Neat visualiser, although I'd like to see the value dot moving from left to right (feels more natural to observe the motion like that, since that's what we usually see in everyday life).
Now, how about adding and visualising custom spring equations? Both http://bouncejs.com/ and http://framerjs.com/ use spring equations (in fact, even two various implementations – DHO and RK4 – https://github.com/koenbok/Framer/tree/master/framer/Animators) and as far as my memory goes, AS3 version of GSAP had CustomEquation class that was based off Beziér's curves.
I've started using GSAP again after a while (for CoffeeScript based prototypes) and it's awesome, and it has the most clean docs too. Would be nice to see spring equations showing up in the next release – but no pressure Jack ;-) Thanks!