Novem
Nine by nine, solved by logic.
What it is
Novem is a pure Sudoku engine: it solves by constraint propagation (naked and hidden singles) backed by minimum-remaining-values backtracking, counts solutions to guarantee a unique puzzle, generates boards by hole-digging, and explains its hints step by step. 14 tests keep the logic honest. A from-scratch, dependency-light build you can download and run locally.
A pure Sudoku engine: constraint propagation (naked/hidden singles) + minimum-remaining-values backtracking, solution counting for uniqueness, hole-digging generation, and explained hints. 14 tests.
What's inside
The full source, the tests, and CI. Open it, read it, change it. A zero-dependency core, free, in the MIT spirit.
Run it after unzip
pnpm install && pnpm dev