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Feedback and Questions

I've received a lot of interesting comments and questions from Sudoku fans over the last few years and this page is where I try to answer them. Please feel free to drop me a note on the side of the page or try the Facebook comment box. Or you can email me directly at .

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Any Sudoku you want to publish here for easy loading into the solver - 81 characters, use '.' or '0' for unknowns.

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Many thanks to all the people who have helped improve the solvers and strategies with their feedback!

Sunday 24-Jul-2016

... by: Andrew, England

How are you doing? Thanks for the site.
I'm looking at your solution to a Kenken that I created. The step that I can't understand is as follows:
Killer Innies/Outies
DOG LEG (3): Removing 1/3 from C3
DOG LEG (3): Removing 1/3 from E2

How do you apply the indies/outliers to Kenken with -+/ and x involved? I can only find the reference to Sudoku.

Kind regards

Andrew Stuart writes (30-Jul-2016):

Despite KenKen clues not always having + clues the rows, columns and boxes still have to add up to 21 (in the case of 6x6, 45 in 9x9) and therefore can in principle be decoded using the same technique.

Thursday 21-Jul-2016

... by: David E. Schellenberg, Winnipeg, Manitoba, Canada

Load Sudoku:

Solver makes J2 into an 8 without any good reason.

Andrew Stuart writes (30-Jul-2016):

8 really is the last remaining possible candidate. 8 and 3 are the last two in the row, but 3 is present in A2.

Sunday 17-Jul-2016

... by: Jean, UK

Hi there. your web page is brill by the way. What I want to do is put my own jigsaw suduko in to work with but I'm not sure how to do it. I don't understand the "load 81 characters" bit. Really look forward to your reply. I have a couple of jigsaw Sudoku puzzles that are really hard and are driving me crazy cos I'M STUCK lol.. Many thanks jean

Andrew Stuart writes (30-Jul-2016):

Yes it's been in my job queue for a while now to allow user defined jigsaw shapes. I will try and get it done.

Thursday 14-Jul-2016

... by: John D Traka, Mosinee WI USA

on the website, there's a puzzle for today (7/14- #3861 moderate) and it has two cages with nine cells that total to 45. the killer solver is saying those are illegal cage sizes and clues. just thought you might want to investigate; thanks!

john d traka

Andrew Stuart writes (30-Jul-2016):

Yeah...I regard that as a variant on Killer, my definition insisting on cages with less than 9 cells. Otherwise it could encompass normal Sudoku.

Wednesday 13-Jul-2016

... by: Swagman, USA

Still printing out in bold have to use smaller size still fills the page and its also bold, regular print won't print on just one page. Check everything on my end prints find in other apps.

Andrew Stuart writes (30-Jul-2016):

Do you perhaps have page zoom set to something very high in your browser? There is a reset to normal somewhere in settings. Depends on which browser. [CRTL]+mouse wheel sometimes does it.

Monday 4-Jul-2016

... by: sherie, california

This is very helpful. Can you please remove the black background and make the background white do that we can print it to study?

Andrew Stuart writes (30-Jul-2016):

You need the [print version] which is a link at the top of every documentation page. Also removes the menu, and has a flex-width so most printers can cope.

Saturday 2-Jul-2016

... by: Beekeeper, Denton County, TX

Really neat educational tool. The more I solve the easier it gets. Some are really tough. Great site.

Wednesday 29-Jun-2016

... by: Carl, Northern Ontaro

Andrew, your solver cannot solve some of your diabolical puzzles which I have brought up. Does that mean there is no solution or might they be beyond the skill of the solver?

Andrew Stuart writes (30-Jun-2016):

The solver has been updated since the stock was made. I'm aware that there is now something tiny difference that is causing previously solvable puzzles (and therefore gradable) to become 'unsolvable' and I'm trying to track that down. What was the last puzzle with that problem? Can you remember?

Saturday 28-May-2016

... by: Pieter, Newtown

Hi Andrew,
Happy 11th Birthday to you again for the Solver!

I refer you to a comment in Feedback by Philipp, Germany on Saturday 30-Dec-2006 (2006 page 1). He says "If I try to solve this sudoku there is only found a hidden pair but then there is nothing else... Is it impossible to solve it by logic steps?"

I was surprised the Solver still didn't solve his puzzle even after 9 1/2 years further development, despite brute force finding the solution! I suppose there will always be unsolvables ... it just surprised me. :-)

An Unsolvable for your collection, though you probably already have a record of it!

Also a comment by steve brod, utah on Sunday 31-Dec-2006 ... referring to the 16x16 solver you wrote the year before. I've never seen it. Did/will it ever get done? :-)


Andrew Stuart writes (29-May-2016):

Thanks you for your best wishes! Been so worthwhile and a lot of fun

Not looked at 2006 for a while, thatís for sure. That sudoku reminds me of Escargot, high clue density. I would have liked to be able to offer a solver that solves them all by now, but still a case of chipping away bit by bit.

I can reveal the 16x16, very much an early prototype that hasn't seen any work on it since those days. I've shied away from it since 16x16 isn't a popular puzzle and I never made enough of them to grade the puzzle properly. Also quite a challenge on the UI. But as a bit of fun, here is the link:

Thursday 26-May-2016

... by: Dave, Indianapolis

When I click on a cell of the "Enter Clues" grid box on the left a small box pops up with "PK59A" in it. I'm guessing that's supposed to be suggested entries. However, the suggestions are always "PK59A". Doesn't seem to be relevant to me.

Andrew Stuart writes (27-May-2016):

Thatís weird. What solver? Sudoku vanilla? What OS and browser are you using. Could be some debugging dropping I left behind but I cant reproduce. Certainly not a value suggestion

Saturday 23-Apr-2016

... by: Sean, Omaha

Thanks for this website. You saved my sanity and proved to my wife you don't have to "guess" to solve a legitimate puzzle. Pointing pairs. I won't soon forget it.

Andrew Stuart writes (23-Apr-2016):

Excellent! So glad you found it useful
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