Nonogram Rules: How to Play, Strategies and Variations

What is a nonogram?

A nonogram is a grid puzzle in which number clues tell you which cells to shade. Every row has a clue to its left and every column has a clue above it. When you have shaded exactly the right cells, they form a hidden picture: a cat, a teapot, a sailing boat or, in the smallest grids, a simple shape like a heart.

You may know the puzzle by another name. It is sold as Picross, Griddlers, Hanjie, Paint by Numbers and Pic-a-Pix, among others, but the rules are identical under every label. Whatever the name, the puzzle needs no arithmetic beyond counting and no general knowledge at all.

If you enjoy the careful elimination of Sudoku, nonograms will feel familiar: every cell can be deduced, and guessing is never required in a well-made puzzle. The difference is the payoff. Instead of a grid of digits, you finish with a small piece of pixel art.

A short history

Nonograms were invented independently in Japan in the late 1980s. In 1987 the graphics editor Non Ishida won a competition in Tokyo with pictures designed as patterns of lit and unlit windows on skyscrapers, and went on to publish grid puzzles built on the same idea. At around the same time the professional puzzle author Tetsuya Nishio created the same kind of puzzle on his own and published it in a different magazine.

The puzzles reached Britain in 1990, when James Dalgety coined the name "Nonograms" (after Non Ishida) and The Sunday Telegraph began printing them weekly. Nintendo then brought the format to a huge new audience as Picross, short for "picture crossword", with Mario's Picross on the Game Boy in 1995. Picross games have appeared on Nintendo hardware ever since.

The puzzle also interests mathematicians: solving a general nonogram has been shown to be NP-complete, which is a formal way of saying that very large grids can be genuinely hard. You can read more in the Wikipedia article on nonograms.

The core rules

A nonogram has only a handful of rules. Every puzzle, from a 5×5 beginner grid to a 30×30 masterpiece, follows these five:

1. 1Each number is a block of shaded cellsA clue of "4" means four shaded cells in a row, touching each other, somewhere in that line. A clue of "3 1" means a block of three and a separate block of one.
2. 2Blocks appear in the order givenRow clues read left to right and column clues read top to bottom. In a row clued "3 1", the block of three always comes before the single cell.
3. 3Blocks are separated by at least one empty cellTwo blocks in the same line can never touch. There may be several empty cells between them, but there is always at least one.
4. 4Every cell is either shaded or emptyThere is no third option. Solvers mark cells they know are empty with a small X or dot, which is just as important as shading.
5. 5The puzzle has one solutionA well-made nonogram can be solved by logic alone, and every row and column clue is satisfied by exactly one picture. A row with a clue of "0" (or no clue) is completely empty.

Those rules have a useful consequence: you can work out the minimum space a clue needs. The clue "3 1 2" needs 3 + 1 + 1 + 1 + 2 = 8 cells, counting one gap between each block. In a 10-cell row that leaves only two spare cells, which is why long clues are such good starting points.

A worked example

Here is a complete 5×5 nonogram. The clues sit in the blue margins and the shaded cells reveal a heart. The X marks show cells the solver proved were empty.

Check it against the rules. The top row reads "2 2": two shaded cells, a gap, then two more. The second and third rows are full, so their clue is "5". The middle column is clued "4", and you can see its four shaded cells run from row two to row five without a break. The two full rows are the natural place to start: a clue of 5 in a 5-cell line leaves no choice at all.

How to play: a step-by-step method

You can solve cells in any order, but this routine keeps you moving and stops you from missing easy deductions:

1. Fill the certain lines first. Any clue that equals the line length fills the whole line, and any line clued 0 is empty. Mark both immediately.
2. Look for big clues. A clue that is more than half the line length always forces some cells in the middle. The overlap method below shows exactly which ones.
3. Mark empty cells as you find them. An X is information. It splits a line into smaller spaces and often decides where a block can go.
4. Switch direction constantly. Every cell you shade in a row is also a cell in a column. After each deduction, check the crossing line for something new.
5. Close finished lines. When a row or column has all of its blocks in place, fill the rest of it with X marks so you never have to think about it again.
6. Repeat until the picture appears. Sweep the grid row by row and column by column. Each pass unlocks more cells, and by the end the image usually tells you whether something is off.

Strategies that solve almost any grid

Nearly every nonogram yields to a small set of techniques. Learn these six and you can tackle grids of any size.

The fastest way to make these habits automatic is to solve a small grid every day. Nonograms.gg publishes a free daily puzzle, so you can practice the overlap method on a fresh grid every morning.

Popular variations

The classic black-and-white grid is the most common form, but several variants add a twist to the same rules:

• Color nonograms. Each clue number has a color, and the picture uses several colors. Blocks of different colors may touch without a gap, while blocks of the same color still need one.
• Mega clues. Found in some Picross games, a mega clue spans two rows or two columns at once and describes shapes that cross between them.
• Picross 3D. Nintendo's three-dimensional take on the idea: you chip away cubes from a block to reveal a sculpture, using clues on each face.
• Triangular grids. Sometimes called Triddlers, these use triangular cells with clues running in three directions instead of two.
• Giant grids. Puzzle magazines publish nonograms of 40×40 cells and more, sometimes split across several linked sections. The rules are unchanged, but the bookkeeping becomes the real challenge.

Common mistakes

The single biggest mistake is not marking empty cells. Beginners shade what they are sure of and leave everything else blank, then lose track of which blanks are proven and which are unknown. An X costs one tap and saves a lot of rechecking.

The second is miscounting. An off-by-one error in a long row can ripple through a dozen columns before you notice. When a block is placed, count it again against the clue before moving on.

Third, many solvers work in only one direction, sweeping rows for too long. Every deduction in a row is also a deduction in a column, so switch often. Finally, resist the urge to guess. If you feel stuck, you have almost certainly missed an overlap or a gap that is too small for the next block, and a slow sweep of every line will usually find it.

Grid sizes and difficulty

Difficulty comes mostly from size and from how many cells can be settled by simple overlaps. A 5×5 or 10×10 grid is ideal for learning, since overlaps and edge logic solve it outright in a few minutes. 15×15 grids need regular gap analysis and cross-checking, and are the standard size for many newspaper and app puzzles.

Grids of 20×20 and beyond reward patience and tidy marking more than clever tricks. The picture itself becomes a helpful check at this size: if a line you just shaded makes the drawing look wrong, recount before continuing.

Nonograms sit comfortably alongside other shading puzzles. Nurikabe and Star Battle also ask you to decide which cells are filled, and if you prefer numbers to pictures, Kakuro is a good next step.

Frequently asked questions