The last review Sudoku of the Lucky Panda Books 500 Sudoku Puzzles, 480, finishes on message with Sysudoku’s choices of bv mining tools, the XY railway and coloring. If you have time for nothing else, you might try your hand on the line marked grid, before peeking.

This puzzle is suggested as a typical example for choosing lines to mark as the number of unmarked cells increases.

The line marking trace shows that after lines of 3, 4 and 5  unmarked (free) cells are marked, four rows of 6 free cells are selected, over two columns of 6 free cells, and two of 7 free cells.

The box marking trace explains why I’m dropping the “m” (for “marks”). The “t” will remain, to mark aligned and unaccompanied triples that sweep cells in neignboring boxes. Also remaining are outside the list values and special marking symbols, such as Ens3 and SE3t above.

The first advanced move is a good example of finding ANL and nice loops along the XY railway. The railway links candidates in separate bv that see each other.

This railway turns out to house three XY terminals of value 7 for five ANL removals and two of value 6 for one ANL removal.  Then a connecting spur forms a nice loop for three more.

After the follow up

a blue/green cluster, started in the NW box, expands to trap 4r41c.

The follow up expansion of the cluster

wraps blue.

NW5 removes blue 1r2c1. The green collapse is immediate.

This wraps up the Lucky Panda review.  The review table belies the cover claims of being “insanely difficult” or “driving you to the peak of Sudoku mastery”.

On the contrary, the experience you get from these puzzles is limited to the occasional nd easy advanced.

Next is a review of another 500+ collection claiming to be “Extreme”, this one by PencilPress. It isn’t at all extreme, but the book is entertaining for those working on the bypass, so the plan is to checkpoint one review puzzle per weekly post, with some exploration of interest to advanced readers in each post.

The review starts with the bottom right hand puzzle on page 9, and continues with the same position every eighth page, that is 17, 25, . . . The reason for this offbeat pre-selection is that the 500+ puzzles aren’t numbered. Buy the book, and you’ll have time to get ahead of me, and catch violations of bypass protocol, as well as mistakes.

The advanced segment of the next post will be an alternative resolution, without trial,  of Rebecca Bean’s Extremely Hard, v.10, section VI, 24.

The multiple cluster trial solution was posted March 22, 2018. The archive menu on the right gets you there.