Most “pixel puzzles” use the rules of a nonogram, also called Picross, Griddlers, Hanjie or Paint by Numbers. The numbers beside each row and column describe ordered runs of filled cells. Solve the puzzle by placing only cells that every legal arrangement permits, marking proven empty cells, and alternating between rows and columns until the hidden picture is forced. This guide covers that standard row-and-column format; a game using the name “pixel puzzle” may add different rules, so check its instructions first.
What a pixel puzzle is—and what this guide covers
A standard nonogram is a rectangular grid with clues printed along two edges. A row clue describes the filled cells in that row; a column clue describes the filled cells in that column. Every square belongs to one row and one column, so a decision in either direction immediately constrains the other.
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The labels vary by publisher and region. You may see Picross, Griddlers, Hanjie, Nonocross or Paint by Numbers. The common mechanic is the same: infer a binary picture (filled or empty) from run lengths rather than from a visual preview. The beginner rules in this article are summarized in the ItsyBitsy Games guide to solving nonograms (dated June 13, 2026) and the Nonograms.games beginner guide.
Some apps use “pixel puzzle” for color nonograms, picture-placement games, or other formats. Those may permit adjacent runs of different colors, use symbols instead of filled cells, or add special tiles. Do not apply the monochrome method below until the particular game confirms that its clues represent separated runs in rows and columns.
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The rules you need before making a mark
Numbers describe runs, not coordinates
A clue is a sequence of run lengths, read from the edge toward the line. A clue of 3 2 means one contiguous block of three filled cells, then—somewhere to its right or below—a contiguous block of two filled cells. It does not mean “fill cell 3 and cell 2,” and it does not specify the exact starting position.
The order is fixed. In a row with clues 2 1, the pair must occur before the single cell. Reversing those groups would satisfy the same totals but violate the clue.
Separate runs need a gap
Distinct runs must have at least one empty cell between them. Thus 3 2 requires at least six cells: three filled, one empty separator, and two filled. The separator is mandatory even when the puzzle interface does not ask you to mark it explicitly. Cells inside one run, however, are adjacent; placing an empty square inside a run would split it and make the clue impossible.
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For a line of length L and clues a₁…aₖ, calculate the minimum occupied space as:
minimum space = a₁ + a₂ + … + aₖ + (k − 1)
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The final term counts the required one-cell gaps. If that minimum equals L, the entire arrangement is fixed. If it is smaller, the groups can slide, and only cells common to every legal placement are immediately safe.
Full and zero clues are automatic deductions
- If a single clue equals the line length, fill the whole line. A length-5 row with clue
5is five filled cells. - If the game displays a zero clue, the line contains no filled cells. Mark every square empty if the interface supports X marks; otherwise treat them as known blanks.
- A line whose minimum exactly equals its length has fixed runs and fixed separators, even when it has several clues.
Rows and columns must agree simultaneously. A line that appears complete is not evidence that the puzzle is solved until its crossing lines also meet their clues.
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Set up a grid that preserves what you know
Digital games usually provide two tools: a fill action and an empty or X mark. On paper, use a solid square for filled cells and a small dot or X for confirmed empties. Leave undecided cells blank. This three-state notation—filled, empty, unknown—prevents a guess from silently becoming a fact.
Write the clues in groups and leave enough visual space to count. On a large paper grid, number every fifth row and column or use a ruler. On a phone or tablet, zoom before counting and verify whether a tap toggles a cell, cycles between fill and X, or requires separate buttons. Misreading the input mode is a common source of apparent logic errors.
A reliable beginner solving routine
Work through the following loop rather than trying to recognize the picture. The sequence is deliberately conservative: every fill should follow from a clue, an intersection, or a previously proven empty square.
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- Scan for forced lines. Inspect every row and column for a clue equal to its length, a zero clue, or a set of clues whose minimum space equals the line length. Fill the runs and mark the required gaps.
- Find high-overlap runs. For a long clue that can slide, write or visualize its leftmost and rightmost legal positions. Any cell covered in both extremes—and therefore in every position between them—is filled. Do this separately for each run while respecting the gaps between groups.
- Record proven empties. When a run is complete, mark the cells immediately outside it as empty whenever the line boundary or neighboring clues proves they cannot be filled. Marking empties is not cosmetic: it stops a later fill from accidentally extending a finished run.
