Styx was released by Windmill Software in 1983. It is a decent clone of the arcade game Qix (also sometimes known as "Kix"). This is actually a "remastered" version of the game that has been altered to work a bit better on modern computers. Also the game was originally released bootable floppy only game, but this version works like a normal DOS game. (As usual with really old games, run with DOSBox, otherwise it'll probably run too fast in Windows or not work at all.)