How does a nonogram work?

The rules of a nonogram

Each row and column has a clue. Every number in a clue is an unbroken run of filled cells, listed in order, with at least one empty cell between runs. A clue of 3 1 means a run of three, a gap of one or more, then a single cell.

Fill the cells the clues force and cross off the cells that must stay empty. The puzzle is done when every row and column matches its clue, and the filled cells are the picture.

How to solve a nonogram step by step

Work one line at a time, then let each new mark help the lines it crosses.

• Start with the overlap. Add the clue numbers plus one gap between each, then subtract from the line length. On a 10-cell line a clue of 7 has a slack of 3, so the middle four cells must be filled.
• Cross off what cannot fit. Gaps shorter than the smallest remaining run are empty, and so is the space beyond a finished run.
• Alternate rows and columns. Each new fill or cross gives the lines it touches new information, so sweep the rows, then the columns, and repeat.
• Do not guess. A well-made nonogram has a single solution that logic alone reaches, so there is always a next forced cell.

What Twinlatch adds: twin clues

Twinlatch is a nonogram with one extra rule. Some boards latch two neighbouring rows together, and a twin clue is one number drawn across both rows. It counts a single filled shape that touches both rows, joined edge to edge and never diagonally; every other number in those rows is an ordinary run.

Neither latched row can be solved alone. A twin number of 20 on a 10-wide board means both rows are completely full. Column clues read the ordinary way, so they are often the fastest way into a latched pair.

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Twinlatch has 107 pictures on 5×5, 10×10 and 15×15 boards, a Daily everyone shares, unlimited hints and no ads, lives or energy. The tutorial, today's ranked Daily and the first 26 pictures are free, with three practice boards a day.

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