Nonogram
Nonogram is a picture logic puzzle. Fill cells based on number clues to reveal a hidden image.
Key features
- Grid-based picture logic puzzles
- Number clues for rows and columns
- Multiple grid sizes from 5x5 to 15x15
- Auto-check and mistake highlighting
Guide
Nonogram puzzles, also known as picture logic puzzles or Paint by Numbers, are logic puzzles where you fill in cells on a grid to reveal a hidden picture. Each row and column has a set of number clues that tell you how many consecutive filled cells appear in that line and in what order. A row clue of 3 1 means there is a group of three filled cells, then at least one empty cell, then one filled cell. Using these clues across all rows and columns simultaneously, you deduce which cells are filled and which are empty. This guide covers solving techniques from beginner to advanced, common patterns, and strategies for tackling large grids. The appeal of nonograms lies in the combination of logical deduction and visual reward. Unlike Sudoku, which produces a grid of numbers, a completed nonogram reveals an image. This pixel-art result gives you a tangible reward for your logical work. Small puzzles (5x5 or 10x10) reveal simple icons or shapes. Large puzzles (25x25 or bigger) can depict detailed scenes, animals, objects, or characters. The WebRecast browser version provides puzzles of various sizes suited to different skill levels. Understanding the clue format is the first step. Each row and column has its own set of numbers. These numbers describe, from left to right (for rows) or top to bottom (for columns), the groups of consecutive filled cells in that line. A clue of 5 means five consecutive filled cells somewhere in the line. A clue of 2 3 means a group of two, at least one empty cell, then a group of three. A clue of 1 1 1 means three separate single filled cells, each separated by at least one empty cell. The total filled cells in a line equals the sum of its clue numbers. The most fundamental solving technique is overlap analysis, sometimes called the simple boxes method. Consider a row of 10 cells with a clue of 7. The group of 7 filled cells must fit within the 10-cell row. If you push it as far left as possible, it fills cells 1 through 7. If you push it as far right as possible, it fills cells 4 through 10. The overlap between these two positions is cells 4 through 7. Those four cells must be filled regardless of where the group is positioned. You can mark them as filled without knowing the exact position. Overlap analysis works whenever the sum of clue numbers plus minimum gaps exceeds half the line length. For a line of 15 cells with a clue of 10, the overlap is 5 cells (push left: cells 1-10, push right: cells 6-15, overlap: cells 6-10). For a line of 10 with a clue of 3 3, the minimum space needed is 3 + 1 + 3 = 7, leaving 3 cells of slack. Pushing left places groups at 1-3 and 5-7. Pushing right places them at 4-6 and 8-10. The overlaps are cell 4 (in the first group) and cells 5-7 (second group overlap needs recalculation based on actual positions). Working through overlaps systematically is how you start every puzzle. Start every nonogram by scanning all rows and columns for lines with the largest clues relative to the line length. A clue of 8 in a 10-cell line gives you 6 cells of overlap immediately. A clue of 1 in the same line gives you nothing. Process the most constrained lines first because they provide the most information. Mark all cells you can determine from overlap analysis before moving to other techniques. The second core technique is edge logic. If a line starts with a clue and you know the first cell is filled (from a column overlap, for example), then the first clue group must start at cell 1. You can fill the first N cells where N is the first clue number, and mark the cell after the group as empty (because there must be a gap before the next group). Similarly, if the last cell is filled, the last clue group must end there. Edge logic propagates information from cells you already know to fill in more cells. Marking cells as definitively empty (often marked with an X or dot) is as important as marking cells as filled. When you know a cell cannot be filled, mark it empty. Empty cells constrain where filled groups can go, which in turn creates more overlaps and edge logic opportunities. Every empty cell you mark makes the puzzle slightly easier because it reduces the possible positions for filled groups in that line. Cross-referencing between rows and columns is what makes nonograms work. Filling a cell in a row provides information for its column, and marking a cell empty in a column provides information for its row. After each pass of analysis, switch between analyzing rows and analyzing columns. Information flows in both directions. A cell filled by row overlap analysis might create an edge logic opportunity in its column, which marks a cell empty, which constrains a different row, and so on. This cascading logic is what eventually solves the entire puzzle. The gap analysis technique handles lines with multiple clue groups. Consider a row of 15 cells with clues 2 5 2. The minimum space is 2 + 1 + 5 + 1 + 2 = 11, leaving 4 