Sudoku Help - Possibility Highlight Options

Here's a page from the extensive help system for SudokuDragon. It is displayed as a help screen when running the program. To get the full picture Download our Sudoku Dragon and see the screen in its full context.

When you are using the automatically displayed possibilities you may need some help in working out which of these actually apply. Sudoku Dragon indicates which ones are allowed/forbidden by highlighting the individual displayed numbers in the grid. You can change this option at any time. Use the 'Possibilities' tab to select which squares and possibilities are to be displayed in this way.

Within the possibilities there may be some that can be quickly shown that are 'forced'. That is one of the possibilities is the only conceivable one allowed. If you would like an explanation as to why the program reckons that this is the only choice you can use the Game hint or Possibilities option to explain what is possible and what is impossible. A sample of what the highlighted possibility will look like is shown in the sample after the name of the rule. A different colour combination is used for the 'only choice' and 'only square' allocation rules.

More complex are the excluded possibilities. The Sudoku rules produce some interesting 'positive' rules (only certain allocations are possible) but also some 'negative' ones (certain allocations are not possible). You can elect to see these excluded possibilities. If you would like an explanation as to why the program reckons that a possibility is excluded then you can use the Possibilities option to explain why it is not possible. A sample of what the highlighted possibility will look like is shown in the sample after the name of the rule. A different colour combination is used for the 'excluded group' (for example naked twin) and 'excluded shared sub-group' exclusion rules.

Tracking the number of possibilities remaining is very useful. If a particular number has only one or two squares remaining then that is the number to try to solve. Similarly if only very few squares are filled in with a number then this may require a new strategy to solve them. Sudoku Dragon uses a special graphical display on the possibility bar to show that all squares for that number have been solved; only one remains; two remain to be solved or none solved; only one solved or only two solved.

Note that if you pause the mouse cursor over the possibility bar the tooltip will show the number of squares filled in.

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