- Recheck the crossing lines. Every newly filled or emptied square changes one perpendicular clue. Read that row or column again from the edge, narrowing the possible starts of its runs.
- Finish constrained groups. If a row now contains a run of the required size, mark the cells that must separate it from the next run and rule out extensions beyond its clue. If a clue has already been accounted for, remaining unknown cells in that line are empty.
- Alternate directions continuously. Move back and forth between rows and columns. A column deduction may create a full row; that row may then fix another column. The puzzle is a network of intersections, not a set of independent lines.
- Confirm before advancing. Count each run from left to right (or top to bottom), including separators. If the sequence does not match exactly, undo the newest assumption before making more marks.
- Stop only when both directions agree. A finished image can look convincing while containing an illegal extra cell. Completion requires every row and every column to satisfy its clue list.
How overlap deductions work
One run in a five-cell line
Suppose a five-cell row has clue 4. The block can start in position 1 or position 2:
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| Possible placement | Cells |
|---|---|
| Starts at 1 | Filled, filled, filled, filled, empty |
| Starts at 2 | Empty, filled, filled, filled, filled |
Positions 2, 3 and 4 are filled in both arrangements, so those middle three cells are safe. The outside cells remain unknown until another clue crosses them. This is the basic overlap technique described by Nonograms.games.
Several runs and the minimum-space calculation
Consider a seven-cell line with clues 3 2. The minimum is 3 + 2 + 1 = 6, leaving one spare cell. The only legal placements are:
| Placement | Pattern |
|---|---|
| Spare cell before the first run | · 3 1 2 |
| Spare cell after the first run | 3 1 2 · |
Here the three-cell run may begin in position 1 or 2, while the two-cell run may end in position 6 or 7. The overlap calculation identifies the cells that never move; the separator remains mandatory in both arrangements. On paper, write the actual squares rather than relying on the shorthand pattern so that your row and column counts stay aligned.
Overlapping a run after partial information
Suppose a row has clue 6 in a ten-cell line, and two adjacent filled cells are already known in positions 4 and 5. The run must include them, but it may extend left or right. Place the six-cell block at every start that still covers positions 4–5; the intersection of those placements is filled. If an X mark blocks one candidate, remove that placement before calculating the overlap.
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Reading a line that already contains marks
Existing cells divide a line into possible regions. A filled segment may belong to one clue group or may be part of a longer group. Use the clues on either side to decide which.
When a filled segment completes a clue
If a clue is 3 and the line contains three contiguous filled cells, that run is complete. The cells directly before and after it must be empty unless the run touches a boundary. Those empties may unlock the next clue in the sequence.
When a filled segment could extend
Do not mark the ends of a two-cell segment as empty merely because it currently looks complete if the clue could be 4. Compare the segment with the remaining clue lengths and with neighboring X marks. A run is complete only when its size and position are forced by the clue order or by blocking cells.
Using an X to split possibilities
An empty square divides a line into regions. A run cannot cross it, so each clue group must fit entirely on one side or in a region that has enough room. This often turns an apparently flexible clue into a forced placement without any guessing.
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A difficult puzzle may reach a point where no line is full, zero, or an immediate overlap. Stay clue-driven rather than drawing what the picture seems to suggest.
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- Recalculate minimum space. Include every mandatory separator and subtract cells already proven empty. A line that looked loose may now have only one legal arrangement.
- List legal starts for one clue group. Write the earliest and latest start that respect boundaries, neighboring groups, fills and X marks. Intersect those placements to find forced cells.
- Use completed groups as barriers. A finished run plus its separator removes space from the remaining clues. Re-solve the unsolved portion as a shorter line.
- Look for a contradiction in your marks. If every legal placement for a clue crosses an X, one of the earlier marks is wrong. Undo the most recent deduction, not an arbitrary cell.
- Delay guessing. The beginner method is based on deductions, and the cited guides do not establish that every puzzle sold under every “pixel puzzle” label is uniquely solvable without trial. If the game offers a hint, use it as a controlled next step; otherwise record a hypothetical branch separately and be prepared to erase it.
