Numfield

Numfield is sudoku against the clock, in your browser. Four difficulty levels, a daily puzzle, season leaderboards, and links to share a puzzle and compare times with a friend. It works on phones too, and you can add it to your home screen. Fair play is at its core: the solution lives only on the server, which checks every digit, and each run is recorded as a log that can be replayed, so results can be verified. Technically it is a shared, deterministic TypeScript rules core, a Fastify server on PostgreSQL and Redis, a light framework-free Vite client, and an admin site for moderation and planned maintenance. It is versioned, with an update log inside the game.