It is pretty cool, if I say so myself. In addition to doing Sudoku without symbols, just using colored blocks, there are some bells and whistles. There is a facility for hints
You can set breakpoints to try a branch and return easily to that point. You can load and save puzzles from text files. The app contains a number of puzzles of different degrees of difficulty. I can put a copy of the app on Dropbox once I figure out the new public link system, if there is any interest.