Cumulative/asynchronous JS animation

I couldn't find a JS lib that came with parallel animation execution. I found lots of stuff with sequencing and callbacks, which is very good / snazzy / handy. But, I found myself needing an effect where an object can be influenced by multiple destinations at once.

When all the "pulls" have run their course, the element will eventually settle down.

For a while, some little pink boxes will indicate a "green box, please come this way" point.

After that, try moving your mouse around. Make some circle gestures. Notice that the green box doesn't exactly follow that path that your cursor takes, rather, it takes a sort of lazy-as-possible shortcut in catching up to it.

This demo probably doesn't work in IE.

Do let me know if there is someone else who did this already. I suspect there is, but my Google-fu is weak today, apparently.