Here is an article about the psychological factors of fun which could easily be applied to games.
Make sure you also check out the Gamasutra article entitled..."How to Prototype a Game in Under 7 Days:
Tips and Tricks from 4 Grad Students Who Made Over 50 Games in 1 Semester"
Also worth looking at is the Experimental Gameplay site who are also running a competition.
Thanks to Lief, for pointing these article and links out.
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