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. I'm also directing Str8ts feedback here. Please feel free to drop me a note on the side of the page. Or you can email me directly at andrew@str8ts.com.
Post a Comment or Question here...
Friday 7-Nov-2025
... by: Philip, United Kingdom
Friday's Killer doesn't solve in the solver!
Andrew Stuart writes:
True! But it does now. Seems there was an old bit of code in the last patch which cause the innie/outie to blank a cell. Tested it now and it does the correct eliminations. Also fixed the [Grader] button which wasn't working while logged out.
Friday 7-Nov-2025
... by: TenPeter, USA
To Ayumu and Davin - You both are absolutely correct. I had erroneously interpreted the description in the Bird Exocet document to imply two cases for the cover-houses 1) orthogonal to the cover lines or 2) 1 parallel and 1 orthogonal. That is not the case as you both observed. Thank you for the correction.
Tuesday 28-Oct-2025
... by: Susan, United States
why can we not see the solutions for the other levels in the daily puzzles? only the level that initially loads up.
Andrew Stuart writes:
Good point. Added solution pickers for all four grades for the Daily Sudoku, Daily Jigsaw Sudoku, Daily Sudoku X and Daily Kakuro
Monday 27-Oct-2025
... by: Hawkeye, US
The Jigsaw Sudoku print function is not printing the puzzle.
Andrew Stuart writes:
Thanks Hawkeye! Try now
Sunday 26-Oct-2025
... by: Sid, France
Hi Andrew, Working on the nice example of XY-Chain appearing in the Daily Sudoku of 10/22, I noticed that while symbol 2 is actually highlighted in green or red at the chain ends, in the solved grid, the solution is symbol 2 at both ends. I can assume that this is possible because of the weak links, but I still can't figure out exactly why ? Is there some more to say to explain this ? For example, does the length of the chain have something to do with this ? Are there examples of chains having same ends and different lengths ? Many thanks and the best. Sid
Andrew Stuart writes:
Good question. The reason is that the chain is reversible but I can only display one direction. So one end will be green and the other red. But the chains can also be reversed. This is a property of such chains.
Saturday 25-Oct-2025
... by: Doll Hellmut, Germany
Hi, the "print" page of the Killer Solver shows only the column`'s numbers and the row's letters. Ctrl +f5 does not work. Can you solve this problem?
Andrew Stuart writes:
Fixed. Very sorry about that. A simple typo bug
Friday 24-Oct-2025
... by: Karwan N, Sweden
Hi.
I want to suggest that the highlighting function of the solver primarily uses high-contrast colors (red & green for instance) no matter which number is highlighted. For instance, 6:s & 7:s are very hard to spot against the white background and the 2:s and 4:s are the easiest.
Andrew Stuart writes:
Good suggestion I will do some testing. I would prefer to have a colour theme for each number as it is used on more than just candidate highlighting, eg link colours as well. But I can do a high contrast version as a selectable option.
Tuesday 21-Oct-2025
... by: Rick, Hong Kong
Hi just want to know how to import/create the custom shape in "Killer Jigsaw Solver". I can create the cages, but cannot the shape. I notice there's custom one to create or import, but failed.
So how should I create it?
Andrew Stuart writes:
Click on the blue button Step 2. I have to separate the two parts of the creation process. Send me a link with the puzzle afterwards, interested to see one I didn't make. Use "Email this board"
Monday 20-Oct-2025
... by: bill, United States
WHY DO I GET THE RESPONSE "reset_yes_no: no row called RUR1"
Andrew Stuart writes:
I split off Unique Rectangles type 1 and put it earlier in the list, must be a month ago. Sounds like you don’t have the latest page. Talking about /Sudoku.htm? Does it say version 2.43.2? Can you press [CRTL]+[F5] to refresh
Send me the puzzle you are working on in case its something else. Use "Email/Export"
Thursday 16-Oct-2025
... by: Rafael, Spain
Hello,
I've been enjoying your solver and your many lessons on the techniques.
I took up sudoku a few months ago and I sit comfortably at the diabolical level now, doing the level 4 sudoku of the day whenever I can.
However, I've noticed that I could not solve some of the last few daily puzzles, and when I gave up and used the "solve path" option, I saw that it required X-Cycles with ALS, listed as diabolical. Is that considered diabolical considering ALS are listed as an Extreme level technique? In my view, combining any AIC (including X-Cycles) with other techniques such as ALS or UR increases the difficulty by a lot.
It's just a silly question, but I hope you can share your insight.
Rafael
Andrew Stuart writes:
Very glad you have been enjoying the puzzle and find the site useful I think you are right. ALS/UR and other exotic links are a bit too much for diabolical grade. I’ll keep grouped-cells inside as they are relatively easy to understand. I’m still tweaking the heuristics for the Daily puzzles so I can do something to flag those puzzles away.
Friday 7-Nov-2025
... by: Philip, United Kingdom
Friday 7-Nov-2025
... by: TenPeter, USA
Tuesday 28-Oct-2025
... by: Susan, United States
Monday 27-Oct-2025
... by: Hawkeye, US
Sunday 26-Oct-2025
... by: Sid, France
Working on the nice example of XY-Chain appearing in the Daily Sudoku of 10/22, I noticed that while symbol 2 is actually highlighted in green or red at the chain ends, in the solved grid, the solution is symbol 2 at both ends.
I can assume that this is possible because of the weak links, but I still can't figure out exactly why ? Is there some more to say to explain this ? For example, does the length of the chain have something to do with this ? Are there examples of chains having same ends and different lengths ?
Many thanks and the best.
Sid
Saturday 25-Oct-2025
... by: Doll Hellmut, Germany
Friday 24-Oct-2025
... by: Karwan N, Sweden
I want to suggest that the highlighting function of the solver primarily uses high-contrast colors (red & green for instance) no matter which number is highlighted. For instance, 6:s & 7:s are very hard to spot against the white background and the 2:s and 4:s are the easiest.
Tuesday 21-Oct-2025
... by: Rick, Hong Kong
So how should I create it?
Monday 20-Oct-2025
... by: bill, United States
Send me the puzzle you are working on in case its something else. Use "Email/Export"
Thursday 16-Oct-2025
... by: Rafael, Spain
I've been enjoying your solver and your many lessons on the techniques.
I took up sudoku a few months ago and I sit comfortably at the diabolical level now, doing the level 4 sudoku of the day whenever I can.
However, I've noticed that I could not solve some of the last few daily puzzles, and when I gave up and used the "solve path" option, I saw that it required X-Cycles with ALS, listed as diabolical. Is that considered diabolical considering ALS are listed as an Extreme level technique? In my view, combining any AIC (including X-Cycles) with other techniques such as ALS or UR increases the difficulty by a lot.
It's just a silly question, but I hope you can share your insight.
Rafael
I think you are right. ALS/UR and other exotic links are a bit too much for diabolical grade. I’ll keep grouped-cells inside as they are relatively easy to understand. I’m still tweaking the heuristics for the Daily puzzles so I can do something to flag those puzzles away.