Piet is an esoteric programming language designed so that programs resemble abstract art. It was named after the Dutch painter Piet Mondrian.
Programs aren't written in text but instead drawn on an image. Contiguous areas of a single color represent numbers while transitions from one color to another encode the instructions. Piet uses six different colors in three shades (dark, normal, bright). Program flow starts in the upper left corner of the image and moves rightwards, initially but it can move pretty much all over the image eventually. Loops are, appropriately, actual loops for the program flow in the image.
See also: [[eso:Piet|Esolangs]]