Kiwi computer whizz is one out of the box

Wayne Gould

Wayne Gould, a New Zealander who practised law for 13 years in Matamata before heading to Hong Kong, found the puzzles in a bookshop while killing time in Tokyo's Ginza district.

In his retirement, the mechanics of the Sudoku grid of columns, rows, and boxes strewn with seemingly random numbers mingled with Gould's passion for computer programming.

The challenge of coming up with a program to solve and generate a vast number of the puzzles took six years.

But eventually he came up with a commercially viable system and - as our main story on this page shows - his puzzles have taken Britain by storm. And from Monday, Herald Sudoku devotees will get more opportunities to stretch their brains when Sudoku moves from appearing five days a week to six days, graduating from easy and medium to hard.

On public holidays there will be very hard versions, a bonus for real addicts. From tomorrow the Herald on Sunday will carry a hard Sudoku each week.

The standard Sudoku formation is a grid of nine boxes, three deep and three high. Each box is divided into nine squares. Once solved, every number from 1 to 9 appears once in each vertical column, horizontal row, and box.

Each puzzle has only one right answer.

Try pencilling in the number you think is correct in case you need to test another combination.