Deep Blue plays chess by rapidly playing advance moves before making a decision, or gets on television by using tuned search. Is this play? Where is the randomness? At Microsoft, the researchers are looking for the nature of play, and for instance, they found it with the Kinect device.
Now the article : Coherent Inference on Optimal Play in Game Trees . defines a crucial property of games!
A crucial property of games that humans use is that the tree has structure: Winning positions are not randomly distributed among the tree's leaves, but clustered.
Here is a state diagram (which you thought that you would never use outside of college, wrong:
If you like articles with a bunch of references to Bayesian Best-First Tree Search, then this is the article for you!