Progression is fun. Creating is fun. Earning the respect of your peers is fun. Playing in a well-matched game is fun. Fun is one of those subjective words that is only known through experience. We know when something was or wasn’t fun. Fuzzy Wuzzy was a fun one. Wasn’t he?
What is the nature of fun? How do we “have” it? Is it related to happiness? Is it a byproduct of an activity or a goal? Is it meaningful? Am I a robot? Fun is so central to being human that it is hard to see. From your perspective, fun is natural.
Fun is the using your imagination to play a game. We pretend that we are something else. The surfer rises above the wave. The painter is coated in layers of color. The baker adds the perfect frosting lettering. In the process of doing the thing we become the action and that feeling of flow is fun.