Fun on the whole is a pretty amorphous concept and being reasonable about it is tricky, however there are some routes of enquiry.

My personal understanding of fun comes from the experience of programming gameplay mechanics (such as character control, AI and minigames) and through designing and pitching games professionally. This has led me to create a number of theories about why games (and other forms of entertainment) are fun.

These ideas are built on my experiences of adjusting games and game pitches to make them more enjoyable. On the whole this sense of enjoyment is based on the opinions of those making (or paying for the development of) the games (where groupthink is a problem). However, many of the games and their pitches have been evaluated by focus groups and gameplay recordings, performed in relatively controlled settings. Additional information comes from finding patterns in sales figures and other representations of what people enjoy (e.g. the types of magazine available for sale in newsagents).

From these experiences I've attempted to find simple theoretical justifications for the behaviour I've observed. In some cases, these theories have some validation through external research, but on the whole are not experimentally validated. I take the view that it is better to have some sort of theory rather than nothing, and indeed these theories have been very useful in guiding my work.

These ideas will focus on the fun (or more generally the source of motivation) provided by computer games however I believe there are many generalities that can be made from them.