How to Solve Nonograms: A Beginner's Guide
A nonogram is a grid of squares with numbers along the top and the left side. Shade the right squares and a picture appears. Nonograms go by many names (griddlers, hanjie, picross, paint by numbers), but the rules are the same everywhere, and a well-made one can always be solved by logic alone.
How the clues work
Each number is a run of shaded squares in that row or column, in order. A row clue of 3 1 means: somewhere in the row there is a run of three shaded squares, then at least one blank square, then a single shaded square. Nothing else in the row is shaded. The gap between runs can be any size, but it is always at least one square.
Use two marks: shade (or fill) squares you know are filled, and put a small dot or X in squares you know are empty. The X's are just as important as the shading.
Technique 1: overlap
This is the one that gets you started. Take a row of 10 squares with a clue of 7. Slide the run as far left as it can go: it covers squares 1 to 7. Slide it as far right: squares 4 to 10. Squares 4 through 7 are covered either way, so they must be shaded. Any clue larger than half the row gives you free squares this way. Start every puzzle by checking the big numbers.
The same idea works for several runs. For 4 3 in 10 squares, the runs plus the one gap fill 8 squares, leaving 2 squares of slack. Any run longer than the slack has overlap: here, the middle two squares of the 4 and the middle square of the 3.
Technique 2: edges and completed lines
Once a shaded square touches the edge of the grid, you know exactly where that run starts. If the first square of a row is shaded and the first clue is 3, shade squares 1 to 3 and put an X in square 4. And when a row has all of its runs placed, X out every other square in it. Those X's feed the columns that cross it.
Technique 3: reach
A run can only reach so far from a square you know is shaded. If a column's only clue is 2 and square 6 is shaded, the run lies within squares 5 to 7, so every other square in that column is empty. Look for squares no run can reach and X them out.
Work back and forth
Solving is a loop: each row you advance gives new information to the columns, and each column gives some back. Move across the rows, then down the columns, and repeat. When you stall, look for the most constrained line (big clues, or lots of marks already) and look again.
Common beginner mistakes
- Guessing. A properly made nonogram never needs it. If you are guessing, you missed a deduction somewhere.
- Forgetting the X's. Empty squares are information. Mark them.
- Losing track of which run is which. Cross off each clue number as you place its run.
Start with a small grid and a pencil. Once overlap and edges feel natural, the larger puzzles open up. Our large print nonogram books each begin with warm-up grids and end with full solutions.
