Jigsaw Killer Sudoku
Mar 2nd
I’ve recently been working on refreshing the content for PuzzleMix.com, my play-online puzzle site, and one of the puzzle types I’ve been making is Killer Jigsaw Sudoku, where you not only have the jigsaw-shaped Killer regions but also jigsaw shapes instead of the regular 3×3 Sudoku boxes.
So I thought it would be a good idea to post one of these puzzles here – they can be quite tricky, at least until you get your head around the difference between these and regular Killer!
The rules are simple:
- Place 1 to 9 in each row, column and bold-lined region
- Place numbers in the dashed-line cages that add up to the given total for that cage
- No number can be repeated in a dashed-line cage
Good luck! 
Samurai Odd-Pair Sudoku
Mar 1st
Samurai-2 Odd Pair Sudoku puzzle
One of the brand new puzzles in Sudoku Xtra issue 4 is Odd-Pair Sudoku, which I wrote about last week here on my puzzle blog. As well as some regular 9×9 puzzles I also included a large 5-grid Odd-Pair Samurai puzzle, and to illustrate how the puzzle worked I included a small solved example alongside. A full 5-grid Samurai was too big to fit sensibly in the example box, so I made a 2-grid Samurai version just for that little solution area. So that’s the solution used, but what about the puzzle itself? Well, here it is! (And so if you want to check your solution – yes, it’s printed in Sudoku Xtra issue 4! Page 19, to be precise).
The rules, in case you missed them, are really simple:
- Place 1 to 9 in each row, column and bold-lined 3×3 box of the two 9×9 Sudoku grids
- Every pair of squares with an ‘o’ circle between them must sum to an odd value. (’o’ for odd). So for example you could have “3 o 6″, but not “3 o 5″ (since that would sum to 8, an even number).
This variant is fun because it eliminates lots of possibilities from squares relatively quickly, so you’re left with more deductive logic and less pencil-mark housekeeping.
Good luck!
Sudoku Xtra magazine issue 4
Feb 25th
Issue 4 of Sudoku Xtra magazine is now with us! I really think I might be putting too many puzzles into it, because typing up the list of content just knocked me out with how much is crammed into its 52 large-format pages! Is too much possible? I don’t know, but look at this enormous list:
128 puzzles in total, including several seriously giant ones. Brand new for this issue:
- Samurai Star Killer Sudoku Pro
- Number Link Samurai
- Odd Pair Sudoku
- Samurai Odd Pair Sudoku
- Sudoku Inequality Jigsaw
- Jigsaw Sudoku 6×6 Variety Pack (including toroidal, inequality, X, consecutive and killer)
- Killer Sudoku Pro Jigsaw
- Sudoku 15×15 and Sudoku 18×18
- Killer Sudoku 15×15
- Odd & Even Pair Sudoku
- Killer Sudoku Prime
Regulars from issue 3:
- Hanjie
- Masyu
- Calcudoku (three times as many as in previous issues!)
- Slitherlink
- Consecutive Sudoku
- Hitori
- Samurai Star
- Samurai Star Jigsaw
- Number Link
- Jigsaw Sudoku 8×8, 9×9 and 10×10
- Toroidal Sudoku and Toroidal Inequality
- Kakuro
- Futoshiki
- Killer Sudoku
- Skyscraper
- Skyscraper Sudoku
- Samurai Sudoku
- SSSS: Skyscraper Samurai Star Sudoku
- Sudoku Inequality
- Sudoku Extra Regions
- Jigsaw Sudoku Extra Regions
- Killer Sudoku Jigsaw
- SOS: Samurai Outside Sudoku
- Outside Sudoku
- Sudoku 8×8
- Sudoku 12×12 and 16×16
- Samurai Extra Regions
- Yajilin
- Nurikabe
Adding to that already exhausting list still further are the community puzzles:
- Heyawake
- King’s Journey (also known as Hidato[TM], Numbrix[TM] and many other names)
- Mosaic (Minesweeper picture puzzle)
- As Easy as ABC
- Knight’s Tour
- Shapely Skyscraper
- Isolate
- Klump
And all of this for just £3.99 or $5.99 – it really is fantastic value!
If you’d like to get hold of it just pop on over to the Sudoku Xtra website!
Crazy Calcudoku!
Feb 23rd
Samurai 8-grid Calcudoku puzzle
Here’s probably the largest Calcudoku puzzle you’ve ever seen! It’s made up of 8 underlying 9×9 grids, each of which must have 1 to 9 placed into each row and column, and then on top of this I’ve added the familiar Calcudoku regions.
For each Calcudoku region just place numbers such that the total after applying the stated operation between the numbers in the region is the one given. For example, 7+ could be solved by 3 and 4 (3+4). For subtraction and division start with the largest number in the region, so 1- could also be solved with 3 and 4 (4-3).
Just to make it really clear, there are no 3×3 Sudoku box regions in this puzzle – just the 8 sets of rows and columns.
Good luck!
Sudoku Odd Pairs – a new variant!
Feb 23rd
Now here’s something I can guarantee you won’t have seen before, because I just invented it! Well, I suppose with a world of people creating Sudoku variants it’s possible there’s been something similar before, but I’ve bought a lot of puzzle magazines and books and never come across it, so perhaps I should say I can just about guarantee you won’t have seen it before!
So the puzzle is Sudoku Odd Pairs, and as the name implies it’s all about odd pairs of numbers. Now you may have come across regular odd/even Sudoku before, and to be honest it’s a pretty dull variant (which is why I’ve never made them) – in fact if you for example shade all squares that contain even numbers it just breaks into two separate puzzles that overlap, and if you instead mark just a selection of even (or odd) squares then it’s only interesting until you work out whether the shaded squares are odd or even.
