Reading the github page, though, this is really about tweening with no mention of interruption. However, using Verlet (not Newtonian like rebound-js!) you can easily combine both approaches since Verlet allows you to mess with a position directly (velocity is implicit in position deltas, so really stable although less accurate).

I wrote a rejected paper about this a few years ago; it might be useful as a reference:

http://research.microsoft.com/pubs/191705/uiphysics09.pdf

I wrote that when I was doing a lot of work with WPF, whose animation/data binding system is fairly similar to what is being explored in Javascript today (with frameworks like React). But beyond data binding and canned animations, I think physics is the next step.

Re: interruption, from the docs:

> stackBehavior (default: tweenState.stackBehavior.ADDITIVE). Subsequent tweening to the same state value will be stacked (added together). This gives a smooth tweening effect that is iOS 8's new default... The other option is tweenState.stackBehavior.DESTRUCTIVE, which replaces all current animations of that state value by this new one.

So DESTRUCTIVE is what allows interruption.

This is not much different from WPF's animation support, and I don't think it really helps. The interruptions are still not very natural looking. It was definitely useless for Surface (the table, not the tablet) when I was doing UX prototypes for it.

Additive is a better "interruption" in a lot of cases from what I've seen. Destructive was added after the fact for completeness. What do you think?

I would love to chat with you about what you've learned working on this stuff. If you're interested, drop me an email at floydophone at gmail dot com