The objective of the game is to fill 4x4 square with digits from 1 to 4) so that each column and each row of the big square as well as each of the smaller 2×2 squares contains all of the digits from 1 to 4.

The grid is partially completed and solution is usually unique. You may play on the screen, you can play after printing the picture on the sheet of paper or you can do both.

While playing on the screen the computer helps you by not allowing you to enter wrong digits.

For each good entry you get one positive point and for wrong entry negative one. Only positive points are shown. However, to have a score above zero you must first erase all your previously made negative points. Enjoy!