Sudoku Odd Pairs isn’t like that, because instead of marking squares what I’ve done is mark pairs of squares. Some squares have a grey circle between them – you can think of this as an O for Odd. What this means is that the sum of the solution of these two squares is odd. I don’t mark all odd pairs, however, because if you do this you need only one single digit in the entire grid (any of the givens will do) to work out which squares are odd and which even and then you end up with the above boring variant again. So this is important: you can’t infer anything about squares without an O between them – only those with the O between.
It turns out (at least in my opinion!) that this is actually a really fun variant, because you end up with many interesting parts of each puzzle where you realise you can force sets of odds or evens into groups of squares (and not just those with the Os on), which in turn effect the rest of the puzzle. You do to an extent need to make pencil marks when solving, as in Consecutive and many other variants, but the nature of the constraint is such that the number of pencil marks is roughly halved relative to most other variants which (for me at least) makes it far more fun.
I’ve talked about it enough. Try out the puzzle here and let me know what you think!
And if you would like more of these, I’m putting them into Sudoku Xtra issue 4 (out soon!), including a nice Samurai version.
Some new paint
Feb 22nd
I never really liked the old design of the site – it wasn’t lively enough for me. I’ve been idly thinking for quite a while that I should do something about it, and so finally I have.
Everything’s pretty much where it was before, but much shinier. I hope you like the new look!
Sudoku 36×36
Feb 21st
Giant Sudoku puzzles are one of those things that divide people. With 25×25 puzzles some love them, whilst others simply can’t understand why anyone could ever have the patience to do them. But whatever your personal opinion, they remain popular – even Nikoli (the people who named Sudoku ‘Sudoku’) make them regularly, and sometimes include them on special fold-out sections at the back of their books and magazines.
Since they are so divisive I try not to include many of them in Sudoku Xtra magazine (one of each, in fact, plus a 20×20). Therefore I recently created books of both 16×16 and 25×25 puzzles – available pre-printed or for download. However what I’ve never tried making is a 36×36 puzzle – is there anyone, anywhere who would want to do one of these? If so, let me know!
So just for fun, for those who would consider it fun, here’s a 36×36 Sudoku. Just place 1 to 36 into each row, column and 6×6 box. You’ll be relieved to know that no pencil marks are required to solve this puzzle!
Good luck!
Sudoku 15×15
Feb 19th
Something plain but unusual – a Sudoku 15×15. I’m sure these must exist, but it occurred to me I’d never actually seen one. So I made one.
The rules are as you’d expect: place 1 to 9 and A to F into each row, column and 5×3 bold-lined box.
There’s no need to make pencilmarks to solve this – scanning is sufficient.
If you try it out, good luck!
Sudoku 16×16 Volume 1 – Sudoku Xtra Specials
Feb 15th
A book of just 16×16 Sudoku is now available both for download or in pre-printed form from Lulu.com or Amazon.com (with free delivery in some cases).
I’ve had lots of requests for a book like this over the past couple of years, so I hope if you’re one of the people who’ve wanted something like this that the book meets your expectations! All of the puzzles have nice symmetry, and the difficulty level is set such that you won’t need to make lots of fiddly pencil marks in the grid (or indeed any pencil marks at all, if you don’t want to).
It’s printed on large paper (A4 at Lulu, 8″x10″ at Amazon), with just one puzzle per page, so you’re getting the puzzles at a comfortable size for solving. Full solutions are included, and with 50 puzzles it’s going to take you a long time to solve them all!
Please feel free to post any comments here, or head over to Sudoku Xtra and take a browse on the discussion forums – and maybe join in!
Sudoku Xtra Specials: Sudoku 25×25 Volume 1
Feb 5th
I’ve had many, many, many requests over the past years for a book of giant 25×25 Sudoku puzzles, so I have now finally made just such a book available!
Right at the moment it’s only available in printed form, but I’ll have download copies available in the next couple of days – as soon as I’ve added a purchase mechanism to SudokuXtra.com in fact!
I’ve decided that I’m going to make a series of similar books of particular requested puzzles, all of which will be branded as “Sudoku Xtra Specials”. In this way I can stay organised by keeping all of my download/printed content under the ‘Sudoku Xtra’ heading. It means that you’ll always be able to find all of my new content in one place, without searching around my various sites.
This book is probably the nicest collection of 25×25 puzzles you can find, if you’re a fan of such things. Every puzzle has really nice 8-way symmetry – having noticeable patterns in puzzles like this is pretty unusual, and it can help with the solve too. Just as in my magazines, I’ve thought about what’s sensible in a puzzle like this so they can all be solved without needing pencilmarks. How exactly would you go about making A-Y pencilmarks in each individual square anyway?!
If you get hold of it please do let me know any thoughts you have on it. In the same way as for Sudoku Xtra magazine, it’s designed to be printed at home on either an all-together or a page-by-page basis. And if you get a pre-printed version from Lulu or Amazon.com (already complete but waiting on listing now) then it’s on a large A4 (Lulu) or 8″x10″ (Amazon) page, so there’s plenty of room to write in the solutions.
If there are other books of puzzles you’d like to see, please let me know in the comments here or on the Sudoku Xtra forums – feel free to repeat any requests you’ve made before! Next up is 16×16 Sudoku but after that it’s all open. I was thinking of doing Inequality Sudoku third, but what do you think?
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