Game of 15 is my childhood game. We used to play it by drawing boards on the ground. The idea behind the game is to be able to fill all the board entries with numbers from 0 to 9, such that the numbers in each row, each colum as well as each diagonal sum up to 15. You are not allowed any duplicates.
When you are done entering the numbers, click done, and an interactive window will pop up, let you know of the status of the game. After you have hit Done, you cannot go back and change the results. You can quit the game at any time, and you can always try again until you get the game right.
To play the game, download and install python and make sure to install the tkinter library.
Enjoy.