Demo effect
A graphics or visual technique used in demos to create "wow" moments — often built on clever mathematical tricks to squeeze maximum output from minimal CPU.
Starting in the late 1980s, demoscenemakers developed a toolkit of rendering techniques to make old processors do the impossible: plasma effects from trigonometric color calculations, tunnel and vortex distortions that warped textures in real time, and flowing copper bars on the Amiga written directly to the blitter. Each effect was a puzzle — how much can I do with the fewest cycles? — and the secret sauce often lay in register tricks, cache optimization, and pre-computed trig tables. A great demo effect wasn't just beautiful; it redefined what the hardware was thought capable of.