How to solve a Nonogram, one row at a time
The numbers beside each row tell you which cells to fill. Here is how to read them.
A Nonogram is a grid with numbers along the top and the left side. Each number is a run of filled cells in that row or column, in order, with at least one empty cell between runs. A row marked 3 1 has a run of three, a gap, then a single filled cell.
You never need to guess. Work through the rows and columns one at a time, and each one tells you a little more.
Find the overlap
Take a row of 10 cells with the clue 7. Push the run as far left as it goes, then as far right. Cells 4 to 7 are filled either way, so they must be filled.
The quick way to see it: add up the clues and the single gaps between them, and subtract that from the row length. Here 10 − 7 = 3. Any run longer than 3 has cells you can fill right away, 7 − 3 = 4 of them.
Mark the empty cells
Once a row’s runs are all placed, every other cell in it is empty. Mark those cells with an X. Empty cells are clues too, because they stop runs in the columns that cross them.
Start from the edges
A filled cell against the edge must be the start of the first run. If the first clue is 4, fill four cells from the edge and mark the next one empty.
Switch directions
Every cell you fill in a row is new information for its column. Keep switching between rows and columns until the grid is complete.