MXQ Adv. Sudoku

Re-Engineered Grids

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Extremely difficult grids are not easy to find. I only encountered 18 grids. Since I wanted to have an endless supply of grids to play with, I experimented with transformations until I had the possibility of 1M+ extremely difficult grids -- obviously many would be uninteresting or repetitive schematically, but there is plenty of room for imagination.


Extremely difficult grids all have 2 empty rows & 2 empty columns. The following grids represent: a butterfly, a happy face, a fountain & a double oval.

ReEng1 ReEng1 ReEng1 ReEng1