A Coloring Tidal Wave Drowns Sufi 37

Here, Brian Challenger’s Super Fiendish 37 makes it to advanced, but with the bi-value field   inviting multi-cluster coloring, a systematically easy solving technique. There are some X-panel fruits to harvest first in the order of battle, before coloring closes the book with a snap.

A Sysudoku review reports how puzzles behave in Basic, the gathering of clues and strong links. In this case, there was some thinning of the candidate cloud in the bypass, and a large contingent of box slinks preceding a naked triple closing line marking.


Here is the line filled grid with fill strings attached.  The naked triple adds two bv.

Some bv are due to local shortages of cells for unplaced candidates. Bi-value cells are the grey areas corresponding to the black and white of clues.


From the bv scan, the first sufi advanced move is this hidden unique rectangle, type 1.  If 3r5c8 is true, then 7 is forced in adjacent corners. Values 3 and 7 can then be interchanged in the corners without affecting any cells outside the rectangle. That means that the whatever solution is derived can be duplicated with these interchanged values.

Next, from the X-panel, an 8-chain ANL brings another bv.










A tentative blue green cluster stalls, but finishing the X-panels brings a swordfish. There’s only one victim, but the removal gets a box/line removal and another bv.





The second, red/orange cluster is pervasive, and a collapse begins with coloring traps. 9r6c3, 4t7c8, 3r9c1 and 4r9c9 see both colors. Cell r9c1  declares that red and blue are not both true, which means that green or orange or both are.




The departures of 3r9c1 or 3r8c7 here merges blue with orange and red with green. And the 1r9c8 trap colors 1r9c3 orange, leaving red in command and wrapping blue in r9c1. Suddenly it’s over. Ever see a solution in color?




Next time, it’s Super Fiendish 47 and 57, both basic.




About Sudent

I'm John Welch, a retired engineering professor, father of 3 wonderful daughters and granddad to 7 fabulous grandchildren. Sudoku analysis and illustration is a great hobby and a healthy mental challenge.
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