
Finned Mutant Swordfish 

A Finned Mutant Swordfish is three primary units that contain a candidate only in three secondary units, except for one (or more than one if they share a tertiary unit). Please refer to Mutant Swordfish and Finned Swordfish. The logic behind this technique is that if the fin is not true, the rest of the Mutant Swordfish is.
Consider the example on this page. The candidate is 4 and the primary units are the topmiddle box, row 5, and the bottomright box. All the 4's in these units have been highlighted in blue. The secondary units are columns 4, 6, and 9. All the 4's in these primary units can be found within these secondary units, except for one, the lowermost 4, which is the fin. If the fin is not true, then the mutant swordfish is true causing the elimination of all the other 4's in columns 4, 6, and 9. If the fin IS true, then it eliminates all other 4's in the bottom row. Either way, the two 4's highlighted in green can be eliminated.
Note as usual that not all fins must be only one cell. Sometimes a fin can extend to several cells that share the same tertiary unit. For instance, if in the example on this page the bottomright box had another 4 in the bottom row (directly to the left or right of the current fin) it would still be an extension of the same fin. The logic would then be as follows. If none of the cells in the fin is true, the Mutant Swordfish is true. Otherwise, if any of the fin cells is true, we can still make the eliminations hightlighted in green.
Sudoku Snake gives Finned Mutant Swordfish a skill value of 2000.






