Shadebobs
Translucent blobs that leave smoky trails of light where they overlap — the Amiga's "bobs" drawn additively against the palette.
A shadebob is a "bob" (blitter object) that does not write a fixed colour but increments the colour index of the pixels it covers. Where several bobs pass over the same point the increments add up, and with a palette that rises smoothly in brightness, soft, smoky trails build up wherever the motion has been densest.
The effect was an Amiga favourite because the blitter could draw bobs quickly, and the motion paths were usually pulled from sine tables. The result recalls metaballs and plasma in its softness, but here the shape comes from accumulated overlap rather than a thresholded field.