A little counting game where you place stones onto a board such that the sum of all surrounding stones is equal to the value of the stone you placed.
Click on a square to place a stone there, right click to undo a move, and press
N or P to play different boards.
This game is based on the one shown in the Numberphile video "Stones on an Infinite Chessboard".
To build the game, open it up in Godot 3 and export the project.