Nonograms are picture puzzles solved with numbers. Each clue tells you how cells in a line are grouped, and step by step the clues reveal a hidden image.
The rules
- The numbers beside each row and above each column are clues.
- Each clue lists the lengths of the runs of filled cells in that line, in order. "3 1" means a run of three, then at least one gap, then a single cell.
- Fill cells so every clue is true. A finished grid reveals a picture.
Three ideas to start
1. Big clues first: the overlap trick
In an 8-cell row with the clue 6, the run of six can start at cell 1, 2 or 3. Whichever it is, cells 3 to 6 are always filled. Fill them now. In general, a run of length k in a line of length n always covers its middle 2k − n cells, when that number is positive.
This works with several runs too. Add up the runs plus one gap between each, and compare with the line length. "3 4" in a 10-cell line takes 3 + 1 + 4 = 8 cells, leaving 2 cells of slack. Any run longer than the slack has a guaranteed overlap.
2. Zeros and full lines
A clue of 0 means the whole line is empty: cross it all. A clue equal to the line length means it's all filled.
3. Use crosses
Crosses mark cells you know are empty. They matter as much as filled cells: once a run is complete, cross the cells at both ends, and the crossing lines get new information.
Where nonograms come from
Nonograms were invented independently in 1987 by Japanese graphic editor Non Ishida and puzzle maker Tetsuya Nishio. The name combines "Non" and "diagram". They became a worldwide hit through newspapers in the 1990s and Nintendo's Picross games.