Styx (Windmill game)
Styx is a video game released by Windmill Software in 1983 as a copy-protected, bootable 5.25" floppy disk for the IBM PC/XT. It is a clone of the 1981 arcade game Qix. In September 2004 the source code of the game became available "for historical interest". Also, there is a reverse engineered variant from Andrew Jenner, called Styx Remastered. It does not work on modern PCs because it requires a genuine Color Graphics Adapter card.