The first thing that came to mind was Tag games. I haven't made it through all the other entries yet, so I'm curious to see if others go there too. I like +Graham Charles
's ball game idea.
So the way the game gets distributed is through the passing along of two or three rules. Like a playground game where it is passed along orally through each successive class. They are rules for creating your game, and the GC entry would be one iteration of the game.
In the game, you're playing a group of people who have developed wild talents. Magical abilities that have suddently come upon them, disrupting their normal daily lives. The talents are almost impossible to control at first, with more control developing over time. People can absorb the powers. They can be transferred and shared through touch. This changes the way people with the powers interact with each other and the rest of their lives.
The first rule would tell you how to create powers. For example, say powers in this world are born of elements. To give a power, create an encounter with an awesome entity of nature that blesses or curses the character. Pick an aspect of that power in the world that the character can now affect, and a gesture they make when they do so. Until they learn control, the effects will be wild and uncontrollable.
The second rule would tell you how to create areas of play at which different types of interactions and role play would happen. For example, if you're playing outside, some large wide-open area would be a place where flight and conflict happen. This would be played out through tag games. Another area could be a place of Listening. A chair is placed with two others nearby. Anyone can sit in the central chair and close their eyes. When two other people have taken the other chairs, someone knocks three times and the Listener can ask a question. The others answer, speaking as ancient spirits that inhabit the space. #gamechef