PencilPress Bottom Right 17 and Moito III-4

The review of PencilPress 500+ Sudoku Extreme Puzzles continues with bottom right, page 17.  Along with that, we return with Sudokuwiki to Moito Road to Mastery III-4, for an alternative solution without a trial.

There is nothing extreme about PencilPress br 17. The value 4 is completely placed immediately, and the S box is filled before a plunging collapse leaves many effects in reserve, but never needed as causes. That counters any claim of being “extreme”.


Moving on to Moito III-47, the basic trace was described as routine in the original post, and a basic trace wasn’t given. You can read it by lifting the givens from this grid showing the naked triple and naked pair in line marking.

Before my party got started, Sudokuwiki uncovered two hidden unique rectangles I missed. The r45c37 rectangle is a Type 1, with two slinks from the corner opposite the bv. 2r5c3 cannot stay, because the removal of 3r5c3 both adjacent corners forces 3, making a reversible rectangle with a second solution. The r12c68 rectangle is a Type 2, slinked across two boxes. Figure out why 4r1c7 must go.

The hidden UR removals are indecisive, and were carried along in the original post.

My first finds, an XY-chain extended by a grouped 4-chain, and 9-chain ANL, boxline and naked triple it enables, were skipped by Sudokuwiki’s going directly to AIC building, with this AIC confirming ANL. Such a creature can be spotted by starting a boomerang from a bv cell.


Follow up marking


includes the naked triple at left.


Then the long XY ANL below triggers the collapse of Moito III-47, starting with:

The color trial is avoided.














Next post, it’s PencilPress Extreme 25, offering a challenging bypass.

Beginning also is an update on the collection of the review of an early “tells all”, which led me to the conclusion that tracing is a necessity.






In that first collection review, the full results for each review puzzle were not published. It soon became the Sysudoku custom to do that, so this update will follow suit for Sheldon’s Master Class. Here is the starting grid for Master Class 30.



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PencilPress Bottom Right 9 and Bean VI-24

PencilPress  500+ Sudoku Extreme Puzzles rates in Sysudoku as basic level, with most of the preselected puzzle on the bottom right corner of pages 9, 16, . . ., being solved in the bypass. In each of the posts verifying this, an advanced topic is also included. This time it’s an alternative solution, without trial, of Rebecca Bean Extremely Hard, section VI, # 24.

Any trace of a solution in the bypass is going to look complicated, but the most moves are simple. Then, as you read the trace by filling the grid, some moves are not. The value of reading a trace is that the reason for the move forms in your own head. Always formulate the reason there before you update the grid. It’s profitable to think also of why the current move was spotted. What change in the grid prompted it?  Sysudoku basic traces follow a protocol. You don’t have to know what it is, but after reading a few traces, you’ll know it anyway.

Here is a bypass trace for bottom right 9:

It starts with the short 5-chain ANL found before coloring. But that blinded me to the 2-chain ANL running alongside.








The elimination sets up two slinks for a grouped skyscraper ANL.





The coloring trial is still available, but Sudokuwiki goes for AIC building, and finds


this confirming ANL.  You or I might be on a boomerang search, but  arrive at a slink into the starting 8 instead of a wink into  2 or 5. That’s a bonus for looking.






The new clue S8 is decisive:

For next time, you can bypass your way through PencilPress bottom right, page 17,




then see if you need to read my trace.

Advanced readers get another go at III-47 from Moito’s Road to Mastery, which was finished with a coloring trial in the post of 1/02/18.





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Lucky Panda 480 Ends the Review

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.




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Lucky Panda 432 Displays a Reversed Boxline

Lucky Panda 432 offers a clear example of a less encountered type of boxline, on the way to becoming a Sysudoku Basic casualty.

grid showing reversed boxlineIn line marking, the newly formed naked pair 13 removes 3r2c4, leaving two aligned 3’s in the North box. One of these must be N3, so the remainder of c6 can have no 3’s. Sysudoku labels this interaction of box and line a boxline.

A reversed form of boxline would occur if 3r8c6 were removed instead, leaving no 3’s in  c6 except the two in the N box. This would require the 3 of c6 to come from r12c6, removing 3r2c4.

basic traceThe details are all there in the basic trace.

Next is the conclusion of the Lucky Panda review, with 480.


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Three Lucky Pandas

This post is a quick report on Lucky Panda Books 288, 336 and 384, with solutions similar to the five covered in the review.

In 288, the bypass starts well on a 3-fill, but dries up fast.


Line marking naked triple in Lucky Panda 288A grid shot of the naked triple in line marking.









ANL and hidden unique rectangleThe full line marking is shown  here, with a hidden unique rectangle and the decisive XY ANL. The UR is plays no role in the collapse.







after collapseThe next review puzzle, Lucky Panda 336, is finished in the bypass. Here is the grid with givens, and bypass clues and pencil marks,


as the trace below is concluded.


bypass trace

basic traceAlso on the quickie list is Lucky Panda 384, which recovers from a near collapse in the bypass.







multiple XY ANLIt delivers this convincing example of multiple almost nice loops along an XY railway. Pairs of ANL terminals are marked by rounded squares of different colors, with victims of correspondingly colored diamonds. Needless to say, collapse is immediate.


Next post continues the Lucky Panda Sudoku review with 432.

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Lucky Panda 240 Rides Nice Loop Coloring

The candidates of a nice loop form a coloring cluster. This review puzzle from the Lucky Panda Sudoku review illustrates a decisive nice loop coloring. Two hidden UR 2 show up as well.

After a productive bypass and box marking,





a naked triple is confirmed on the last line marked row.

Then in the bv scan, a hidden unique rectangle. If r1c7 is 4, r1c8 is 1, and r8c8 is 4. The 1-slink then forces 1 in r8c7 for at least a double solution.




In the bv map, XY chains house two almost nice loops, one leaving a hidden single in r9. The railway also includes an XY nice loop having no direct victims. But Nice loops generate coloring clusters. This cluster is extended by slinks.  The 5r8c6 elimination turns 5r8c4 blue and traps 5r2c4.

After a follow up of E3, N24 and N15,

a second hidden unique rectangle. This time the forcing slink is a 2-slink.

Then, an ANL recycling part of the nice loop to remove 5r1c9 to create an aligned triple boxline.






As E48 expands the cluster, a skyscraper 1-chain wraps green

The blue collapse is immediate. You can trace the skyscraper back to the first coloring, to see if it is decisive, without the later removals..

Next post skims through the next three Lucky Panda review puzzles: 288, 336, and 384. If you are trying Lucky Panda review puzzles ahead, you probably already have your copy. Otherwise, you can pull the givens out of the grids of the next post.

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Lucky Panda 192

This post details the basics and the easy solution of the fourth puzzle of the Lucky Panda Sudoku review, “insanely difficult” 192.  It’s not with a bv map.

The bypass starts with a 3-fill and immediately resolves two. Then slink marking is confined to the middle boxes.








Columns dominate in line marking, which is aided by two hidden singles.







Did you spot anything on the line marked grid?










Going directly to the bv map, two XY railway segments lead to removals.

Which diagram would you prefer for constructing XY chains: the universal keypad grid, the Sysudoku line marked grid, or the bv map? Be honest, now.



Of course you do have to reference the full grid for the candidate victims. The longer ANL eliminates 8r9c9, creating another bv. The decisive blow is a reverse boxline, with the 2r8c6 removal activating  box slink S2m to trigger a collapse.




Next week it’s all about LuckyPanda 240



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