Oh I'm so ready for this.. I've had some success with Box2D in the past, it's well and truly one of the top bits of F/OSS out there.

Box3D-based Spectre VR? It's so happening. (Shades of Tanarus ..)

EDIT: holy smokes, the transition to recording and playback in the Legend of California demo (Unreal Engine-based) is quite a jarring leap. If you at first get the impression things are quite basic, be sure to get into at least 18:00 into the demo video, it gets pretty wild .. recording and playback is awesome.