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" (with other Windmill Software games such as Digger). Also, there is a reverse engineered variant from Andrew Jenner, called Styx Remastered.

Development
Styx uses the same game engine as two other Windmill Software games, The Exterminator and Moonbugs, and these were some of the few programs to make use of the 16-color quasi-graphics CGA mode (normally the CGA could only use 4 or 2 color graphics). However, it was possible to play on a monochrome monitor as long as the graphics card also supported color graphics (e.g. a Genoa Color Graphics Card).

Styx, The Exterminator, and Moonbugs set CGA 320x200x4 mode on the title screen by directly manipulating the video registers; this causes them to display a screen full of garbage on later video cards. The in-game graphics also will only occupy half the screen due to technical differences between CGA and EGA/VGA, however the games can be patched to work correctly on VGA.