Hi there,
I am working on a way to measure difficulty of grids. I am currently using SUDOKUjm (on www.sudokujm.com) since it gives stats as to how many different actions have been used to sove a grid. Several "difficult" grids turn out to be solved with only one or two actions (Clear singles / clear doubles), but the real tough ones need 4, 5 or 6 actions to be solved.
Can anyone direct me to a source of perceived super-tough grids? I would like to corroleate this perceived difficulty with stats provided with the software. If this works, this will enable the software to be better at producing grids of the desired difficulty level.
thx,
jm