Which puzzle types are there?
- Classic 9 x 9.
- Sudoku X (diagonals).
- Jigsaw (irregular regions).
- Killer (cages and sums).
- Samurai (five grids).
- Thermo (rising thermometers).
- Arrow (sums along arrows).
- Giant 16 x 16.
- 6 x 6.
- 4 x 4.
- Kids: 4 x 4, then 6 x 6. A book holds one type. To publish two types, make two books (or a kids book, which climbs from 4 x 4 to 6 x 6 by itself).