Congratulations on making such a powerful program.
I have tested it with 13 puzzles from several sources and find the program fast. If I can solve a puzzle, it takes me 5 to 10 minutes
to do what the program does in 1 second. Also, if I make a mistake that prevents me solving that puzzle. Your program is self-correcting, I wish I could be.
Here is a good one for you
The zeros represent blank cells. I can't fill in one cell using Plan A - slice and dice. Neither can I fill in one cell by Plan Z -
examining the possibilities for each cell. If anyone knows how to start this puzzle by just using a logical brain, I would like to hear from you.
The program solves it but takes longer than the usual standard puzzles - what can you expect when you give it a very very hard puzzle.