The numbers along the top and down the side tell you which squares are filled. Work out which ones and a picture appears.
Nothing is guessed. Every square can be reasoned out from the clues, and the puzzle tells you when the picture is complete.
Each clue is a run of filled squares in that row or column, in order, with at least one gap between runs. A row clued 3 1 has three filled squares, a gap, then one more.
Left click or tap fills a square. Right click, or the second tap, marks it with a cross to say you have ruled it out. Dragging works for both.
Crosses matter as much as fills. Ruling squares out is usually what makes the next run obvious.
Start with the biggest clues. In a ten wide row, a run of eight has to cover the middle six squares no matter where it sits, and those squares are free information.
Each number is an unbroken run of filled squares in that line, listed in the order they appear, with at least one empty square between runs.
No. Every puzzle here can be finished by reasoning alone, so being stuck means there is a deduction nearby rather than a coin to flip.
It marks a square you know is empty. It changes nothing in the puzzle itself, but it keeps your reasoning visible and stops you counting the same square twice.
From five by five up to twenty by twenty. The small ones take a minute, the big ones are an evening.
Nonograms go by several names, including Picross and Griddlers, and they all work the same way: numbers describing a picture you have to reconstruct.
The technique that unlocks most puzzles is overlap. Slide a run to the far left of its line, then to the far right, and any square covered both times is filled whatever happens in between.
Finishing one is a good feeling precisely because the picture is hidden until near the end, when a shape suddenly resolves out of the squares you were treating as pure logic.