How to solve a nonogram one justified square at a time

Read a clue as an ordered list of groups

A nonogram tells you which squares to fill using clues beside each row and above each column. Each number gives the length of one consecutive filled group. Separate groups in the same line must have at least one empty square between them. The order of the clue numbers matters: a row marked 1, 2 needs a one-square group before a two-square group, reading left to right.

Columns follow the same rule from top to bottom. The two groups are not interchangeable, and a clue of 1, 2 does not mean one three-square group. Every filled square participates in both a row and a column, so a placement that looks fine horizontally may still contradict its vertical clue. The puzzle is solved by satisfying both sets of constraints at the same time, not by recognizing an image and filling what seems to belong to it.

Start with the actual size and controls of this puzzle

Break Club’s main Nonogram game, also called Trama breve, has three selectable five-by-five puzzles. Choosing another puzzle starts that board from its beginning. Read its new row and column clues before marking cells. A pattern you remember from a previous selection is not evidence for the same square in the new puzzle.

The compact grid lets you inspect a complete line without dealing with dozens of positions. Use that advantage to compare every legal placement of a clue. Keep filled, deliberately empty, and unresolved squares conceptually separate. A square that you have not decided about is not yet proved empty. In the main version, progress does not persist after reloading or closing the page, so allow for that before leaving an unfinished puzzle.

Use overlap to find squares shared by every placement

Consider a line of five squares with a single clue of 3. The three-square group can occupy positions 1–3, 2–4, or 3–5. Position 3 belongs to all three possibilities, so it must be filled. Position 1 occurs in only the first placement, and position 5 only in the last. You cannot confirm either edge from this clue alone.

This gives you one definite square without choosing an entire group location. Once a crossing column adds information, compare the remaining placements again. If position 1 is proved empty, the 1–3 placement disappears. The remaining 2–4 and 3–5 placements share positions 3 and 4, so both become definite fills. A justified empty square can therefore produce new positive information. The reasoning comes from the available space and surviving placements; it is not a rule to fill the center of every line regardless of its clues.

Include the mandatory gap when fitting multiple groups

A line with clues 1 and 2 needs at least four squares: one for the first group, one empty separator, and two for the second group. In a five-square line, there is only one additional square of flexibility. Write out complete placements in order rather than shifting the groups independently and accidentally deleting the separator.

For example, the filled pattern at positions 1, 3, and 4 forms a single square, a gap at 2, and a two-square group at 3–4. Position 5 must be empty in that complete placement. Filling positions 1, 2, and 3 instead creates one group of three and fails the clue. Filling positions 1, 2, and 4 creates groups 2 and 1, reversing the requested order. Counting a total of three filled squares is necessary in this example but does not establish the correct grouping.

Cross a row deduction with its column

Suppose you have established that a particular row’s center square is filled. That square now constrains the corresponding column. List the column’s allowed groups and keep only placements that include the known fill. If every surviving placement also fills another square, you have a new conclusion to send back to that square’s row.

This back-and-forth is often more effective than trying to finish one line in isolation. Do not force the column to fit a row decision that was only a guess. If there are no column placements consistent with the marks you have made, inspect the earlier assumptions. A contradiction identifies something to review; it does not authorize changing a printed clue. Keep track of which marks follow from a completed argument so you can revise the uncertain step without discarding the rest of the board.

Mark the ends of a completed group carefully

When a line asks for a single group of 3 and you have proved exactly where all three squares are, every other square in that line must be empty. The ends cannot be extended without turning the required group into one of 4 or more. Marking those surrounding spaces empty helps neighboring columns exclude placements.

The same conclusion cannot be applied blindly to a line with several clue numbers. If the clues are 1 and 3, completing the three-square group still leaves the one-square group to locate. You need the mandatory separation, but you cannot declare every remaining square empty. Similarly, seeing three adjacent filled squares does not always mean they are the clue’s complete group if the line also permits a longer group. Compare the actual clue length, known empties, and remaining space before labeling a segment finished.

Repair a contradiction without starting the entire puzzle over

Choose a row or column that no longer has any legal arrangement. Review its filled and empty marks one at a time. Ask which was established by overlap, which came from a crossing line, and which came from a visual guess about the picture. Undo or remove the particular questionable mark rather than repainting everything indiscriminately.

A familiar-looking shape can be misleading, especially early in a small puzzle. The intended image is the result of the constraints, not an extra rule that can override them. If you recognize a possible heart, arrow, or letter, continue checking group lengths instead of using recognition to fill unproved cells. A corrected empty mark may reopen several placements and make the next deduction straightforward. That is normal revision of the board, not evidence that the clues need to be bent to match your first interpretation.

Make your next action explainable without an image

Before painting a square, state the line and the shared condition that requires it. For example: every remaining placement of the row’s three-square group covers the third position. Before marking a square empty, state what excludes it: a completed group, a required separator, or the absence of any permitted placement covering it.

This habit is useful when viewing the puzzle on a narrow screen, enlarging a diagram, or talking through a position with someone else. Use consistent position numbers and distinguish row order from column order. Letters shown in an editorial example label positions; they do not add buttons or new clues to the game. The immediate goal is one defensible fill or empty mark. You can leave other squares unresolved until the crossing information is strong enough, rather than completing a line by making the picture look balanced.

A five-square line with clues 2, 2 has no spare space: two filled squares, one empty separator, and two filled squares use the entire line. All five positions are determined. Compare that with a single clue of 2, which has several possible placements in the same length. The total number of filled squares and the required separators jointly determine how much freedom remains; reading only the first clue number loses part of the problem.