Fancy yourself as a Sudoku whizz? Can you complete the tasks faster than all your friends? Well, now comes the ultimate test - the world's most difficult puzzle.
Finnish mathematician Arto Inkala spent three months designing a Sudoku grid with only one solution.
Inkala has warned any potential challengers only the quickest and brightest minds would be able to solve it.
Sudoku has become a daily fixture in many people's lives since becoming popular in the last 10 years.
It is a number-placement puzzle game, and the objective is to fill a 9×9 grid with digits so that each column, each row, and each of the nine 3×3 sub-grids that compose the grid contains all of the digits from 1 to 9.
Mr Inkala claims his monster puzzle, hosted by www.efamol.com, is a whopping 11 on the difficulty rating.
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