Wobblestone: an interactive rattleback (celt, wobble stone): a rigid body rolling without slipping on a plane, whose mass axes are skewed from its shape, so it spins happily one way and spontaneously reverses the other. Exact Newton-Euler dynamics with the contact force eliminated, an adaptive Dormand-Prince RK5(4) integrator, the instability growth rate recovered from the simulation itself, and an angular-momentum audit about the contact normal. Pure client side: no account, no network call, no credits. Independent reimplementation of a public-domain physical curiosity; named Wobblestone because RATTLEBACK is a registered trade mark; the register entries are reproduced verbatim in the app and no clearance is claimed.

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.