## A Bridge Over Insane 485

Insane v.4 b.8 n.5, the eighth puzzle of a review of the KrazyDad Insane collection on www.krazydad.com,  had little left after Sysudoku basic solving.  XY chain ANL and a coloring bridge, supported by a cloud of bi-value cells, finishes it quickly.  This post also notes two personal landmarks, the second anniversary of this blog, and my upcoming 7th marathon.

There wasn’t much left to look through in the search for SdC, APE, and XYZ-wings.  The bv map produced a long XY-chain with these blue and green ANL removals.

I did an X-panel to avoid overlooking something obvious, and went on to exploit the cloud of slinks with some coloring.

Two well populated clusters emerged,with a common number  5. This made it easy to spot a bridging connection of colors in r6:

not(blue and orange)

=> green or red.

Then the blue 5-candidate in r9c7 blurted out “I see red and green!” and was promptly booted off the grid, along with all the rest of the blue clan .

As you would expect, the installation of green clues decided all of the remaining cells.

You can start basic solving on the last KrazyDad Insane puzzle of this review, Insane v.4, b.10, n.5, or Insane 4X5.

Here is how it went on Insane 495. Box marking was routine.  Line marking was hard, and left a tough grid crowded with candidates.  One break was a naked triple generating a complementary one in the SouthWest box.

The effort is evident when you look at the line marked grid below.

I’m going to make an example of two Sue de Coq chutes that are very hard to verify.  Maybe you can find these needles in this haystack.

My first post was 9/29/11.

I explained there my  purpose of developing material for a book on human engineered, systematic methods of solving hard Sudoku puzzles.

I never expected to be refining these methods two years later, but here I am.  Posts are now weekly, but the earliest posts were more frequent,  as I tried to establish the systematic approach in basic solving methods.

Early on, good  examples were in short supply.  Computer solved examples  don’t tell you much about efficient human solving.  Once I had covered enough advanced methods, I started reviewing puzzle collections and Sudoku authors, and this has brought many excellent examples, and added insights that I hope to convey in the book.

When will I get around to it?  My blog readers will know, because I will be blogging about it. My editing on the book will be accompanied by revisions of some earlier posts, for new readers to benefit from my two years of human solving experience. For right now, I have added the bv maps, XYZ wings and XY-chains to the Solving Templates page of this blog.

If you can, come to the Akron Marathon next Saturday, the 28th. Look for me in the 5-hour pack at the start, and somewhere around  the 5 hour pack leader at the finish. Or later.  Look for “John”.  Mention the blog or Sysudoku.  It will give me a large charge and a big boost.