demoeffect n.

[demoscene] What among hackers is called a display hack. Classical effects include "plasma" (colorful mess), "keftales" (x*x+y*y and other similar patterns, usually combined with color-cycling), realtime fractals, realtime 3d graphics, etc. Historically, demo effects have cheated as much as possible to gain more speed and more complexity, using low-precision math and masses of assembler code and building animation realtime are three common tricks, but use of special hardware to fake effects is a Good Thing on the demoscene (though this is becoming less common as platforms like the Amiga fade away).

--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.