For my site I use a backtracker to find a large number of single solution puzzles (rather fast). Those are used as a test base for my "human" solver (pretty slo

For my site I use a backtracker to find a large number of single solution puzzles (rather fast). Those are used as a test base for my "human" solver (pretty slow), which are used for scoring and difficulty levels. I find that it's a nice balance.