What is hanjie and how do you play it?

Hanjie puzzles have been around for a long time, but they are still unknown to many puzzle players.

You may have played hanjie under a range of names - it has been known variously as tsunami, hanjie, nonogram, griddler and probably more besides.

The aim is to work out which cells in each row and column of the grid-based puzzle must be filled in. To help decide this, at the edge of each row and column are a series of numbers that tell you how many cells are filled in that region.

For instance, it could say ‘5,2′ - this means there are five filled cells and another region of two filled cels that are consecutive. A comma denotes a gap of at least one cell between filled regions (otherwise it would be 7 if there was no gap!), but the gap can be many more than one cell.

The puzzle is solved through cross-referencing, and making gradual progress each time through with the harder puzzles.

Some things are easy to work out - for instance if all or none of the cells in a row are to be filled then you can fill them in straight off. If more than half of the cells are to be filled, then you can fill the middle cell(s).

For instance, if the row is five cells in length and you know that 3 cells are filled, then in any combination the middle cell must be filled in, therefore you can fill it in.

Likewise, you can also make progress by working out cells that are not filled too, as this can further constrain options for the various regions and columns. To mark a cell that cannot be filled may hanjie players like to put a dot in the cell.

At the end of the puzzle you will reveal a simple black and white image, and a clue to this is often given at the start of the puzzle. Depending on how good the puzzle artwork is, the image may be more or less easy to recognise at the end!