@inproceedings{DiGRA-2013-Karhulahti,
	author        = "Veli-Matti Karhulahti",
	booktitle     = "{Proceedings of the Seventh DiGRA International Conference: DeFragging Game Studies}",
	ee            = "http://www.digra.org/digital-library/publications/puzzle-is-not-a-game-basic-structures-of-challenge/",
	publisher     = "{Digital Games Research Association}",
	title         = "{Puzzle Is Not a Game! Basic Structures of Challenge}",
	year          = 2013,
}