How to play
- Choose an empty cell and inspect its row, column, and box.
- Enter a digit only when it does not duplicate another digit in those regions.
- Use elimination and candidate notes until the full grid is valid.
What this game practices
A strong constraint-solving game, although the digits act as symbols rather than quantities. It develops deduction more directly than arithmetic.
How we checked it
Open-source HTML5 game reviewed in the local coolmath build for startup, primary controls, restart flow, narrow-screen fit, console errors, failed requests, and third-party network activity. Upstream telemetry is disabled in this self-hosted copy.
Open-source license and attribution
This self-hosted game is adapted from Web Games by mashukui and distributed under the MIT License. coolmath disabled upstream telemetry and records its local changes in the open-source notices.
Reviewed by coolmath Editorial Team · Updated 2026-10-09