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.

[1][2] Also, there is a reverse engineered variant from Andrew Jenner, called Styx Remastered.

[3]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).

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.