Among the crucial elements of flow are “a challenging activity that requires skill” and “clear goals and feedback.” So for a game this means that the player knows what they need to do (or could do) and their possibilities as that time are matched to their skill level. Then when the task is complete, they get a reward that clearly communicates their awesomeness and validates their input as a player.
Both of these elements involve rules in some way. As they say, design is about constraints.
I recently encountered a task that involved rules and these flow-conducive elements. In my historical linguistics class I had the following homework assignment.
Please answer any three of the questions, in writing, in no more than a few sentences for each answer. In selecting which questions to answer,you
must follow these constraints:
a. At least one of the questions you answer must be numbered in double digits
b. The total value of the questions you answer, arrived at by adding up the number assigned to each question, must be at least 21.
This assignment struck me as not only very clear and thorough instructions (leave it to a historical linguist) but also as having parameters that added a more flow-oriented dimension to it, making it a bit of a game. Needless to say, it made the assignment fun, but it also added a pleasantly unexpected dimension of excitement. The number-adding component gave a secondary goal to the whole thing, another thing for my brain to work on in the in-between and in the back of my mind while doing the assignment. Something about it just multiplied its interestingness.
I think education should employ this way more often. And games can take note that the addition of a simple mechanic is sometimes enough to make a game more thrilling and engaging.