The goal of the game is to assemble the picture from pieces. Each picture is divided into pieces which are shuffled. You need to get each piece back to its original position. You accomplish that by swapping pieces (exchanging their positions). You have a limited number of swappings for each picture. The game is over when you complete 3 images, and for each one you get the points. If you have a hard time playing this, you can look at the images directory and see what the final picture looks like.
This needs SDL libraries to run. Start via Menu->Fun->Scalar, or by entering scalar in a console.
N.B. To reduce the size somewhat, I deleted quite a few jpegs from /usr/share/scalar/images directory. But if you wanted to create a particular theme for your children, just add whatever images to this directory. The developer mentions that the program will display .jpg, .gif, .bmp or .png formats.