Hi Jens,

I've attached below the old manual with the animations

Hopefully that is useful. 

In terms of other references, the standard one is Baraff & Witkin

There's lots of other good sources out there too

for example this nice elementary intro from Khan academy on Hooke's law

or the chapter on Forces in Daniel Shiffman's Nature of Code

Getting the most basic springs working can be surprisingly simple and fun, and I'd certainly encourage anyone to have a go at it to gain a better understanding of the principles. I learned about Newton's laws of motion and Hooke's law in school but it wasn't until I actually wrote them into some code and had that magic moment of seeing physically plausible behaviour emerge from those few equations that I felt I really appreciated their elegance and power.

However, going further with physics simulation and dealing with issues of numerical stability, material properties, system topology etc can get much more involved and time consuming. For this reason I'm working on making Kangaroo physics a more accessible library (working along similar lines as TraerPhysics, Box2D, or ToxicLibs), because I think there are many people interested in scripting physical behaviours who have a general understanding of the ideas involved, but don't necessarily want to have to rewrite all of this stuff from scratch.

(especially if they are more interested in doing something with the physics, such as combining it with a GA)

It would be interesting to hear if you think such a library would be useful, and how you'd want to use it...