You can either play 'blind', or with all possible unallocated digits shown in the empty cells. You can also get the program to do all the tedious work - but you decide which of the routines is applied and in what order. There is a unique scoring system for each grid.
You may build your own new grid, (or copy one from elsewhere), and you can ask the program to compile a new random grid. All grids can be saved to a database - the program comes with a library of over a hundred sample grids.
You can not only print a grid, but also Worksheets for playing on paper. (At present the program doesn't support USB printers).
The program was written under MS-DOS, but installs like a standard Windows application, including a Desktop icon. You may download a free trial version from this website which you may play with - but you can't write your own grids, nor compile new ones unless you register. It will run under most versions of Windows, but not anything before Windows 95.
Registering your copy (which will cost you £6.50) will give you full access, and disclose the logic of all routines. Once you have become familiar with the rules, you will find even more enjoyment from playing the game on paper.