How to Play Nonogram

What is a Nonogram?

A Nonogram (also known as Picross, Griddlers or Hanjie) is a picture logic puzzle. Each row and column has a clue listing the lengths of its runs of filled cells, in order. Fill the right cells and a hidden pattern appears. Every puzzle here can be solved by logic alone, with no guessing.

Reading the clues

A clue of 3 1 means a run of three filled cells, then at least one empty cell, then a single filled cell, in that order.
Runs are separated by at least one empty cell. The gaps can be longer.
A clue of 0 means the whole line is empty.
You win when every row and column clue is satisfied. Crosses are notes for you and never count.

Controls

Fill or Cross toggle chooses the tool. Fill marks a cell as part of the picture; Cross marks it as definitely empty.
Tap or click a cell to apply the tool. Tapping again with the same tool clears it. Filling over a cross replaces the cross, and a single undo restores it.
Drag across cells to paint a whole run. The first cell decides whether the stroke paints or erases, and the stroke locks to that row or column so it cannot smear diagonally.
Right-click or right-drag always uses the Cross tool.
Keyboard: arrow keys move, Space or Enter fills, X crosses, Z or Ctrl/Cmd + Z undoes, H asks for a hint and Escape deselects.
Hint fills or crosses one cell that the clues already determine and highlights the line it used. If a hint reports a contradiction, one of your marks conflicts with the clues.
Show mistakes flags any filled cell that is not part of the picture. Mistakes are counted even if you undo them.

Difficulty Levels

Easy — 5×5 grid. Short clues that resolve in a few passes.
Medium — 10×10 grid. Longer runs and more overlap reasoning.
Hard — 15×15 grid. Up to eight clue numbers on a line.

Techniques

Overlap: push a run as far left as it can go, then as far right. The cells it covers both times must be filled. A clue of 8 on a 10-wide line fills the middle six cells straight away.
Crossing off: once a line's clue is fully placed, cross every other cell so later deductions in the crossing lines get easier.
Edges: a filled cell touching the edge of the grid, or a cross, forces the run next to it to extend inward.
Too small to fit: a gap shorter than the smallest remaining run can be crossed out.

Tips

Start with the longest clues and the lines with the most numbers.
Alternate between rows and columns; each solved cell unlocks the crossing line.
Crossed-out cells are as valuable as filled ones. Use them generously.
A satisfied clue dims, so you can see at a glance which lines are done.