A bit of a lighter topic today: What is fun?

This seems like a simple question that would be tempting to hand-wave away as a "Well you know..." but the more I think about it the less cut and dry it seems.

Some prompts to get you thinking

• What are the merits and purposes of fun?
• What makes something fun? Though different people find different things fun, is there a common thread that makes those things fun?
• Is it easier for some kinds of people to have fun than others? What kinds of situations lend themselves to fun experiences, which make them difficult?
• Are there ways for people who have forgotten how to have fun to "get back in touch with fun?"
• Do you think you have enough fun? Too much?
• How much fun is the right, or a good amount?