This game is addictive. I started with the basic game until I got the hang of it, then started progressing through the levels. As an extra challenge, I try to play the game without adding the number guesses from the right side. Quite a game -- keeps your brain active! Only thing missing is greying out the numbers that have been completed, so you know not to choose them again and can see which ones you have left.
Brn2act1 about Stress Free Sudoku Game Book!