A program with the same approximate purpose as a kaleidoscope: to make pretty pictures. Famous display hacks include munching squares, smoking clover, the BSD Unix rain(6) program, worms(6) on miscellaneous Unixes, and the X kaleid(1) program. Display hacks can also be implemented by creating text files containing numerous escape sequences for interpretation by a video terminal; one notable example displayed, on any VT100, a Christmas tree with twinkling lights and a toy train circling its base. The hack value of a display hack is proportional to the esthetic value of the images times the cleverness of the algorithm divided by the size of the code. Syn. psychedelicware.