Megademo IV 2 is an audiovisual experiment by Artwork.
Quote from http://www.digital-circuits.org/mdiv2/index.html:
This is a quite unusual “scene” demo. As it is unusual in several aspects. It has a very uncommon style using lots of multilayered effects, nearly no 3d scenes and a it has only a “sound-background” instead of the usual, mostly techno-style demo musics.
The other very unusual aspect is that this demo is 100% system independent, it is portable. This was achieved by programming the demo in 100% ANSI C and using no hardware or OS-specific functions (special interrupts etc.)