You should ensure there is only one solution before attempting an analysis. (see checking)
The puzzles are classified according to the strategems a human solver would have to use to arrive at a solution.
- easy
- just sole candidate and sole possibility
- medium
- as above plus row and column fragments and ngroups and npossibles of two cells
- hard
- as above plus larger ngroups and npossibles
- very hard
- x-wing, swordfish, conjugate pair chains
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- impossible?
- cannot be solved by the above means, nor by this program acting in 'human' mode