Puzzle Description:

#1: Michael Frank (mfrank) on Nov 27, 2011

logically solvable, extended edge logic

agree

I solved it using a kind of summing logic.

The first half can be solved using line and color logic.
Then edge logic on the 2 in r11. If it goes in c1-2, then both r13c1-2 must be both white - impossible. If it goes anywhere from c3-c9, then r13c1-2 must be both black - also impossible. So the 2 in r11 must be in c2-3.
Then line logic to approximately 3/4 done.

Now we are left with what is, to an experienced solver, obviously a zig-zag. As zig-zag logic is looked down upon here, I looked hard to find another way to solve this section. The fact that it is L shaped rather than square seemed to give an avenue. So I tried summing.

Look at the cut-off square of c6-9 and r11-14. The across clues in that must fit completely in that square add up to seven. Now look at the down clues for those columns. The clues that are left in those columns add up to eight. Note that if you take even one of those clues away, it will only add up to six -- not enough to fill the necessary across clues.

So all the vertical clues in c6-9 must be in r11-14, at least in part. And since the vertical clues add up to eight rather than seven, one of those clues (as yet undetermined) must then extend out into r15. Therefore, all the spaces in c6-9 *not in* r11-15 (ie the rectangle c6-9,r16-20) must be white.

The rest solves with line logic.

Fun solve, no guessing.

Is that a cigarette? Good message, Mandi.

i also used summing
no guessing

Found to be solvable with moderate lookahead by infrapinklizzard.

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