The rules here are really very simple!

It's a basic Sudoku with 1 to 9 appearing in every row, column and each of the nine blocks, although not diagonally (no large 'X'). All numbers that are higher than their abutting non-diagonal cell neighbours in the same block are in the pink cells. All numbers that are lower than their abutting (non-diagonal) cell neighbours in each block are in the blue cells. (The colour relationships do not apply between adjacent blocks!!)

That's it! Definitely enough to get any self-respecting hard-core Sudoku fanatic started with a combination of some logical thinking and standard Sudoku techniques.

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