A pretty good emulation of AmigaOS ~1.3 from the late 1980s.
This site has been around for a long time and is related to the oldskool demoscene (http://pouet.net) and chiptune music scene (https://www.youtube.com/watch?v=GH7eUlri4yM).
Unfortunately, apart from the neat OS emulation, it does a rather poor job at communicating what it is about or linking to interesting samples of the art.