Two small points from a lurker:
(1) Although I have not read Clark's paper, I noticed through the comments that followed that not even once was the cultural element mentioned.
Let me be more specific. When designing educational games we need to consider that these are culturally specific, and what we in the so-called western world understand as a game, Asian students, for example, are likely to perceive differently.
(2) Including the "artistic" and "post-modern" in (educational) games is also subject to cultural differences. My Japanese students had more problems than my Australian students in understanding how metaphors and metonomies work.