The one important feature that sets video games apart from other media like movies or books is the player's ability to interact and be a part of the experience. Just think about it for a moment: A piece of literature defines itself by what it tells and which images it creates in the reader's imagination. Movies are trying to engage and entertain by showing, not telling. The video game medium, while of course being able to tell stories and visualize the action in spectacular ways, requires its audience to take an active part and take control of what's happening on the screen. This is a fundamental difference to the other forms of entertainment media, where the audience is put into the role of a passive consumer. Reading user input and providing immediate on-screen responses, representing the state of the game and prompting the player for more input, this feedback loop operates at the core of every video game.

Input data can originate from various sources and take many different...