I love this version of Sudoku. I have used mostly the Washingtonpost one online, so I am bit partial to that -- however Mario's sudock compares excellently to it. The cosmetics of this version are spartan -- but the emphasis is on the difficulty which can be adjusted infinitely. I found that even given quite a few freebies I had trouble solving, and I usually get the Washingtonpost 5 star puzzles in less than 1/2 hours. So in terms of brain power, this was excellent.

Some things I was not used to -- it is hard to see which numbers are "given" because they no only are the same color, but can also be changed just like all the other numbers. This is a pain in the butt, but it also can work the other way since you can adjust those as well and get a totally different solve to the puzzle. I would either fix this, or use it to create alternative "endings" to be submitted or somethng like that -- It might be fun.

I will look for updates. Thanks for providing a great piece of software.