Nonograms are one of the most popular and most published puzzle types in recent years, and are known by many names such as Hanji, Paint Logic and Griddlers. However, they are most well known in the gaming community as Picross (which is a contraction of PICture CROSSword) due to Nintendo's usage of the concept in several games.
Originating in Japan circa 1987, the concept spread to magazines and newspapers around the world.
A nonogram involes a grid, with number clues along the side. The aim being to eliminate certain squares, and leave others, which usually form a picture. Numbers indicate the number of squares in that line or column that form part of the picture, and how they are grouped.
There are numerous strategies for solving a Nonogram, the starting point usuallybeing those lines which contain all, or zero blocks. While most lines have insufficient clues to directly identify blocks, certain blocks can be identified as common to all possible solutions (overlap). Once the player has revealed enough of the picture to identify it, some assumptions such as whether the picture is symmetrical, can help the player progress.
Harder puzzles often require 'proof by contradiction' where one of a number of viable solutions is tried, until is is found to contradict the clues in another row or column. This trial and error aspect makes the game type particularly suitable for electronic media over pen and paper.
Recently games such as Picross 3D and Color Cross have added variations to the concept.