How to solve a nonogram
Fill the certain cells in the biggest clues first, cross out what can’t be filled, then let each row help the columns and each column help the rows.
How it works
A nonogram gives you a clue for every row and column. You fill cells to make a picture that makes every clue true.
Solve it one line at a time. For each row or column, ask which cells every possible placement agrees on. Fill those and cross those. Then switch direction: what you just learned changes the columns.
Start with the lines that have the least slack. A clue that fills its whole line is free. A long block in a short line gives cells through the overlap rule.
A checklist for every line
One: is the clue already complete? Cross the rest. Two: does the overlap rule fill anything? Three: is there a filled cell near an edge or a cross? Work out how far its block can reach. Four: are there cells no block can reach? Cross them.
Go around the rows, then the columns, and repeat. Stop only when a whole pass changes nothing. On a good puzzle, that is when it is solved.
Worth memorizing
Biggest clues first.
Less slack means more sure cells.
Crosses are as useful as fills.
They are walls for the other direction.
Alternate rows and columns.
Each pass feeds the next.
Practice
0 of 4 rightWhich rows can you fill completely at the start?
Row 5 says 5. Which of its cells does the overlap rule fill?
Column 1 says 3, and rows 2 to 4 are filled. What happens to its other cells?
Row 1 says 2 2 and both ends are crossed. What does it become?