Here we review as one collection the “extreme” puzzles in Paul Stephens’  two current books, Mastering Sudoku Week by Week and The Sudoku Addict’s Workbook.

In Stephens’ Weeks, puzzles for weeks 26 through 52 are labeled “Extreme”.  By this, Paul means that these puzzles require an advanced technique that he labels “extreme”.  Also, in Addicts, puzzles 121 – 150 are labeled “extreme”.  As an aid to learners of his system, Paul suggests what the solver should find in these” carefully  graded puzzles”.  For the review I selected about one in four puzzles,  three puzzles from Weeks, ending with the last, and seven puzzles from Addicts, including two of the last five.  Of these five, Paul says, “The final ‘fearsome five’ are among the toughest you’ll find anywhere.”

You can conclude from my last few posts that I don’t recommend  Weeks or Addict’s as  guides to solving strategies for sysudokies .  However ,  I do endorse the “extreme” puzzles in these books as challenging enough for my faithful readers.

By now regular readers have seen grading reviews of collections by Tom Sheldon,  Frank Longo,  and KrazyDad.  If this is the first you’ve seen, I suggest a visit to the reviews page first to pick up on the conventions of the very compact review table.  In the review table the puzzles are numbered as they are in the two books.

With the exception of Addicts 142 and 150, the seven Addicts puzzles are less generous with starting clues and box marking clues.  Line marking  gets progressively harder  until, in Addicts 142 and 150, box marking makes line marking easy and unnecessary, respectively.

The bv map is generally well populated, resulting in extensive XY chain removals.  Sue de Coq and APE are rare, as expected.  XYZ wings did get text attention, but not the ER aided variety found in the puzzles.  Among the 10 review puzzles there were four UR removals.  Two appear to be unplanned, contradicting Stephens’ preview hints.

On the X-panel, the collection provided disproportionately little on regular fish.  It may be due to the spoiling of intended regular fish by slink marking, a basic solving technique not anticipated by Stephens.   Finned fish were encountered in the puzzles, but were absent from the texts.

Some interesting coloring experiences were encountered, and these can be translated into Stephens’ less transparent square based “multi-colouring”.

That is as far as the collection goes.  No second tier advanced techniques like AIC and ALS toxic sets are needed.

Next time, I’ll have snapshots of some of the interesting situations encountered in the Stephens review collection.  Let’s  wind up here with the conclusion of Addicts 140.

The ANL found by the ANL test creates a 6-clue in the C box, and this is marked to generate two more clues with a trace of

C6=>(W6m, C2=>Cc5np79=>S6, c2np89)

and to remove two of the 9-candidates.

Going to coloring on the cental bv cells, color traps remove two candidates.  One way to explain the traps is to say that both are false if either blue or green is true.  Another way is to say that, via forcing chains, both candidates see both ends of the short cut slink between the two colors .

The two removals bring a quick collapse, starting

SW3=>(SW9=>SE2=>NE9=>(N9=>(NW9=> .  . . , S9, S7, N8), N7), c4np79=>Sc4np35) .

Next are Extreme snapshots.