Answer: shaping
Explanation: The game described above is an example of shaping also known as behavior-shaping which is a type of behavior modification technique (a variant of operant conditioning) in which a behavior is taught by differentially reinforcing successive approximations to the target behavior. In other words, successive approximations to the desired behavior is rewarded. Here, a subject is not waited upon to exhibit a desired behavior, but is rewarded when it exhibits any behavior leading to the desired behavior.