Nonogram — Play Free Online

What the numbers mean

Each row and column carries a list of numbers. They are the lengths of the runs of filled squares in that line, in order, with at least one blank between consecutive runs. A row marked "4 2" has a block of four, then at least one gap, then a block of two — somewhere in the row, in that order.

That is the whole ruleset. The picture at the end is a reward, not a hint; solving by guessing what the image might be is how people get stuck.

Start with the lines that cannot move

• A clue whose numbers plus the mandatory gaps exactly fill the line has only one arrangement. Fill it completely and immediately.
• Overlap: for a long run in a shorter line, slide it as far left as it goes, then as far right, and fill whatever squares are covered both times. This works even when you do not know where the run starts.
• Mark blanks. An X on a square you have proved empty is worth as much as a filled square — most deductions come from knowing where something cannot be.

Working the edges

Edges are where certainty lives. If the first square of a row is filled and the first clue is 3, the next two are filled and the fourth is blank. If the first clue is 3 and the third square is blank, the run has to start at square four or later.

Alternate between rows and columns constantly. A single square resolved in a row often forces two or three in the column that crosses it, and that cascade is the actual solving loop.

When you are stuck

Re-scan the longest clues first — they constrain the most and are the easiest to overlook once the board is half full. Then look for lines you have partially filled and recount them; a miscount is far more common than a genuinely unsolvable position.

If a puzzle really does need a guess, it is a badly generated puzzle rather than a hard one.