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.




Posted in Advanced Solving, Basic Solving Procedures, Puzzle Reviews | Tagged , , , , , | Leave a comment

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.


Posted in Basic Solving Procedures, Puzzle Reviews | Tagged , | Leave a comment

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.

Posted in Advanced Solving, Basic Solving Procedures, Puzzle Reviews | Tagged , , , , | Leave a comment

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.

Posted in Advanced Solving, Puzzle Reviews | Tagged , , , , , | Leave a comment

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



Posted in Advanced Solving, Puzzle Reviews | Tagged , , , | Leave a comment

LuckyPanda 96 and 144

This post has a bypass trace to the solution of 96 in Lucky Panda 504 Sudoku Puzzles, and a basic trace and immediate coloring wrap for 144. The review will continue with single puzzles. It’s not mentioned in the text, but all the review puzzles start with 30 givens, an untypically high number.

LuckyPanda 96 is resolved in the bypass. The trace reveals a large contribution of 3-fills. The bypass comes close to drying up, before the rapid collapse.

Here is the grid as the trace ends with a solution assured. The lower case singles are effects not yet taken as causes.





The LuckyPanda 144 basic trace is more normal, taking matters into advanced.




The naked triple in line marking adds three bv.










Lucky Panda review puzzles consistently have a large number of bv cells. This makes XY-chains and coloring consistently effective. In 144 there is also the typically large number of slinks to support early coloring.

A blue/green cluster starting in the NE box spreads over the grid and wraps blue as two blue 5-candidates see each other. With green installed, the collapse is immediate.






Taken for what it is, the LuckyPanda collection is good Sudoku entertainment. The overblown labels of “extremely hard” and “insanely difficult” sell short what Sudoku has to offer. LuckyPanda Sudoku is recommended for those equipped in  Sudoku basic and exploring early advanced techniques.

Next is Lucky Panda 192.


Posted in Advanced Solving, Basic Solving Procedures, Puzzle Reviews | Tagged , , , , | Leave a comment

Lucky Panda Books Extremely Hard 48

LPB 48, the first review puzzle of Lucky Panda Books 504 Sudoku Puzzles, features an interesting hidden dublex and many unresolved 3-fills with fill strings trimmed by line slinks. The easy line marking closes with a DIY unique rectangle. A large bv field enables a coloring finish, with or without an XY ANL and a follow up UR.

It’s easy to dismiss the this large size paperback, especially when you see the back cover, and the two pages of explanations, basic tips and techniques. The collection is nothing like “Extremely Hard”, or “Insanely Difficult”, as claimed , and working all 504 will not bring you to a state of peak Sudoku mastery. Review puzzles 48, 96, . . . 480 are entertaining at the basic and early Advanced levels, and have instructive moments.

The layout is different: four puzzles to a page and answers to the eight puzzles of a spread at the bottom of the next spread. The review puzzles are on the bottom right corner of every sixth spread.

The Basic trace of  LPB 48 is promising. A host of 3-fills, many unresolved, stretch the bypass trace across the page, to a hidden dublex on value 9? And a breakout in the line marking close.

The bypassed grid reveals the story of the hidden dublex.

Taking out the SE9, you see that the S9 is confined to rows r78, a double line exclusion forcing SE9 into r9, while N9 keeps NE9 in c8.

Want to be a master of Sysudoku Basic?

Read traces.

Now a look at the Line marked grid, to pick up on something I just realized about 3-fills and line marking. In box marking, you can shorten the 3-fill strings by removing any value closed in the line.  Note how row fill strings of 3-fills are shortened by this action.


Also, Advance overlaps Basic with a variation of UR Type 1, as 4r5c4 removes both 4 and 6 from r78c4.

Both XY chains and coloring are favored by the bv forest. Coloring goes all the way from here, but an interesting side trail is XY ANL, with follow up




that removes 4’s and enables


another unique rectangle, Type 1.










Coloring resolves the near BUG and wraps blue for the collapse of LuckyPanda 48.









Next in the review, LuckyPanda 96 to the right,  is a bypass casualty.

The bypass trace will be here next week, with a solution of number 3, Lucky Panda 144 at the left.



Posted in Advanced Solving, Puzzle Reviews | Tagged , , , , | Leave a comment