What is a nonogram?
A nonogram, also called a picross or griddler puzzle, is a grid puzzle where you fill in squares to reveal a hidden picture. Numbers beside each row and above each column tell you the lengths of consecutive filled squares in that line, in order, with at least one blank square between groups. For example, a clue of 3 1 in a row means there is a run of three filled squares, then at least one blank, then a single filled square, somewhere in that row. Your job is to combine the row and column clues until only one picture fits, and the satisfaction comes from watching an image emerge from pure logic.
Nonograms range from tiny five-by-five grids that take a minute, to enormous puzzles with hundreds of rows that take hours and reveal detailed pictures. They are popular in puzzle books, newspapers and video games, and they are excellent brain training because they require deduction, not guessing: every filled square should follow logically from the clues and the squares already placed. They are also wonderfully accessible, because the rules take thirty seconds to learn, yet the hardest puzzles challenge even experienced solvers. Children can enjoy small nonograms, while adults can lose themselves in large ones.
The history of nonograms is charmingly modern. They were invented in the late 1980s by a Japanese graphics editor who wondered whether a picture could be encoded as numbers, and they spread through puzzle magazines and then to handheld games, where they became a beloved pastime. Unlike crosswords, they need no language knowledge, so the same puzzle works in any country. That universality, plus the pleasure of revealing a picture, explains why they have endured for decades.
How clues work
Each clue is a list of run lengths. A row with clue 2 2 in a ten-wide grid must contain two pairs of filled squares, separated by at least one blank, with the remaining squares blank. The order matters: the first run in the clue is the leftmost run in the row, and the same applies top to bottom for columns. A clue of 0 means the entire row or column is blank, which is valuable information, because it immediately eliminates a whole line. The tool on this page demonstrates clue computation: given a row of filled and blank squares, it works out the clue, which is the reverse of solving but teaches the logic perfectly.
Start solving with the lines that are most constrained. A row whose clue adds up to almost the full width leaves little room for movement, so many squares are forced. For example, a clue of 7 in a ten-wide row must overlap in the middle, so the central squares are certainly filled. Fill those, then use columns to narrow down the remaining possibilities, then return to rows. Cross off completed lines, mark squares you know are blank with a dot or cross, and never guess if you can deduce: guessing feels faster but usually creates errors that are painful to undo.
Solving strategies that actually help
Overlap is the most powerful technique. If a run of length five could start in any of the first six positions of a ten-wide row, the squares covered by every possible placement are certainly filled. Edge logic helps too: if a run must touch the edge, or cannot touch it because of a blank you have marked, its position narrows quickly. Small clues at the edges often pin down a run's location, and a single marked blank can split a row into independent segments that are much easier to solve. Work systematically, line by line, and revisit lines after each new deduction, because one new square often unlocks several others.
For larger puzzles, work in passes. First fill all forced squares from overlapping runs, then mark all blanks that cannot be part of any run, then repeat. Keep the picture in mind: if a shape is emerging, such as an animal or a letter, that can guide you, but do not let it override logic, because the picture should be a check, not a guess. If you get stuck, check for a missed overlap or a blank you forgot to mark; most stuck positions are caused by one overlooked deduction, not by a genuinely ambiguous puzzle. Well-designed nonograms have a unique solution reachable by logic alone.
Making and printing your own puzzles
Making a nonogram is as satisfying as solving one. Draw a small picture on graph paper, ideally five by five or ten by ten, then compute the row and column clues by counting runs of filled squares in each line. Test it by solving it yourself or asking a friend to solve it, and check that the solution is unique: if two different pictures fit the same clues, add or remove a square to break the ambiguity. Simple, bold pictures with clear shapes work best, because fine detail becomes unreadable in a small grid. Letters, hearts, stars and simple animals are excellent first designs.
Nonograms are ideal for classrooms, waiting rooms and travel, because they need only a pencil and a printed grid. Print a few puzzles at different sizes, keep a pencil with an eraser handy, and start small before attempting larger grids. The tool above shows how clues are computed from a fixed example grid, which is a perfect teaching aid: change the example in your head, compute the clue, and check your reasoning. Once clue logic clicks, solving becomes a calm, absorbing pleasure that rewards patience and careful thinking, one square at a time.
Advanced techniques and puzzle variations
Once basic overlap and edge logic feel comfortable, advanced techniques open up larger puzzles. One is the use of gaps: if a marked blank splits a row, each segment can be solved independently, and a run that is too long for one segment must belong to another. Another is counting minimum space: a clue of 2 3 needs at least two plus one plus three, or six squares, plus any blanks, so a short segment that cannot fit the whole clue must contain only part of it, which narrows placements. Colour nonograms add another layer, where each clue is coloured and runs of different colours may touch without a blank, while a run of the same colour still needs separation. These variations reward the same careful logic, with one extra rule to track.
Multi-grid and three-dimensional variants exist too, including puzzles where several grids share clues, and large picture puzzles built from many small nonograms that combine into one image. If you enjoy nonograms, try increasing grid size gradually, from ten by ten to fifteen by fifteen and then to twenty by twenty, rather than jumping straight to a huge puzzle, because the techniques scale but the patience required grows quickly. Keep a pencil, not a pen, for large puzzles, mark blanks clearly with a small cross or dot, and take breaks when stuck: a fresh look after ten minutes often reveals the deduction you missed. The best puzzles feel challenging but fair, and the moment the picture finally emerges is worth every careful square.
Quick checklist for solving: read all row and column clues first, fill forced squares from overlapping runs, mark blanks that cannot be part of any run, cross off completed lines, and revisit every line after each new deduction. Use a pencil, work systematically rather than guessing, and take a short break if stuck, because a fresh look often reveals the missed overlap. For making puzzles, draw a bold simple picture, compute clues carefully, test for a unique solution, and start friends on a small grid before offering a larger challenge.
One last habit makes all of this stick: write down what actually happened, compare it with what you planned, and adjust next time. If a journey took longer than expected, a bill was higher than estimated, a tank emptied early, a trip log was incomplete, a notice date was misunderstood, a letter needed rewriting, a quote missed a cost, a puzzle clue was misread, or a shopping list missed an item, note the reason while it is fresh. Small, honest corrections compound quickly, and within a few uses your plans become accurate, your costs become predictable, and the tool becomes a trusted part of your routine rather than a one-off calculation.