Puzzle Description:

#1: Tom O'Connell (sensei69) on Nov 2, 2013 [SPOILER]

cute pony tail

I'm (a little) surprised at the 1 3/4 difficulty rating on this one. This is actually harder than that if solved with logic rather than symmetry.

The most-used advanced techniques seem to only give deep-lookahead solutions. Eg. two-way logic on the 1 in c9 will make c7r7 black after a few steps.

However, a much overlooked technique can give us moderate lookahead. Summing is rarely used mostly because it is hard to find applications for it outside of blotted puzzles.

We can use it here, though. If we sum the whole of the pixels yet to be placed, there are eight in each direction. That doesn't really help other than confirming we can add.

However, notice that the left 3 in r7, the left 1 in r8 and the left 3 in r11 all must be in the left half. The right clues in each of those rows must be in the right half. Only the 2 in r9 could be in one or the other, or both.

So let's sum the left half's vertical clues. That's (unsurprisingly) four.

And the left half's horizontal clues? Let's do the definites first: one more for the left 3 in r7, the left 1 in r8, and one more for the left 3 in r11. That's three definites for the left.

Four vertically minus three horizontally means that one (and only one) of the 2 in r9 must be in the left half. So r9c10 must be black, and line logic finishes it.

Found to be solvable with moderate lookahead by infrapinklizzard.

It doesn't seem as if Mary is checking her puzzles to see if they are logically solvable. Neither does she seem to be solving her own puzzles before posting them. She should do both being careful when she solves her puzzles to use just the clues and not fill in squares from memory. She has some cute ideas but so far most are not making very good puzzles.

AWE!

Found to be solvable with moderate lookahead by infrapinklizzard.

Here's a second puzzle that has un-solvabled itself.

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