The AcrossLite format is not publicly documented. This specification was built by probing dozens of `puz` files and is a living document that will be update as new sections of the format are figured out.
## Format
The `puz` file format is a binary blob with `latin1` encoding.
### Header
The header section is consistently 52 bytes long.
|Label|Start offset|Length (bytes)|Notes|
|:----|:----|:----|:----|
|Puzzle width|`0x2c`|1|Self-explanatory.|
|Puzzle height|`0x2d`|1|Self-explanatory.|
### Body
The body of the puzzle starts consistently at offset `0x34`.
|Label|Start offset|Length (bytes)|Notes|
|:----|:----|:----|:----|
|Solution|`0x34`|`width * height`|Based on the height and width, the solution is written out as ASCII.|
|Layout|(end of the solution)|`width * height`|The layout of the grid is defined with `.` used as "empty cell"|
|Clues|(end of the layout)|???|`NUL` separated strings containing each of the clues, not numbered.|
The file doesn't contain information in which cells correspond to across and down clues. This information can be derived from the puzzle layout and the set of clues available:
```
FOREACH cell IN grid:
IF cell has a non-empty top neighbour
THEN the cell is part of its top neighbour's down word
ELSE the cell is part of the next available down word
IF cell as a non-empty left neighbour
THEN the cell is part of its left neighbour's across word
ELSE the cell is part of the next available across word
```
By picking off clues from the across and down clue lists, assigning them using the algorithm above and numbering them as you go, you can build the correct cell <> clue mappings.
