Algodoo

Perpetual motion machine test. Outer magnets push inner ones which in turn try to "get together".

The engine require initial push, but then runs for quite long while. With alteration to the design such
as different amounts of magnets or different placing even more runtime can be achieved or even
perpetual motion.

If I were to prototype it in real life, I'd used strongest neodymium magnets I could find and custom 3d printed "shell" from non-ferromagnetic material,
including axis for inner magnets.
The engine is top-down. If someone prototype it IRL and it works, he'll be rich. I don't have time or money to do this on my own, maybe you have?