🖼️ Nonogram

How this Nonogram works, square by square

Pick a size at the top: 5×5, 10×10 or 15×15. Every row has a clue on its left and every column has a clue above it. Each number is one unbroken run of filled squares, listed in order, with at least one empty square between runs. A row clue of 2 1 means two filled squares, then a gap of one or more, then one filled square. A clue of 0 means the whole line is empty.

You switch between two tools under the board. Fill (■) commits a square, and the game checks it on the spot. Mark (✕) drops a cross where you think a square is blank, and it is never checked, so you can tap it again to take it back. You win the moment every square of the picture is filled. You don’t have to cross out the blanks first; marks are just your notes.

There’s no timer and no hint button. The only pressure is the ⚠ counter in the top bar: three wrong fills and the puzzle is lost.

Worked example: the slack method

The single most useful trick in any Nonogram is counting slack. Add up the clue numbers, add one for each gap between them, and subtract that total from the line length. What’s left is the slack: how far the runs can slide. Any run longer than the slack has certain squares, exactly run minus slack of them.

Take a 10-wide row with the clue 3 4. Minimum length is 3 + 1 + 4 = 8, so slack is 2. Push everything left and the 3 covers squares 1 to 3; push it right and it covers 3 to 5. Square 3 is filled either way. The 4 covers 5 to 8 at the far left and 7 to 10 at the far right, so squares 7 and 8 are certain.

Slack of zero means the line is fully solved. On 5×5 that happens a lot: 5, 1 1 1, 2 2, 3 1 and 1 3 all have zero slack, so you can fill them straight away and cross out the gaps.

Fill, Mark and what a mistake really costs

Correct fills lock in place and can’t be undone. A wrong fill adds one to the ⚠ counter, and the game turns that square into a cross for you.

That last detail matters. A mistake isn’t pure loss: it tells you for certain that square is blank, which can unlock the row and column through it. Leave that cross alone: it is an ordinary mark, so tapping it again in Fill mode counts as another mistake. Still, the safe habit is to sit in Mark mode while you work out blanks, and switch to Fill only when a square is certain. Every new puzzle starts in Fill mode, so check which button is lit before your first tap.

Beginner mistakes to stop making

Most lost puzzles on this board come from a handful of habits, not from hard logic.

• Reading 2 1 as twenty-one, or as a 3. Each number is its own run, and order matters: 2 1 puts the pair before the single.
• Forgetting the gap. Two runs in one line always need at least one blank between them, which is why 3 4 needs 8 squares, not 7.
• Never marking blanks. Crosses shrink the space a run can slide in, and that creates new overlaps.
• Ignoring finished lines. When a row’s runs are all filled, cross out everything else in it immediately. Those crosses feed every column they touch.
• Tapping in the wrong mode. Most lost puzzles come from a fill meant as a mark, not from bad logic.

Intermediate and advanced moves

Work the edges. A filled square touching the border must be the start of the first run (or the end of the last). If a row clue begins with 3 and square 1 is filled, squares 2 and 3 are filled too and square 4 is blank.

Use reach. If a row clue is a single 2 and you already have square 6 filled, the run can only touch squares 5 to 7, so everything else in that row is blank.

On 10×10 and 15×15, the thicker grid lines split the board every five squares. Use them to count without losing your place.

Ping-pong between rows and columns. Each new fill or cross changes the slack of the crossing line, so after any progress, re-check the lines it touches before hunting elsewhere.

Choosing your size

The game generates a fresh random picture each time, with about half of its squares filled, so boards are busy rather than sparse. Dense lines have big clues and little slack, which means lots of overlap fills.

5×5 is a two-minute warm-up and the best place to learn zero-slack lines. 10×10 is where the slack method and edge work really start earning. 15×15 rewards patience and careful counting, and one miscount can cost a life. Your choice of size is remembered, and an unfinished puzzle is saved if you leave, as long as you come back to the same size. Switching size or pressing ↻ deals a new puzzle.

Where Nonograms came from

The puzzle took off in Japan in the late 1980s, credited to two independent creators, Non Ishida and Tetsuya Nishio. The English name nonogram comes from Ishida’s first name. Nintendo later popularised it as Picross, short for picture crossword, and you’ll also see it sold as Hanjie, Griddlers and Paint by Numbers.

Nonogram FAQ