You may solve the easy levels by simply eliminating all other possibilities but this is not possible in hard or impossible mode. You start with fewer numbers in the grids and have to think around the corner to make it. Quite a challenge. Portable Sudoku does not require installation and can be stored on an usb stick for instance.

The game is automatically saved when you exit it and it has some modes that make life just a bit easier. Check mode checks the numbers that you have entered thus far. Solve game on the other hand solves the complete game which could be nice if you are stuck and can’t continue on your own. The download is only 400k in size and available for windows.