Struggling to solve today's sudoku? Is your tried and tested method hitting a brick wall and you feel like you are going around in circles? New research might make you feel a bit better: you might not necessarily be stuck... perhaps you are just in a patch of transient chaos on your way to the solution.

Get on a commuter train these days and you can virtually see people's brains crunching away at filling the numbers from 1 to 9 into a square grid. As the Sudoku craze shows no sign of slowing, Hardeep Aiden investigates its relatives and predecessors.