detuned radio

Sunday, 22 August 2021

Puzzle 358: Masyu

So I don't think this is really as smooth and polished so as to live up to Nikoli standards, but there are a couple of flashes of something here and there to keep you interested, dearest reader. Enjoy!

#358 Masyu – rated 6/10 [hard]

All puzzles © Tom Collyer 2009-21.

Saturday, 21 August 2021

Puzzle 357: Sudoku

I'm going to be posting a few Nikoli style puzzles over the next few days. I was about to say that there probably won't be any Sudoku, but that's not entirely true. As a bit of a preview, there will probably be a few Renban Groups that I'll post, mainly because I've seen too many examples where the groups are presented as lines, rather than shaded regions, and it's annoyed me past a critical point.

Anyhow, puzzles like these I guess aren't as common as they used to be. Nothing too flash here. Enjoy!

#357 Sudoku – rated 3/10 [Easy]

All puzzles © Tom Collyer 2009-21.

Tuesday, 17 August 2021

Maki Kaji

I saw in the news today that Nikoli president Maki Kaji has passed away at the age of 69.

I had the chance to meet him at the 2010 world sudoku championships, hosted that year in Philadelphia, USA. Always fond of games and gambling - Nikoli the puzzle company takes its name from Nikoli the racehorse - he hosted a couple of rounds of the Nikoli derby in which I was lucky enough to finish to second, winning a tenugui which I still have with me today.

(Thanks - in advance! - to Przemysław Dębiak for the photo)

Kaji was known as the “godfather of sudoku,” following his role in the worldwide explosion of its popularity in 2004.

I am tickled to see an example of a Masyu puzzle included on the BBC website (and also how much better designed it used to be!). But I come under the category of a puzzle fanatic. I think part of his puzzling greatness is reflected in this quote:

"The secret to inventing a good puzzle," he said, "is to make the rules simple and easy for everyone, including beginners.

"You have to be able to make both easy and difficult puzzles using the same rules.

"Between 200 and 300 people help to complete a new puzzle. It has to be something that children, old people and everyone in between can enjoy, to be really good."

Rest in peace.

Wednesday, 28 July 2021

Puzzle Projects

First a quick update: I haven't written here for a little while, which feels a bit personally disappointing. I suppose part of it reflects my continuing malaise within the puzzle community. As I've previously said, it used to be a place where I thought I fit in, and increasingly I am made to feel as if I do not. The best way I can describe this is that any enthusiasm I have for the puzzle community has been blunted by expediency, apathy and lethargy.

About this time last year I outlined that I'd like to try and work on a bunch of different puzzle projects as a way of trying to get back into the swing of things. In some ways it was going to be part of my own recovery, but for a number of reasons none of them really happened. The main thing to say is that I haven't forgotten about them, and I would like to try and make them happen.

Recently I have been thinking about what a week-long online global festival of puzzles might look like. And yes, I have been corresponding privately with some relevant people before you ask, dearest reader. But I'd also like to share the sorts of things I would hypothetically like to see.

Portrait of a flying fish

If, like me dearest reader, you are interested in sudoku solving techniques, then perhaps this is an interesting link to a youtube video.

https://www.youtube.com/watch?v=n2No8hU2OwI

If you found that video interesting, then perhaps this is an interesting picture. [Someone going by the pseudonym shye is responsible for this puzzle, and it even has a name. Imagine that, dearest reader: a sudoku with a name! Rather grandly, this one is called "Valtari"]

If you found that picture interesting, then perhaps these are some interesting words.

Add rows 1, 3, 5, 7, 9 together with box 5 (in blue, with double weights in R5C4 and R5C6).
Subtract Columns 3, 5, 7 (in red).
The blue cells, considered with multiplicity, have the same contents as the red cells plus 3 extra copies of the digits 1-9.
In the double-weighted blue cells, the only possibilities are 2, 3 and 4.
There are already exactly two each of 2, 3 and 4 appearing as given digits in the single-weighted blue cells.
This means that whichever two of the three digits ends up in the double-weighted blue cells will end up bring the multiplicity of both of those digits up to 4 within the blue cells.
This means that the two empty red cells have the same contents as the two empty double-weighted blue cells.
It also means that those two digits cannot appear again in any other blue cell.
More on this to come I'm sure, following this good work by Philip Newman: https://docs.google.com/document/d/1Y7m2tTUDmUTj3BZ0w5viNuQlaiBVv9kmYksSLrm_XLE/edit

UPDATE: as far as I can tell, there is no need to add Box 5 to the equation here - this makes the intersections slightly simpler (no need for double-weights any more) - but it does make it harder to identify where you are supposed to be looking.

If you didn't find that interesting, then I'll leave you with some whimsical musings. I always thought that an obscure and difficult sudoku solving technique going by the name Exocet was named for a powerful missile that could bust open the hardest of puzzles. Cela a plus de sens en français.