An XY Playground in Classic 72

James Forest’s Classic 72 delivers two rare birds, then gets tripped up by a Y-wing.

The bypass threatens to take over, but leaves  an XY playground.




The line marked grid gives all of the Sysudoku Basic results.

Two fill strings of one value is a bit unusual.

The generous bv field predicts a productive XY railway system.




But first we look for UR, SdC, APE, and other methods not requiring maps and panels.

Here we have a classic indeed, an ALS toxic pair. The 3 value is contested, but 8r5c9 sees both groups of 8 that would be locked in by the winner.


Significantly, a 4-value Bent Almost Restricted n-Set, a BARN, can be superimposed around the ALS pair. Only the 8 values are bent. The removal is not as significant.

The significant removal is 6r1c4. It’s a 3-node XY-chain, adding  an NEr1 boxline removal and a naked triple in c4.

Collapse is immediate.






Next is Classic 96 (left) and 120. Both are solved in Basic.  Have your versions ready.




The Guide pages Sysudoku Basic, and Begin With the Bypass have been updated. If you’ve been putting off a serious evaluation, now is a good time.

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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