It's time for more game studies goodness. This one comes from Jesper Juul, a Danish scholar who studied and then taught at the IT University, Copenhagen.
In his article "Swap Adjacent Gems to Make Sets of Three," Juul conducts a history of matching tile games, attempting to create a genealogy of the form. The image above is the family tree he presents as a part of the analysis.
In addition to the inherent value of studying the development of a genre, Juul's paper also had practical application. He used it as a kind of design inspiration when he created his own casual game, High Seas - The Family Fortune, which is a matching tile game with physics and a few other twists.
Juul is also the author of Half-Real: Video Games between Real Rules and Fictional Worlds, published in 2005 by the MIT Press.