Editorial policy
How we check every puzzle
We create the puzzles, verify them with a separate solver, and check the finished book and website before release.
- 01
Create each puzzle for its level
We build 9 × 9 Sudoku sets for Easy, Medium, and Hard, with a defined technique range for each level.
- 02
Verify independently
A separate solver checks that each puzzle has exactly one solution. A second check tests the solving techniques promised for its level: singles for Easy, locked candidates and pairs for Medium, and triples and X-Wings for Hard.
- 03
Review the assembled product
We check puzzle labels, answers, page order, and exported book files. The website has nine free puzzles at each level. They are separate from the puzzles in the books.
- 04
Publish corrections clearly
We list every confirmed correction on the Help page by book and puzzle number.
What we do not claim
We test puzzles and solutions. We do not make claims about brain training, health, intelligence, or guaranteed learning results. If a printed copy has a problem, the Help page explains what to report.