A nonogram (also called picross, griddlers, hanjie, or Japanese crossword) is a logic puzzle played on a grid. Your goal is to figure out which cells to fill and which to leave empty, using only the number clues.
The puzzle is a grid of empty cells. Common sizes are 5×5 (beginner), 10×10 (classic), 15×15 (advanced), and 20×20 (expert). Every cell is either filled (black) or empty (white).
Each row and column has a set of numbers. These numbers tell you how many consecutive filled cells appear in that line, and in what order. For example, a clue of "3 1" means there's a group of 3 filled cells, then at least one empty cell, then 1 filled cell.
Start with the rows and columns that have the largest clues — these give you the most information. If a clue takes up most of the line, you can determine some cells immediately by overlap logic. Cross out cells you know are empty to help track your progress.
You win when every cell that should be filled is filled, and no cell that should be empty is filled. The crossed cells don't matter for winning — only the filled cells need to match the solution exactly.