Interesting article on Gamasutra: Designing for Motivation This article explains keeping players motivated using a simple PNRC system, thusly named for Player state, Needs, Reward and Challenge. Although a little long in the tooth on the first page, the other four pages are chock full of practical guidelines and examples of where games have both succeeded and failed in meeting this system. It's an interesting concept to keep in mind while designing a game since it's so easy to lose the attention of the player. I've even found it to be applicable to my own project.