Nonogram – Play Online for Free

A nonogram is a picture hidden behind numbers. Next to every row and above every column of the grid you see how long the blocks of filled squares are, and by combining these clues cleverly you paint a picture bit by bit. The idea comes from the Japanese graphic designer Non Ishida. In the late 1980s she won a competition in Tokyo in which pictures were made from the lit and dark office windows of a high-rise, in 1986 or 1987 depending on the source. She turned this into a puzzle on squared paper and published three such "Window Art Puzzles" in 1988. Around the same time the puzzle author Tetsuya Nishio hit on the same idea on his own.

The puzzle got its name in Britain. The puzzle collector James Dalgety put it together from Ishida's first name and the end of the word diagram, and from 1990 the Sunday Telegraph printed a grid every week. In 1998 the paper let its readers choose a new name, and they picked Griddlers®. Elsewhere the puzzles are called Hanjie or Picross®, short for "picture crossword," the name Nintendo used for Mario's Picross on the Game Boy in 1995; our Nonogram has no connection with Nintendo or with the owners of the Griddlers name. For mathematicians the puzzle is harder than it looks: deciding whether any given grid has a solution at all is NP-complete, as two computer scientists from Tokyo showed in 1996. Here you can play nonograms online for free, in three sizes and with no sign-up, and every new puzzle can be solved without guessing.

Count the Blocks, Mark the Crosses: Rules and Solving Methods for Nonogram

In the end every square is either filled or empty. Here is what the numbers mean and how our online nonogram works:

• The numbers: each number stands for a block of filled squares in a row, and the blocks come in the same order as their numbers, from left to right in rows and from top to bottom in columns. Between two blocks there is at least one empty square, and before and after them any number. If the edge shows only a 0, the whole row or column stays empty.
• Fill and Cross: one click fills a square, a second click empties it again. After a click on the "Cross" button, every click places a cross instead, a reminder that a square is sure to stay empty, and "Fill" switches back. With the right mouse button you can place a cross at any time, whichever button is active.
• Dragging: hold the mouse button or your finger down and move along a row or column to change many squares in one stroke. The stroke keeps the direction you first drag in and only changes squares that looked exactly like the first one, so you can pass over crosses without filling them.
• Keyboard: once the grid has been clicked or reached with the Tab key, the arrow keys step from one square to the next. Space or Enter fills, X places a cross, and pressing the same key again takes the mark away. Backspace or Delete clears a square.
• Help along the way: the row and column you are working in are highlighted, and so are their numbers. When the filled squares of a line match its numbers exactly, the numbers fade. When your squares and crosses leave no possible arrangement for that line, the numbers turn red.
• Check and Hint: "Check" colors wrongly filled squares and wrong crosses red and tells you how many there are. "Hint" reveals one square: the selected one if it is not right yet, otherwise the first open one in its row, its column or the whole puzzle. Revealed squares are shown in blue, locked in place, and included in the count at the end.
• Three sizes: on Easy the grid measures 5 × 5 squares, on Normal 10 × 10 and on Hard 15 × 15. A click on "New Puzzle" creates a fresh picture with exactly one solution, which you can work out from the rows and columns alone.
• Progress: the game keeps a grid of its own for each size, even after you close the browser. If you have already filled squares or set crosses, "New Puzzle" asks for a second click on "Sure?". Once everything is right, the picture turns green and the crosses disappear.

With these methods you will move forward line by line:

• Big blocks first: a long block overlaps with itself. A 7 in a row of ten squares starts in the fourth square at the latest and ends in the seventh at the earliest, so the four squares in between are filled for sure. In general, subtract all the blocks and their required gaps from the length of the line: every block longer than what is left has as many sure squares as it exceeds it by. With 4 3 in ten squares, two squares are free to move, so two squares of the four-block and one of the three-block are fixed.
• Lines filled to the brim: when blocks and gaps fill a line exactly, there is only one arrangement. A 10 or a 5 4 in ten squares is done at once, and on the small grid so is 2 2 or 1 1 1.
• Cross out zeros right away: a line with a 0 stays completely empty. Crossing it out at the start tells every crossing line what it needs to know at that spot.
• Think from the edge: if the first square of a row is filled, the row's first block starts there. If the first number is 3, the first three squares are filled and the fourth gets a cross.
• Crosses draw borders: a stretch between two crosses, or between a cross and the edge, that is shorter than every block of the line stays empty. If a row with the number 3 has a cross in its third square, the block does not fit into the first two, and they get crosses too.
• Close finished lines: when the numbers of a line fade, all its blocks are in place. Cross out the remaining squares so the lines across it know where they stand.
• Go back and forth between rows and columns: every new square and every cross tells the crossing line something, and often a single cross sets off a whole chain. The thick lines after every fifth square make counting easier.

Squares, Digits, Pictures: More Food for Logic Fans

If a nonogram leaves you wanting more grids and deduction, here is your next helping:

• Kakuro: numbers stand at the edge of the runs here too, only now you do arithmetic: each run's digits must reach a given sum, with no repeats.
• Minesweeper: the numbers here are not block lengths but the count of mines touching a square. Figuring out which squares are safe works almost like placing crosses.
• Sudoku: nine rows, nine columns and nine boxes, each holding every digit from 1 to 9 exactly once. Instead of a picture, rows of numbers emerge that limit one another.
• Sokoban: another puzzle from Japan. You push crates through a warehouse onto their targets, and one careless push can trap a crate for good.
• Falling Cubes: blocks on the move. Falling pieces want to be turned and dropped so they form gapless rows, which then vanish.