Never fill an uncertain cell merely because it makes a recognizable image. A visually plausible mistake can propagate through many rows before the contradiction appears.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Common mistakes and their fixes
| Mistake | Why it fails | Fix |
|---|---|---|
| Reading numbers as coordinates | A clue gives run lengths and order, not individual positions. | Translate each number into a contiguous block and leave its start flexible until deductions fix it. |
| Omitting the separator | Two groups merge into one longer run. | Reserve at least one empty square between every pair of clues. |
| Filling a “likely” pixel | The picture can support several shapes while clues allow only one exact pattern. | Fill only an overlap, a full-line deduction, or an intersection forced by another line. |
| Ignoring empty marks | Later fills may extend a completed group or cross an impossible boundary. | Mark confirmed blanks and treat them as hard constraints. |
| Solving rows only | Each row has many arrangements until columns restrict them. | After every meaningful row deduction, inspect the affected columns, and vice versa. |
| Calling a line complete too early | A matching-looking run may still be extendable or may belong to a larger clue. | Verify clue size, order, separators and boundary cells before closing the group. |
| Counting from the wrong edge | Run order reverses and a valid-looking placement becomes illegal. | Read each clue consistently from its printed edge; for columns, count from top to bottom unless the interface specifies otherwise. |
Paper and digital solving: practical differences
On paper
The printable Andrews University nonogram worksheet shows the familiar paper-grid format. Use a pencil, keep X marks small, and leave room beside a clue to cross out groups as they become assigned. If an error appears, erase only the suspect deduction and re-check the perpendicular line; sweeping erasures can remove valid information.
On a phone, tablet or computer
Learn the app’s controls before solving a large board. Confirm which icon means filled, which means empty, whether a long press changes modes, and whether completed lines are automatically checked. Zooming can prevent an off-by-one tap, but zooming may hide clue numbers at the edge, so pan back after each set of marks. If the game supplies an error highlight, use it to locate a contradiction, not as permission to fill cells randomly.
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Build the habits in this order:
- Start with small monochrome grids. On a board with few rows and columns, practice translating clues into runs and placing all full-line and zero-line deductions.
- Require an X for every proven blank. This trains you to think in three states instead of treating every unfilled square as equivalent.
- Practice overlap separately. Take a line such as a length-5 clue
4and write all legal placements before marking the shared cells. - Pause after each cascade. When one fill changes a crossing line, stop and solve that line completely before scanning elsewhere. This makes the cause of each deduction easy to audit.
- Move to larger grids only after clean completions. Speed is less important than avoiding guesses; larger boards multiply the cost of one unsupported mark.
A nonogram puzzle book can provide additional paper practice, but check that its pages use standard row-and-column clues if that is the mechanic you are learning. The worksheet above demonstrates the grid format; no particular commercial edition is required.
How to verify a finished puzzle
Perform a final audit instead of relying on the image:
- Read every row from its clue edge and write down the lengths of its filled runs.
- Compare that sequence, including order, with the printed row clues.
- Repeat for every column.
- Check that no filled run is accidentally joined to the next run because a separator was omitted.
- Check that all remaining unknown cells have been resolved; an unmarked square is not automatically empty unless the game treats it that way.
Only when both audits match is the picture logically complete. If one line fails, use its first mismatch to trace back through the crossing cell that created it.
Variants: when these rules stop applying
Standard monochrome nonograms use one kind of filled cell and require an empty separator between distinct runs. A variant may change either assumption. Color nonograms can allow adjacent runs of different colors, and some puzzle apps add symbols, clues inside the grid, irregular boards or special cells. The names Picross, Griddlers and Pixel Puzzle are not guarantees of identical rules.
Before solving a new title, identify three things in its help screen: whether clues are monochrome or color-coded, whether equal or different colors may touch, and whether the board is rectangular with one clue list per row and column. If any answer differs from the standard format, follow that game’s written rule instead of importing the separator and overlap assumptions unchanged.
Quick Recap
The essential method in one checklist
- Interpret each number as a filled run length in fixed order.
- Reserve one empty cell between separate runs.
- Compute minimum space as the sum of run lengths plus the required gaps.
- Complete lines whose minimum equals their length.
- Use earliest-versus-latest placements to find overlap.
- Mark confirmed empties so runs cannot grow illegally.
- Alternate rows and columns after every useful deduction.
- Reject picture-based guesses and undo contradictions.
- Finish only after every row and column matches exactly.
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