Gamasutra - Games Demystified: Portal

Gamasutra - Games Demystified: Portal: "[In the second in this series of articles which deconstructs a particularly fun or interesting mechanic in a recent, relevant game, Jeremy Alessi pulls apart Valve's Portal and puts it back together again -- to give us a clearer understanding of the compellingly-executed teleportation mechanics central to that game's astoundingly entertaining gameplay.]"