This concept was first used as a pixel art, in which a user made a checkerboard where one set of squares contained virus and the other containing the colors intended to be used in the picture. When the virus completes its infection, the squares once covered in virus became an odd mix of surrounding colors, giving the completed image an odd look. Random maps also often include a legend, stating that certain elements represent certain land features, such as vine being forest, metal being cities, and powder being desert.