Discuss anything and everything about Sudoku Xtra, from what you think of particular puzzles and would like to see in future issues, through to any that you might want help with. General puzzle discussion is welcome too!

Yes, it can be quite time-consuming to generate large jigsaw puzzles with non-trivial (i.e. not mostly rectangular) jigsaw regions. Making very large samurai jigsaw puzzles in particular doesn't work very well if you do it with entirely random regions. Have you found a quick way to detect this with any given layout, or have you recursively searched for all possible fits and found none? I haveby

Another fun variant along similar lines is when you allow numbers to repeat in a region based on certain rules, the simplest of which is that there must be precisely one number that occurs twice in each bold-lined region (and each other number occurs once). This is sometimes called 'surplus sudoku'. Often to make this work you'll need to have one 'special' region, for example in a 9x9 puzzle you'by

That's a great puzzle and I think constraints like this are good fun. There have been several Sudoku variants that include regions like this (the simplest perhaps is where this constraint is used on all diagonals, including those shorter than 9 long; see also 'isosudoku'), but I don't recall ever seeing it combined with a skyscraper variant before.by

QuoteMathimagics However while effect of zero on the puzzle itself is nil, the effect on the solver is certainly noticeable! All of the stuff you know by heart about row/col sums, minimum/maximum sums has to be re-learned. I'm glad you wrote this! I published a Killer Sudoku puzzle in Sudoku Xtra a few issues back that used 0-8, and I had multiple people contact me (including one posting hby

Hey, what a great idea! I presume that the small letters in the puzzle are actually givens, but you've written them small so that there is plenty of room to write in the actual numbers once you've found them work out. These are more interesting with your skyscraper zero variant than they might be with regular skyscraper, since in the regular puzzle you'd have more of a clue where the "1&by

I've just updated the website so that the Magazines and Books download pages are now much, much easier to browse and read. They're both database-driven which means it will be much easier for me to add new content (e.g. books!) to the site, and also it means I can automatically make new stuff appear on the front page (although I haven't done this yet). I'm also hoping to do some other automatedby

The Samurai Skyscrapers are very hard - there is no shame in not being able to complete these! Or put it this way: Skyscrapers are one of my personal nemeses! I've seen people solve the regular ones in about 30 seconds, on the same puzzles that take me several minutes... Meanwhile, issue 14 is finally available! See the Announcements forum for the full details!by

Sudoku Xtra 14 is now out! It is available for download and all subscribers should have already received their copies via email. It's jam-packed with puzzles, including another bumper Community section, and this issue I've introduced a new puzzle to the magazine: Tapa. The magazine starts with a cover Yajilin Redux that spells out "S X 14" in rotational symmetry, and features theby

Sorry about the spam question... I don't understand why it appears sometimes and why not other times (when logged in), but I don't dare disable it in case the forum gets overrun with spam! You're welcome to post me the sheet if you like?by

QuotesueThe conflicting choices were mainly beween the placing of the 9's and 8's. I opted for a 9 in the 3rd cell so my line 1 reads 129 647 835 and the rest fell into place from there. I keep looking to find an error somewhere but haven't seen it yet. I can guarantee that there is only one, single solution to this puzzle, and it can be reached with straightforward step-by-step logical deductby

Hi Sue, I do all the subscriptions manually so you're perfectly safe renewing at any issue number and just emailing me to say what number you'd like it to start from (I'd probably work it out anyway), but this site is definitely overdue an update to the ordering/subscribing process! Yes, I'll email you when issue 14 is out - it's actually almost complete, but I just haven't quite got round to fby

It's possible I've used the wrong name somewhere, but usually odd/even sudoku refers to a puzzle where odd/even squares are shaded to distinguish them - essentially two separate puzzles that overlap, if all such squares are marked. The puzzles I think you mean are Odd Pair Sudoku, with markers between certain squares. (I know you know this, but I'm just clarifying for anyone else reading!) Iby

