The rules
Each row and column has a clue: a list of numbers. Each number is a block of filled squares, in that order, with at least one empty square between two blocks. A row with the clue 3 1 holds a block of three, a gap of one or more, and a single square.
Fill the squares the clues ask for, and mark the ones that stay empty (an X helps). When every line matches its clue, the picture is done. A fair nonogram has one solution and never needs a guess.
The overlap: start with the big blocks
Slide a block as far left as it can go, then as far right. The squares it covers in both positions are filled, wherever it really sits.
In a row of 10 with the clue 7, the block covers squares 1 to 7 at the left and 4 to 10 at the right: squares 4 to 7 are surely filled. A quick rule for one block: if it is longer than half the line, 2 × block − line squares in the middle are filled.
The same works with several blocks: push all of them left, then all of them right, and fill the squares where the same block overlaps itself.
Complete and empty lines
A clue that adds up to the whole line, like 4 5 in a row of 10 (4 + 1 + 5), fixes every square. A clue of 0 means the whole line is empty: cross it out at once.
Use the edges
A filled square in the first or second square of a line usually belongs to the first block, and that block cannot start before the edge. If the first clue is 3 and square 1 is filled, squares 1 to 3 are filled and square 4 is empty.
In the same way, a crossed-out square near an edge can leave too little room for a block: cross out the squares before it too.
Cross out, then switch direction
Once a line's blocks are all placed, cross out its other squares. Every X and every filled square is new information for the lines that cross it.
So work in rounds: all the rows, then all the columns, then the rows again. Each pass fills a few more squares, until the picture appears.
Habits that help
- Begin with the longest clues and the fullest lines; they give the most.
- Mark the empty squares as carefully as the filled ones.
- If a line makes no progress, come back to it after its crossing lines have changed.
- Print a few puzzles and try them on paper first: the overlap is easy to see with a pencil.
Questions
- What are nonograms also called?
- Griddlers, hanjie, paint by numbers, picture logic puzzles, logimages in French and Japanese crosswords in Russian.
- Do I ever have to guess?
- Not in a fair nonogram. Every puzzle of Quiltwick and of our printable page is checked to solve line by line.
- How do I read a clue like 2 2 1?
- A block of two, a gap, another block of two, a gap, then one square. The gaps are at least one square long and can be longer.
