How to Play Nonocross

The rules in 30 seconds

• Every row has numbers on its left, and every column has numbers on top.
• Each number is a block of filled cells in that line, in the same order as the numbers.
• Blocks are separated by at least one empty cell.
• A 0 means the whole line is empty.
• The puzzle is solved when every row and column matches its numbers.

How to read a clue

A row with the clue 3 1 in a grid six cells wide holds a block of three filled cells, then at least one empty cell, then a single filled cell. The blocks never change order, but the gaps can be wider.

Technique 1: Full lines

Add the clue numbers plus one gap between each block. If the total equals the line length, there is only one way to place the blocks, so you can fill the line straight away.

Technique 2: The overlap

When a block is longer than half its line, part of it must cover the middle. Imagine the block pushed as far left as it goes, then as far right. The cells it covers both times are always filled.

Technique 3: Empty and finished lines

A 0 means every cell in the line is empty, so cross it out. And once a line has all of its blocks placed, cross out every other cell in it. Those crosses are clues for the lines going the other way.

Technique 4: Start from the edges

A filled cell touching the edge of the grid must belong to the first block of that line. If the first clue is 3 and the first cell is filled, the first three cells are filled and the fourth is empty.

Technique 5: Cross-check every cell

Every cell sits in one row and one column. When a row step fills a cell, look at that cell's column straight away; often it completes a clue or creates a new overlap. Solving Nonocross is mostly this back-and-forth.

Worked example: a 5x5 grid

Here is Level 5 solved with the techniques above, one step at a time:

1. Step 1: Row 2 - the clue 5 fills the whole line. (5 filled)
2. Step 2: Row 3 - the clue 5 fills the whole line. (5 filled)
3. Step 3: Row 4 - the clue 5 fills the whole line. (5 filled)
4. Step 4: Row 1 - the clue 3 leaves only 2 free cells, so the middle of each long block must be filled. (1 filled)
5. Step 5: Row 5 - the clue 3 leaves only 2 free cells, so the middle of each long block must be filled. (1 filled)
6. Step 6: Column 1 - every block of 3 is already placed, so the remaining cells are empty. (2 crossed out)

Open the level page to see the remaining steps and the finished picture.

Fill or cross: use both marks

Nonocross gives you a fill mark and a cross mark. Use the cross for every cell you know is empty. Players who only fill tend to get stuck, because the empty cells are what make the next line solvable.

When you are stuck

• Scan every row and column once more for a full line or an overlap you skipped.
• Count the cells left in a line against the blocks still to place.
• Open your level and press Show next step for a single nudge.

Practice levels

Start with Level 1, a 3x3 warm-up, then try the first 10x10 grid in Level 33 once the techniques feel natural.

Nonocross rules: quick answers