Well done on the Samurai Star. They're a lot quicker once you spot how each triple of 3 numbers repeats every third block of three numbers. I'm particularly pleased you enjoyed the heyawakes - I tried to pick a different theme for each of the smaller puzzles which would help with solving the larger one at the front. I was pleased with the 8765 numbering too.by

I've just had the time to take another look at the Tiger in the Woods puzzles and here's my honest opinion: they're not that hard. I thought they were all really enjoyable puzzles that just needed a different mindset to solve. I solved each one in about a minute or so, using no complex logic at all. The secret is to solve them very differently to a regular logic puzzle. Instead of starting witby

Finally, the big cover Heyawake. Here's a clue: start with the touching 0 and 5s right smack in the centre of the puzzle. You can place quite a bit here right away, and then the puzzle solution ripples out from the centre both anticlockwise curving out and clockwise curving out, finishing where they meet somewhere on the lower left.by

And here's clue for the bottom puzzle on page 13. Look at the corner '4's. There is only ONE possible solution to each of these 4 areas. If you place these that should get you going. You can also use similar 'zip' logic around the edges of the left-hand 5 region to mark some squares as definitely empty.by

The Heyawakes are pretty tough, I agree. I had great fun making these! Here is a clue to get you going with the 8765 one on page 13. Look at that 7. It has to be a 'zip' pattern running one of either two ways. Either way it goes, however, the adjacent squares on each side in rows 1 to 6 must all be empty. Now look at the 6. The top 4 rows can only have 2 shaded squares now, so the bottoby

Sorry for the delay on the Lulu edition - I've dropped everything else to get three puzzle books finished by the end of the month. Sorry!!! (only one or two copies of each Lulu edition are bought each month)by

Trivia, but not trivial. Isn't the search for perfect numbers one of the oldest problems in mathematics?by

I've updated the PDF, should anyone wish to fetch a version which correctly describes what these numbers are. (Note that this has no effect on how the puzzle actually solves, since it was just an item of trivia). Thanks very much to Jim for spotting this!by

Of course you're right. I half-edited the description of the numbers to fit on one line but didn't finish doing so - I will update the PDF. As you say, the numbers given are 'p' such that 2p-1 × (2p - 1) is a perfect number.by

I think the path has to start either in row 4 or the bottom three squares of column 5 - if it doesn't then it can't visit R4C5, since there are no places it can turn to reach this square. I don't see how you eliminate column 5 as a possibility right at the start, but for the purpose of the next step of the walk through it doesn't matter because you have proven where the start isn't (i.e. anywhereby

Well I can't speak for anyone else but I certainly wasn't offended! Like I said, it's brilliant to see people discussing the puzzles!by

PS And I thoroughly recommend Deb's excellent work-through - it's awesome!by

Some puzzles arouse strong emotions, and Deb's example of Numberlink is spot on. Some people can't bear them, and I must admit that when I first tried Numberlink I thought they were ridiculous. However with experience I learnt to visualise them much more easily, and my Numberlink intuition grew to the point where they are now one of my absolute favourite puzzles of all. Whether that will happeby

Sudoku Xtra 13 is now available! Final checks are complete and it's now ready for download! Pre-printed versions will follow soon. It opens with a huge front page Heyawake puzzle and then continues with an expansive selection of 138 varied puzzles, as well as yet another packed Community Puzzles section featuring such favourites as the ever-popular Labyrinth. Other gems in this issue includeby

I based the instructions for this puzzle (Tiger in the Woods) on those given in the 2009 LMI (Indian) puzzle championships, where this rule about finishing only on what would be a turn square wasn't stated. It does at least make the puzzle a bit easier when you add that additional restriction in! I do apologise for this confusion, and I should have made sure I'd checked the instructions with tby

I haven't tried the challenger yet I must admit! I'll email you now.by

Okay, the PDF online is updated if anyone would like to re-download it.by

Ah, that's a shame - both David and I checked they'd been copied from the originals correctly but we must both have missed that column, probably because it was at the end. I'll fix the download PDF. Just to be clear, Nathan's original puzzle he sent was correct - the mistake was when the print-ready graphic was prepared.by

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