A picture puzzle invented twice, published in a magazine, and then largely forgotten until the internet found it again.
Nonograms — also called paint-by-numbers, griddlers or picross depending on where you met them — have one of the strangest publication histories of any modern puzzle.
They were invented independently twice, and for a while it looked like the idea would simply disappear.
Two inventors, no contact
In the late 1980s a Japanese puzzle designer created a picture-grid puzzle for a competition, and around the same time an American designer developed a very similar idea separately.
Neither knew about the other. This happens more often in puzzle design than you would expect, because the space of good ideas is smaller than it looks.
Why it nearly vanished
The puzzle needed a grid with numbers along the edges, which is expensive to typeset in a newspaper and awkward to print at small sizes. That alone kept it out of the daily-paper boom that carried Sudoku.
It survived in Japan and in a handful of puzzle magazines, mostly on the strength of the reveal — finishing a Nonogram produces an actual picture, which no other grid puzzle does.
The internet fixed the printing problem
Once puzzles moved to screens, the typesetting constraint disappeared. Nonograms could be rendered at any size with no printing cost, and a puzzle that had been niche for twenty years found a large audience very quickly.
It is one of the few puzzle formats that is genuinely better on a screen than on paper.