The counterfeit-coin balance puzzle, playable in five variants, with an exhaustive decision-tree search that settles how many coins each number of weighings can handle and why the classic twelve sits one short of its own counting bound. Independent reimplementation of a public-domain puzzle; runs entirely in the browser with no model and no credits.

Every public app is built from a security-scanned skill and must pass a clean scan — skill and frontend — before it can be listed. Have a skill of your own? Turn it into an app — or read the step-by-step walkthrough.