# 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. 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...**
## Tuesday 10-Aug-2021

## ... by: brent hudson, United Kingdom

Firstly, what a brilliant programme! I have used it a lot over the last 2 years as I've tried to improve my own solving skills. It has helped me improve a lot.

However, on this board I have been able to solve a puzzle that the solver cannot, and I would expect it to be able to. I am wondering why it cannot.

Here's the board:

There is a Killer Sudoku board I would like you to look at

Click on this link:

https://www.sudokuwiki.org/killersudoku.htm?bd=121112211121133441112213122132112111332312322111311321221213311133221121114411121,300622000012002100000000001600040000000025003200191400000600000013000000000000130000151200210000000000000022130000210000000000180500000027001000000008000000000000

When it gets stuck, cells G6, H6, J5, and J6 sum to 13 (by summing columns 7, 8, and 9 and looking at the spill over). 13 in 4 cells in the same block has to contain 1. This means that J4 has to be 2 (the solver gets stuck with J4 being only 1 or 2).

If I set J4 to 2, the solver then solves the puzzle.

Why doesn't the solver see that J4 has to be 2?

I ask for two reasons:

1. The solver seems to solve much harder situations than this one.

2. If you do decide to update the solver again, maybe there's a piece of logic you could insert?

Again - thanks for doing the solver; it's a great tool!

Brent

## Sunday 8-Aug-2021

## ... by: Kelly, Belgium

I have a really difficult (Double) Jigsaw Sudoku I want help solving with. The grid of the jigsaw is not one of your grids. How can i make my own grid and use your solver?

Thank you so much in advance!

Kind regards,

Kelly

## Monday 5-Jul-2021

## ... by: Jurgen, Belgium

I'm trying to enter a puzzle in the small grid on the left but when I type 8 it gets replaced with a 9 ....

I was trying something to get ipad keyboards to map letters to numbers and I can't work out why it's effecting normal keyboard usage (I can't duplicate) so I've reversed the changes

Tell me if it's back to normal.

## Monday 14-Jun-2021

## ... by: Steven, USA

In a simple colouring step, all of the 4s on diagonal 1 are taken away and there's no blue colored 4s, only yellow

LOAD PUZZLE

Assuming it is Sudoku X my offline solver says this puzzle has no solutions

I ran through it until it found a contradiction and could not see the simple colouring step you describe although a few simple colourings were used.

I found a javascript bug when the 3D Medusa was used. That stopped Take Step button from working. Nice to fix that

## Thursday 10-Jun-2021

## ... by: Philip Trueman, England

Load today's (10th June '21) Killer into the solver and turn off all optional techniques. Look at the cage that sums to 30. Mark the two cells in column 4 as a 5/9 naked pair. Hit Solve. The 5/9 elimination does not propagate to every remaining cell.

Bug report most appreciated

## Thursday 27-May-2021

## ... by: Christopher Eastwood, Washington State, US

Done now, have a go

Thanks!

## Wednesday 14-Apr-2021

## ... by: David, UK

Load Sudoku: CLICK TO LOADThis solve comes up with

XY-Chain

length=9, chain ends: A6 and E2

This proves 5 is the solution at one end of the chain or the other

-5[A6]+4[A6]-4[B6]+9[B6]-9[B4]+6[B4]-6[B7]+2[B7]-2[H7]+5[H7]-5[H5]+9[H5]-9[D5]+5[D5]-5[E4]+8[E4]-8[E2]+5[E2]

5 taken off A2

Can you explain how in the red route (5 in A6) that it can assert that 5 is in E4.

Sorry if I am missing something!

Fabulous site - thank you.

All the connecting cells have two values.

A 5 in A6 will cascade all the other cells to reach E2 forcing it to be 8.

A 5 in E2 will cascade all the other cells to reach A6 forcing it to be 4.

There are only two ways the chain can be settled, both imply a 5 in A6 or E2. Therefore no 5 in A2

## Wednesday 14-Apr-2021

## ... by: Andreas, Germany

Found no useful alternatives on WWW.

## Sunday 11-Apr-2021

## ... by: ATechGuy, United States

I was so saddened to hear your site had been hacked. As an IT MSP, we see it all the time and it's such negative energy. Your Apr 11 update made my day that you were able to recover your site. I so love your solver--it has taught me a lot about the puzzle. Sudoku is part of my life and I try to "wake up" my brain every morning by doing a few puzzles. I'm sure it also helped keep my mother's brain more active in her last years.

All the best,

-Ken

Always appreciate a thumbs up from visitors

## Saturday 10-Apr-2021

## ... by: Conway, England

## Friday 2-Apr-2021

## ... by: Douglas Boffey, England

I know this is rather an esoteric technique, and not easy to explain.