Another 'semi-addict' here, ffb,
and I would be interested to know how the designer knows which and how many squares to empty to make a particular 'grade' of puzzle. I find a combination of a Suduko and a cryptic crossword an excellent antidote to 'dead brain' (although there are some who would say....
)
No doubt one of our clever clogs will have a link to a writing programme or perhaps even written one!