take a stab at a hint. I used moderate lookahead combined with color logic to tell that the blue had to be a circle, or at least circular. In the least, it helped me dot/white out some squares (depending on whether you use dots or pure white squares for blanks). Later, I just had some black squares to fill in at the bottom left corner. I used IEL to figure out that C7R19 had to be dotted/blank. LL solved the rest.

Neat.

Inside out is correct.

when ll/cl runs out (with only eight blue pixels and the letters I N S I & D in black)

el 6 r6 = c6, c15 w
ll/cl finishes the blue

iel 4 r19 - if it were all the way right, it would conflict in r18. So r19c8 is white
ll

at this point, I see no reason why c7r19 must be white. Both r19's 4 and c7's 3 can fit there with no conflict within several moves.

however, with deep lookahead:
if the 4 in r17 were to go all the way right, it would pin the 3 in c7 into one of three places:
> r15-17 - the 2 in r16 would then cause a conflict no matter which way it went, so the 3 cant go here
> r16-18 - the 2 in r18 would be forced right causing a conflict in c8, so the 3 can't go here
> r17-19 - the same as above, so the 3 can't go here, either
= since the 3 can't go in any of those places when the 4 goes all the way right, the 4 cannot go all the way right and r17c8 is white.

ll to finish

Found to be solvable with deep lookahead by infrapinklizzard.

I think there's inside line logic on the blue, but not lookahead or guessing.

This is definitely at the very least moderate lookahead. However, I doubt it. (Anyone is welcome to post a moderate lookahead solution if they can find it.)

What do you call "inside line logic"? Line logic is using only clues from one line at a time -- not using any of the crossing clues.

Here is a page that describes the various advanced techniques we have named on this site. (They are all moderate lookahead.) http://webpbn.com/index.cgi?page=solving.html

Yikes, that was really a challenge. But a great aha! moment at the end.

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