Sudoku has implementation issues.

[Anthony-Handwerker]

The two I've noticed are:
A) Advanced Deduction throws an exception upon being clicked.
B) The case rule always claims to be incorrectly applied.

[Bram28]

There is a lot not right about the current Sudoku rules:

"Forced by Deduction" -> terrible name, since all rules are deductive. Instead, this should be renamed to something like "Only Number" or "Last Number" (for a specific cell)

"Forced by Elimination" -> also a bad name: many rules are based on elimination. This should be renamed to something like "Only spot" or "Last Spot" (for a specific number in some specific row/column/black)

"Advanced Deduction" -> I have no idea what this rule even does. And if it is too advanced, it should probably just be deleted.

There is a presentation for Sudoku in the misc/Rules folder: someone needs to develop those.

[saltzl]

I've started re-writing the rules to match the presentation. Also, I agree, we should get rid of Advanced Deduction.