Simple Physics Engine for jMonkeyEngine

I'm currently developing an open-source multiplayer networked FPS engine, after getting addicted to Overwatch and TF2 and then wondering why there's not a single open-source Java multiplayer source game anywhere.  I aim to fix that, and at the moment progress is coming along nicely; it was never going to be easy but so far it has remained fun.  There's nothing to actually release yet; I'm going to wait until I've actually got a full game working before I release the source.

Anyhoo, the project has necessitated some additional code not directly linked to the project, which I can release.  The first one is a Simple Physics Library for jMonkeyEngine.

jMonkeyEngine comes with an excellent physics engine.  However, it is almost too excellent, and has a lot of features that I don't require which takes up CPU usage.  In addition, a multiplayer networked FPS requires the ability to "rewind" time on physical objects, which the existing JME physics engine can't do.

The full source is available here, which includes an example "first-person walking around" game.

And here is a video showing it in action.