Some Britons have been a little distracted of late. Pen in hand, brow furrowed, Hazel Warren has been so engrossed that she forgot to put the dinner on. Others have been late to pick up the kids from school, feed the dog, or start the day.
The culprit? A simple Japanese numbers puzzle called Sudoku that is gripping Britain. Newspapers have fallen over each other to feature it. National championships are promised. A Sudoku book has become an instant bestseller. Logic has not been this fashionable since the Rubik's Cube.
"They took over my life," says Ms. Warren of Rochdale, northwest England. "Since I also have a job, I had to really restrict myself to only doing the Saturday one.
"The beauty of Sudoku is its simplicity while at the same time challenging one's powers of logical thinking," she adds.
Sudoku, which means "single number" in Japanese, is essentially a simple logic problem with layers of hidden complexity that can draw the solver in to the point of obsession. A grid nine squares by nine is presented in which all the integers from 1 to 9 must appear in every row, every column and every 3-by-3 box. So far, so good.
Some numbers are given as initial clues. Then, by process of deduction, sometimes resorting to quite intense logical assumptions, the solver can slowly begin to work out what goes where.
"It's the sort of puzzle that you can do everywhere," enthuses Michael Mepham, who sets puzzles for The Daily Telegraph. Since he started out in February, he has received tens of thousands of e-mails and his website has attracted more than 250,000 hits.