What is a nonogram?
A nonogram is a picture puzzle solved by logic. Each row and column has numbers beside it: the lengths of its runs of shaded cells, in order. "3 1" means a run of three, then at least one empty cell, then a run of one. Shade the cells so every row and column matches, and the shaded cells make a picture. There is nothing to guess: the numbers are enough to work out every cell.
Choose 5 × 5, 7 × 7 or 10 × 10. In Shade mode a tap shades a cell or clears it; in Cross mode it marks a cell you know is empty. Drag along a row or column to change many cells at once. A clue turns grey when its line matches it.
How is your Nonogram time calculated?
Your result is the time from Start until every row and column matches its clue; crosses count as empty, so you don't have to cross out every blank cell. Next to it are the times you pressed Check, which marks any cell that disagrees with the picture, and Hint, which shades one right cell (or fixes a wrong one). There is no rating: no published typical time exists for nonograms built like these.
On a phone, the 10 × 10 grid's cells are smaller than a fingertip, which is why dragging is there; a mouse is quicker on that size. Every picture was drawn for this site, and the clock runs from Start, so reading the clues counts too.
How do you solve nonograms?
Start with the biggest numbers. A run longer than half its line must cover the middle cells, wherever it sits. In a line of 10, the site's code lists every position of one run and counts the cells it always covers:
| Run in a line of 10 | Cells certain to be shaded |
|---|---|
| 6 | 2 |
| 7 | 4 |
| 8 | 6 |
| 9 | 8 |
| 10 | 10 |
- Add up the clue. If the runs plus one gap between each fill the line exactly (4 and 5 in a line of 10), the whole line is known.
- A 0 empties the line. Cross it out at once; its cells help every column they cross.
- Work back and forth. Each cell you settle in a row is a clue for its column, and the other way round. Most puzzles fall line by line this way.
- Use crosses. Marking cells you know are empty makes the remaining room for each run easy to see.
Does every nonogram have exactly one answer?
These do. There are 30 pictures, and each one is shipped only if a solver that works line by line, never guessing, can finish it from the clues alone. A picture that left any cell undecided was redrawn. The site's tests run that solver on every picture, and count the answers of the smaller ones by trying every possibility.
Is nonogram Japanese?
Yes. In 1987 Non Ishida, a Japanese graphics editor, won a competition with pictures made of lit and unlit windows, and the puzzler Tetsuya Nishio published the same kind of puzzle on his own. The collector James Dalgety named them nonograms, after Non, and The Sunday Telegraph printed them weekly from 1990. They are also sold as Hanjie, Griddlers, Pic-a-Pix and Picross; several of those names are brands.
For another grid of yes-or-no cells, try the Binary Puzzle; for one with sums, Kakuro.