A Quake hack that amazed people back in the day.
Basically, ttyquake is a Quake wrapper for Linux. It wrapped all svgalib calls and perverted those to corresponding calls to aalib library.
For laymen: It's a version of Quake that can be played on character-based terminals, in terminal emulators or in text mode. It just renders everything as ASCII art.
There was no color or sound support, though. Basically, on 80x25 terminal you couldn't see a damn thing, but with small font and huge terminal window, it looked pretty impressive.