Use 3D chains Click on any candidate in the board. The solver will set that candidate as true and turn false all the candidates it can see in the row, column and box. It will then look at all those in turn and follow every inference, ON, OFF, ON, OFF until it can go no further. A network of chains will be built up that could help you solve a difficult point in the puzzle.

'Use 3D chains' means to follow the chains within a cell. The 'third' dimension of the candidate spread.

Use the [SHIFT]+(click) on another candidate to add another set of chains to the board. Otherwise the previous chain will be cleared. If you click the same candidate it will change from true to false and the links will be tested again with that inference. All chains will only explore un-chained candidates, ie they will not join up.

Quick Rules:

Rows and columns are divided into compartments of white squares. Use single numbers to complete a straight for each compartment. A straight is a set of numbers with no gaps and in any order. No single number can repeat in any row or column. Clues in black cells remove that number as an option in that row and column, and are not part of any straight

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