How to solve nonograms

A nonogram is a picture hidden in a grid. Numbers beside each row and above each column tell you which squares to fill. Fill the right ones and a little picture appears. There is no guessing: every puzzle can be solved by logic alone, one square at a time. You can practise everything in this guide in Pixel Nono.

What the numbers mean

Each number is a run of filled squares in that row or column. The clue “3 1” means: somewhere in this row there are three filled squares side by side, then at least one empty square, then one more filled square. The runs always come in the order written, from left to right (or top to bottom), and there is always at least one empty square between two runs. A clue of “0”, or no number at all, means the whole line stays empty.

Start with the easy lines

Look for lines you can fill completely. In a row of 10 squares, a clue of “10” fills the whole row. A clue of “4 5” also fills it exactly: four squares, one gap, five squares — 4 + 1 + 5 = 10. Add up the numbers plus one gap between each pair; if the total equals the length of the line, you know every square.

The overlap trick

This is the most useful idea in nonograms. Imagine a row of 10 squares with the clue “7”. Push the run of seven as far left as it can go: it covers squares 1 to 7. Now push it as far right as it can go: squares 4 to 10. Squares 4, 5, 6 and 7 are filled in both cases — so they must be filled, wherever the run really sits. Whenever a run is longer than half of the free space, its middle part is certain. The same trick works with several runs in one line: place them all as far left as possible, then as far right, and fill every square that the same run covers both times.

Mark the empty squares

Knowing which squares are empty is just as important as knowing which are filled. When a line is complete, cross out the remaining squares — in Pixel Nono, switch to Mark mode and tap them. Marks stop you from filling a square by mistake and, more importantly, they make the other lines easier: an empty square in a column may be exactly what tells you where a run in a row must go.

Use the edges

If the first square of a row is filled and the first clue is “3”, the next two squares are filled too, and the square after them is empty. Filled squares near an edge are strong clues because the run cannot extend past the border.

Switch between rows and columns

Solving a nonogram is a conversation between rows and columns. Each new filled or marked square in a row gives information to the column it sits in. When you get stuck in the rows, go through the columns one by one, and the other way round. Most puzzles are solved by many small steps, not by one big discovery.

When you are stuck

• Re-check the lines that are almost complete: count the filled squares against the clue.
• Look for runs that are already placed and mark the squares around them as empty.
• Try the overlap trick again on lines that have changed since you last looked at them.
• Take a short break. A fresh look often finds the step you missed.

Choose the right size

Small grids are perfect for learning: the logic is the same, but you see the whole picture at once. When the small ones feel easy, move to larger boards, where the techniques above really shine. Pixel Nono offers quick mini grids and large boards, plus a daily puzzle when you want a new challenge every day.

Ready? Play Pixel Nono and watch your first picture appear.