writes "The open-source Frogatto is now available for free on Linux, Mac, & Windows. A paid version is available for the iPhone. Their website describes the making of the game, their development of Frogatto Markup Language (FML) for describing game data, and their development of the Frogatto Formula Language (FFL) for calculations within FML. The terms of the open source are similiar to Penumbra Overture's.
The game itself is good too."Link to Original Source