As background for some of the techniques used in F2P, there's a classic reference on behavioral psychology applied to games from 2001, way before the whole F2P

As background for some of the techniques used in F2P, there's a classic reference on behavioral psychology applied to games from 2001, way before the whole F2P phenomenon: http://www.gamasutra.com/view/feature/3085/behavioral_game_design.php http://www.gamasutra.com/view/feature/3085/behavioral_game_d...