History of nonograms

The Wikipedia article on Nonograms says the Japanese graphic editor Non Ishida won a 1987 contest in Tokyo. Her puzzle used numbers to design pictures from skyscraper window lights. The professional puzzler Tetsuya Nishio invented the same kind of puzzle independently and published it separately.

The Wikipedia article on Nonograms says Ishida published a book called Window Art Puzzles in Japan in 1988. The UK puzzle collector James Dalgety saw her puzzles and offered to help publish them worldwide. Dalgety coined the word 'nonogram' from 'Non' and 'diagram'.

The Wikipedia article on Nonograms says Dalgety made a deal with The Sunday Telegraph. The newspaper began to publish Ishida's nonograms every week, starting in 1990. The weekly puzzle reached a wide readership in the United Kingdom.

The Wikipedia article on Picross says Nintendo released Mario's Picross for the Game Boy in 1995. Nintendo trademarked the name Picross, short for picture crossword. This site never uses 'Picross' as a product name because Nintendo owns the trademark.

The Wikipedia article on Nonograms says The Sunday Telegraph ran a competition in 1998. Readers voted for a new name, and 'Griddlers' won. Many players and sites still use this name today.

In 1996, researchers Ueda and Nagao proved that solving a general nonogram is NP-complete. NP-complete problems have no known fast method that works for every case as the grid grows larger. Well-designed puzzles avoid this problem because they are line-solvable. A line-solvable puzzle needs only row and column logic, with no guessing. The generator on this site checks every puzzle for this property before it appears to a player.

A solver checks a finished set of clues and reports whether they lead to one solution. A generator creates new puzzles and checks each one the same way. This site uses both tools, built from the same line-solving code.