cells of slack. You know the first group of 2 must start somewhere in cells 1-5 (it cannot start later or the remaining groups would not fit). The middle group of 5 must be somewhere in the middle range. The last group of 2 must end somewhere in cells 11-15. Working out the leftmost and rightmost positions of each group and finding overlaps within each group fills in cells. Contradiction logic is an advanced technique. When you cannot determine a cell directly, assume it is filled and see if that leads to a contradiction (an impossible situation where clues cannot be satisfied). If it does, the cell must be empty. Then try assuming it is empty and check for contradictions. If assuming empty leads to a contradiction, the cell must be filled. This technique is slower because you are exploring hypotheticals, but it resolves cells that pure overlap and edge logic cannot. Color nonograms add another dimension. Instead of just filled and empty, cells can be different colors. Each color has its own clues. Groups of different colors do not require empty cells between them (they can be adjacent), but groups of the same color do. Color nonograms are typically easier per cell than black-and-white nonograms because the color information provides additional constraints. The solving techniques are the same, but you apply them per color. Solving order matters for efficiency. Start with the most constrained lines (largest clues relative to line length). Process all initial overlaps. Then focus on lines where cross-referencing has provided new information (a cell was filled or marked empty by another line analysis). Maintain a mental or visual list of which lines need reprocessing. Each time a cell in a line changes, that line should be reanalyzed. Systematic reprocessing prevents you from missing deductions. Common patterns to recognize include: a line with a single clue equal to the line length (fill the entire line), a line with a clue of 0 (mark the entire line empty), a line where the sum of clues plus minimum gaps equals the line length (there is only one possible arrangement, fill it in completely), and a line where a filled cell is already at the edge (apply edge logic to fill the first or last group and mark the gap). Puzzle difficulty scales with grid size and clue ambiguity. A 5x5 puzzle with large clues might be solvable in under a minute. A 25x25 puzzle with many small clues (like 1 1 1 1 1) can take an hour because small clues create less overlap and more ambiguity. Do not be discouraged by large puzzles. Apply the same techniques systematically, and the puzzle will gradually yield. Every cell you resolve creates new information for cross-referencing. The browser-based nonogram on WebRecast provides an interactive grid where you click cells to fill them and right-click or use a toggle to mark cells as empty. Visual feedback helps you track your progress. The grid updates in real time, and you can see the picture emerging as you solve. This visual feedback is both rewarding and useful because recognizing the emerging image can sometimes give you hints about which cells to fill next. Nonogram solving trains several cognitive skills. Logical deduction improves as you practice applying constraint-based reasoning. Spatial reasoning develops as you work with the two-dimensional grid and cross-reference horizontal and vertical information. Patience and systematic thinking are required because guessing leads to errors that can propagate through the grid. Attention to detail matters because a single mismarked cell can make the puzzle unsolvable. For beginners, start with 5x5 puzzles and focus on mastering overlap analysis. Move to 10x10 when you can solve 5x5 puzzles without mistakes. Progress to 15x15 and then 20x20 as your confidence grows. Track your solving times to measure improvement. The techniques do not change at larger sizes. Only the number of lines to process and the complexity of cross-referencing increases. Nonograms have a dedicated global community. Puzzle magazines, online archives, and mobile apps provide thousands of puzzles. Competitive nonogram solving involves speed-solving standard puzzles. Creating your own nonograms is also a popular activity where you design a pixel art image and generate the clues. The WebRecast version provides a curated set of puzzles that balance difficulty and visual payoff, giving you a satisfying solving experience directly in your browser with no installation required. The key to nonogram mastery is patience and systematic application of the core techniques. Overlap analysis, edge logic, empty cell marking, cross-referencing, and gap analysis will solve the vast majority of puzzles. Contradiction logic handles the rest. Every puzzle is solvable through pure logic without guessing. Trust the process, work methodically, and enjoy watching the hidden picture emerge cell by cell.
Frequently asked questions
How do you play Nonogram?
Use the number clues on rows and columns to determine which cells should be filled. The completed grid reveals a hidden picture.
What is another name for Nonogram?
Nonograms are also called picture logic puzzles, picture cross puzzles, or Paint by Numbers puzzles.
