It’s time to wind up the volume 10 review, with a few highlights behind the review table.
The first one is the very unusual basic trace of IV-12, the homework puzzle of the previous post.
You have the characteristic Extremely Hard stinginess in the bypass, then a near collapse in the 1: list in box marking, with normal box marking completing the collapse. The 3-fills are plentiful and decisive.
Here’s the grid as box marking resumes.
Along with bypass solutions, here is something else an Extremely Hard collection should avoid: a routine basic, and a solution by means of:
a regular 475-wing, rare, but not extremely hard. That’s in Extremely Hard 10 I-3.
The Guide explains when this happens and when it doesn’t.
Then capper in I-3 is a 5-chain skyscraper.
The collapse begins with C5.
Extremely Hard 10 IV-47 is another puzzle embarrassed to be found in an Extremely Hard collection. Advanced fun starts with a remote pair that’s hard to miss.
Next, another regular 251-wing. The grouped 1-chain victim is advanced level hard, but hardly extreme. The knockout blow for IV-47 is a short XY-chain ANL.
And finally, there is Extremely Hard v.10 VI-9, starting with a beautiful spiral, . . .
. . .and moving, Hodoku batting cage style, to a remarkable nice loop, which triggers the collapse inducing 1-wing.
In closing this review of volume 10 of Rebecca Bean’s Extremely Hard Sudoku, I recommend its highest ranking puzzles as an advanced collection, with the possibility of an extreme challenge.
Next week, as part of a progress report on the Sysudoku Guide, checkpoint your solution of Andrew Stuart’s fourth and most challenging example in the WXYZ-Wing page of the ‘Bent’ Sets section of his Strategy Families page. In case you don’t want a peek at his example first, here is the starting grid.