Nonogram (Picross)

Nonograms, also known as Picross, Griddlers, or Paint by Numbers, are picture logic puzzles where the player fills in cells on a grid to reveal a hidden image. Each row and column has a sequence of numbers indicating the lengths of consecutive filled blocks in that line, with at least one empty cell between each block. By cross-referencing the row and column clues, the player deduces which cells to fill and which to leave empty, gradually uncovering a pixel-art picture.

Rules

1. The grid starts completely empty.
2. Numbers at the left of each row describe the groups of consecutive filled cells in that row, from left to right.
3. Numbers at the top of each column describe the groups of consecutive filled cells in that column, from top to bottom.
4. Groups must appear in the given order and must be separated by at least one empty cell.
5. Cells are either filled or empty — there are no numbers placed inside the grid.
6. The completed puzzle reveals a picture.

Example

A row clue of "3 1 2" means: a block of 3 filled cells, then at least one empty cell, then 1 filled cell, then at least one empty cell, then 2 filled cells.

Strategies

• Full Lines: If the sum of clue numbers plus minimum gaps equals the row/column length, the entire line is determined. For example, clue "10" in a 10-cell row means all cells are filled.
• Overlap (Glue): For a clue in a line of length L, calculate where the block could start at its leftmost and rightmost positions. Cells that are filled in both positions can be confirmed. For example, clue "7" in a 10-cell row: leftmost fills cells 1-7, rightmost fills cells 4-10 — cells 4-7 are certainly filled.
• Edge Logic: If a filled cell is adjacent to the edge (or a confirmed empty cell), the block starting there must have a specific length, allowing more cells to be filled or marked empty.
• Gaps Too Small: If a gap between confirmed empty cells is too small to fit any remaining block, the entire gap can be marked empty.
• Completed Groups: Once a group reaches its full length, the cells on either side can be marked empty.
• Marking Empty Cells: Actively mark cells you know are empty (usually with an X or dot) — this is as important as filling cells.

Nonograms were independently invented by two people in the same year. In 1987, Non Ishida, a Japanese graphics editor, won a competition in Tokyo by designing grid pictures using skyscraper lights that were turned on or off. She published the first puzzles under the name "Window Art Puzzles" in 1988.

Also in 1988, Tetsuya Nishio, a Japanese puzzle author, independently created the same type of puzzle. He called them "Paint by Numbers" and began publishing them in puzzle magazines.

The puzzle gained international fame when The Sunday Telegraph in London began publishing them in 1990 under the name "Nonograms," a portmanteau of "Non" (from Non Ishida) and "gram." The newspaper ran a competition that attracted enormous reader interest.

In 1995, Nintendo released "Mario's Picross" for the Game Boy, introducing the puzzle to millions of gamers worldwide under the name "Picross" (picture crossword). The game was hugely successful in Japan and spawned a long-running franchise that continues today, with titles for DS, 3DS, and Switch. The Picross series by Jupiter Corporation has become particularly popular, with "Picross S" games regularly releasing on Nintendo Switch.

The format has expanded to include color nonograms (where cells can be different colors, reducing ambiguity), triddlers (triangular grids), and massive nonograms with grids of 100x100 or larger. Online communities like nonograms.org host thousands of user-created puzzles.

Nonograms are beloved for their unique reward: unlike most logic puzzles, solving one produces a recognizable picture, giving the solver a visual payoff beyond the satisfaction of logical deduction.