Great for all skill levels

1. Allows for easy annotation of possibilities for those who need to do this
2. Allows for easy update of possibilities
3. Optional settings allows to set auto updates or manual updates and several things to choose from to make the game work the way you want it to function
4. For people who are learning, there is a hint feature that points you to a block, row or column and gives you a chance to figure it out. If you cant, it provides a further hint until the answer is revealed. What I like best about this feature, is that it explains the rationale so that you may learn a new solving technique.

kpakov about ⋆Sudoku+