What is a nonogram? Picross, griddlers, and hanjie explained

A nonogram is a logic puzzle you play on a grid. Beside every row and every column sits a list of numbers. Each number is the length of one unbroken run of filled squares in that line, in order, with at least one empty square between runs. You fill the grid so that every line matches its numbers, and a picture appears.

A row marked 3 1 in a ten-wide grid holds a run of three filled squares, then a gap of at least one, then a single filled square, in that order. Where the runs sit is what you work out, and only the crossing columns can tell you.

Nonogram vs picross vs hanjie: one puzzle, many names

The puzzle was invented twice in the late 1980s. Non Ishida, a Japanese graphic designer, won a competition with pictures made by lighting windows in a skyscraper and turned the idea into grid puzzles. Tetsuya Nishio arrived at the same puzzle independently. The name nonogram, after Ishida, came from the British puzzle maker James Dalgety when the puzzles started running in a London newspaper in 1990.

Since then the same puzzle has picked up a name wherever it landed:

• Picross, from Nintendo's Mario's Picross on the Game Boy in 1995, is the name most players under forty know.
• Griddlers is the name of a large puzzle community and website.
• Hanjie is the Japanese name, and the one many puzzle magazines use.
• Paint by numbers, pic-a-pix, and crucipixel are other magazine names.

They are all the same rules.

Why it's a logic puzzle

A well-made nonogram never needs a guess. You can prove every square filled or empty from the numbers and the squares you already know. The simplest proof is overlap: a run of seven in a ten-wide row must cover the middle four squares wherever it sits, so you can fill those four before you know anything else. From there, each square you settle shortens the possibilities in the line that crosses it.

A puzzle you can't finish by proof alone counts as broken, and good generators check for it. Every Nounogram you play has been checked for exactly one answer.

How Nounogram changes it

In a nonogram, the empty squares are just empty. In a Nounogram, they hold letters, and you spell a word into every run of two or more letter squares, across and down, with crossing words sharing a letter the way they do in a crossword. The numbers still count the solid squares. So a word that won't fit shows you where a solid must be, and a solid you've proved shows you where a word can't go.

If you've solved a nonogram, you already know half of Nounogram. You can read the other half on the rules page, and today's puzzles are free.