Su-Doku Puzzles are the latest craze in games but there isn't a computer graphic in sight.
Su Doku began its gentle attack on the nation last year, and versions can now be found in four national newspapers. Addicts are as obsessed as 1980s teenagers fixated on the Rubik's cube.
So what's the big deal about these little rows of boxes on a page?
An unscientific poll brought two types of reaction to the hybrid Japanese name Su Doku. While some bemused colleagues had never heard of it, others rather uncomfortably lined up to confess their addiction to the game.
For anyone who doesn't know, it's a puzzle found in newspapers, books and online. A simple-looking grid of nine rows by nine, split into nine boxes, each containing nine squares, it looks like just another numbers game.
But, say Su Doku experts, the difference is it can be played using logic alone, so maths phobics read on.
To be pure Su Doku each of the unique puzzles - which come in varying levels of difficulty - must have only one solution. The aim? To fill in the grid so that every row, every column, and every box contains the digits one to nine.
This simple game has spawned a complex industry, according to the man who brought Su Doku to UK newspapers. Plans are afoot to add the game to mobile phones, and a board game and television show could soon leap on the bandwagon.
The internet is awash with chat about Su Doku and programers are tapping away to find the best system for solving the puzzles.
'Engrossed'
"I know if I've got a busy day ahead I won't even look at a difficult one, because once you are hooked into it you have to keep going," says Peter Levell, who keeps his playing to about three times a week.
"The easy ones I can now do in about 15 minutes, but more difficult ones can take a couple of hours and I just don't have the time," he adds from his home in Guildford, Surrey.
The 64-year-old vicar denies being "addicted" but his son Tim says during dinner at his house recently his father and brother "ignored everyone else while they did a "fiendish"-level Su Doku".
"So much so that, at gone 11pm, I had to say I was going to bed, because I was tired and they were so engrossed they showed no sign of leaving."
Bernard Stay, 71, from St Albans in Hertfordshire, has had a more extreme reaction.
"I would really like my life before Su Doku back!" he pleaded recently on a website.
"I never thought I had an addictive personality, but Su Doku is definitely bad for me. If I don't complete a puzzle before noon I get suicidally depressed for the rest of the day and even lose sleep fretting on what I've missed."
The man behind the
website - who is credited with bringing the game to the UK - is Wayne Gould, a retired judge from New Zealand who lives in Hong Kong.
'Spread the word'
He is pleased with the global growth of the game, to which he contributed by taking it from a puzzle book he bought in Tokyo in 1997 and spending six years - "on and off" - writing a computer program that produces new Su Dokus on the spot.
He currently provides them free to newspapers in 11 countries from the United States to Slovakia, and will soon add a publication in the former Soviet state of Georgia to the list. He's not making big profits off the big craze, saying his income from it is "pin money."
It was his collaboration with the Times that brought the game to the UK in November 2004, and given that his first aim was to "spread the word" about Su Doku, he's tickled but not hugely surprised at how it has engaged the population.
Mr Gould is particularly pleased that the government-produced Teachers magazine recommended last month that Su Doku be used as brain exercises in classrooms.
"It's good for getting the children to explain and discuss the logic," says consultant editor, and part time secondary teacher, Steve McCormack, "for dealing with numbers and for organisational skills."
But it's the spin-offs, like computer program sales, books and soon-to-be-launched downloadable Su Doku for phones, that have taken Mr Gould aback.
After the newspaper brought it to the UK, the obsession with the game reached such a level over winter that by the time the Telegraph launched its own "sudoku" - different spellings in different newspapers - its provider was swamped with e-mails.
Michael Mepham, a veteran puzzle producer, dusted off programs he had for similar brainteasers to come up with a Su Doku one. Since the Telegraph published the first puzzle on 24 February - a Sunday sudoku launches this weekend - he has received 60,000 emails.
He admits an early glitch created a puzzle that had more than one solution and "by golly did I get some mail" about it, he says.
But generally the feedback has been positive, curious and overwhelming, he says.
"I've never seen anything in the puzzle industry that's caused such a fuss. It's just one of those things that catches on."
