Su Doku began its gentle attack on nation last year, and versions can now be found in four national newspapers. Addicts are as obsessed as 1980s teenagers fixated on Rubik's cube.
So what's big deal about these little rows of boxes on a page?
An unscientific poll brought two types of reaction to hybrid Japanese name Su Doku. While some bemused colleagues had never heard of it, others rather uncomfortably lined up to confess their addiction to 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, difference is it can be played using logic alone, so maths phobics read on.
To be pure Su Doku each of unique puzzles - which come in varying levels of difficulty - must have only one solution. The aim? To fill in grid so that every row, every column, and every box contains digits one to nine.
This simple game has spawned a complex industry, according to man who brought Su Doku to UK newspapers. Plans are afoot to add game to mobile phones, and a board game and television show could soon leap on bandwagon.
The internet is awash with chat about Su Doku and programers are tapping away to find best system for solving puzzles.
"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 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 rest of day and even lose sleep fretting on what I've missed."
The man behind website - who is credited with bringing game to UK - is Wayne Gould, a retired judge from New Zealand who lives in Hong Kong.
He is pleased with global growth of 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 spot.
He currently provides them free to newspapers in 11 countries from United States to Slovakia, and will soon add a publication in former Soviet state of Georgia to list. He's not making big profits off big craze, saying his income from it is "pin money."