Cite
 
smoking clover: n.

[ITS] A display hack originally due to Bill Gosper. Many convergent lines are drawn on a color monitor in such a way that every pixel struck has its color incremented. The lines all have one endpoint in the middle of the screen; the other endpoints are spaced one pixel apart around the perimeter of a large square. The color map is then repeatedly rotated. This results in a striking, rainbow-hued, shimmering four-leaf clover. Gosper joked about keeping it hidden from the FDA (the U.S.'s Food and Drug Administration) lest its hallucinogenic properties cause it to be banned.