How to Play Nonogram

Nonogram (also known as Picross, Griddlers, or Paint by Numbers) is a picture logic puzzle. This guide explains the rules, how to read clues, how to fill and mark cells, and how to complete a puzzle correctly. It is written for beginners and for players who want a clear reference to standard nonogram rules.

---

Objective

The goal is to reveal a hidden picture by filling cells in a grid according to number clues. Each row and column has clues that tell you:

• How many consecutive filled cells appear in that line
• The order of those groups (from left to right, or top to bottom)

A completed nonogram shows a picture or pattern when all the correct cells are filled.

---

The Nonogram Grid

• The grid has rows and columns (common sizes: 10x10, 15x15, 20x20)
• Each cell can be in one of three states: empty, filled, or crossed (marked as definitely empty)
• Number clues appear along the left side (for rows) and the top (for columns)

---

Reading the Clues

Each clue is a list of numbers. For example, a row clue of 3 1 2 means:

1. A group of 3 consecutive filled cells
2. Followed by at least one empty cell
3. Then a group of 1 filled cell
4. Followed by at least one empty cell
5. Then a group of 2 consecutive filled cells

The groups must appear in exactly that order, with at least one empty cell between each group.

---

Cell States

• Empty: The default state, not yet decided
• Filled: You believe this cell is part of the picture (shown as a dark square)
• Crossed: You know this cell must be empty (shown with an X mark)

Marking cells as crossed helps you keep track of cells you've ruled out.

---

Making Valid Moves

To solve a nonogram:

1. Look at the clues for a row or column
2. Determine which cells must be filled based on the clue constraints
3. Determine which cells must be empty and mark them with X
4. Repeat for all rows and columns, using information from one line to help solve others

The key insight: where groups must overlap regardless of their exact position, those cells can be filled with certainty.

---

Example: Basic Logic

Consider a 10-cell row with clue 7:

• A group of 7 must fit somewhere in 10 cells
• If placed at the leftmost position: cells 1-7 are filled
• If placed at the rightmost position: cells 4-10 are filled
• The overlap (cells 4-7) must be filled no matter where the group goes

This technique of finding overlaps is fundamental to solving nonograms.

---

Common Solving Techniques

Edge logic

When a clue starts with a large number, the first cells of that line often must be filled. Similarly for the end of lines.

Overlap analysis

Find cells that must be filled regardless of where groups are positioned within the line.

Counting spaces

If there aren't enough remaining empty cells to fit the remaining groups plus gaps, you can deduce more filled cells.

Cross-referencing

Use information from rows to help solve columns, and vice versa. A filled or crossed cell in one direction gives you information for the perpendicular line.

---

Difficulty Levels

Nonogram difficulty depends on:

• Grid size: Larger grids (15x15, 20x20) are generally harder
• Clue patterns: Some clue combinations allow more immediate deductions than others
• Picture complexity: More intricate pictures often require more careful reasoning

---

How a Nonogram Puzzle Ends

A nonogram is complete when:

• All cells are either filled or crossed
• Every row matches its clue exactly
• Every column matches its clue exactly
• The revealed pattern matches the intended picture

---

Using the Check Feature

If you're unsure about your progress, use the Check button:

• Correct cells are highlighted in green
• Incorrect cells are highlighted in red
• Checked cells become locked and cannot be changed

This helps you catch mistakes early without revealing the entire solution.

---

Summary

Nonogram is a game of logical deduction. By analyzing row and column clues, you determine which cells must be filled and which must be empty. Start with the largest clues and use overlap logic to make progress. Cross-reference between rows and columns, and mark empty cells with X to keep track of your reasoning. With practice, you'll reveal pictures with confidence.