Nonograms (Griddlers) Puzzle

Nonograms are picture logic puzzles. They are also called Griddlers, Paint by Numbers and Hanjie. Each row and column has a list of numbers, and those numbers tell you how the filled cells are grouped in that line. Fill in the right cells and a hidden picture appears. You can play grids from 5×5 up to 20×20, and every puzzle here has exactly one solution that you can reach by logic, with no guessing.

Rules

The grid starts empty. The clues sit to the left of each row and above each column.

Each number is a block of that many filled cells in a row, with no gaps. In a row, the blocks are read from left to right; in a column, from top to bottom. They appear in the same order as the numbers.

Two blocks in the same line are separated by at least one empty cell. There can be empty cells before the first block and after the last one too.

A line with no numbers has no filled cells at all.

The puzzle is solved when every row and every column matches its clues.

Controls

Tap a cell to fill it. Drag along a row or a column to fill several cells in one go; the stroke snaps to the line you started in, and a small bubble counts the cells as you drag. Tap a filled cell again to clear it.

Crosses mark cells you know are empty. Pick Cross under the board, and taps and drags place crosses instead. With a mouse you don’t need to switch: left-drag fills and right-drag crosses. The first cell of a stroke decides what it does, so a stroke that starts on a cell that already has that mark clears instead.

On a keyboard, the arrow keys move around the grid. Space, Enter or F fills the cell, X crosses it, and Backspace, Delete or 0 clears it. The current row and column, and their clues, are highlighted as you move.

Auto-cross is on by default: when a fill brings a row or column up to the total of its clues, the rest of that line is crossed for you, in the same undo step. Turn it off under the board if you prefer to cross cells yourself.

A clue number turns gray once its block is pinned in place and painted, and a whole line’s clues turn gray once that line is finished. If a row or column can no longer fit its clues, its clues and outline turn red. Press Hint for a cell the clues already force, with the reason behind it. Press Check when you want the board scored against the rules. Undo and Redo step through your moves, and Reset clears the grid.

Beginner tips

Start with big numbers. In a row of 10, a block of 7 has only 3 cells of room to slide, so wherever it goes, cells 4 to 7 are filled. The same overlap works for several numbers: add them up with one gap between each, and compare that with the length of the line.

A clue that fills the whole line, like 10 in a 10-wide row or 4 1 3 in a row of 10 (4 + 1 + 3 plus two gaps is exactly 10), has only one way to fit. Fill it straight away.

Use crosses. Once a line has all its blocks, cross the rest. A crossed cell splits a line into shorter pieces, and a short piece that is too small for any block left must be empty.

Work back and forth. Every cell you fill or cross in a row is new information for the column it sits in, so after each line, look at the lines that cross it. Easy grids fall to these ideas. Medium and hard grids make you keep track of where each block could still go, and combine rows and columns more often.