Yes, the “air friction” is just there to get a stable proces (wich remains within limits). It turns out, that there is a precise value of the “Cd” coefficient for each combination of body masses and spring constants. I deliberately used V in stead of V^2, because the friction must always be counter directional to the velocity V, and in V^2, the direction sign (+ or -) is lost.
I tried the graph method you mentioned, and it workes fine and very simple.
A statement like n+=1 is short hand for n=n+1. Is also possible with -=, *=, &=, and so on.
(see documentation under “Basics/Expressions”)
A period just before a varable name indicates a “scope variable”.
Exemple: the variable “fun.act” is the variable “act” which is created in the function “fun”.
Everywhere in the entire program, the value of that variable may be retrieved or be set under that name.
If there is no function name before the period, the variable exists in the main program module.
(see documentation under “Basic/Functions” and “Basic/Scope variables”. Highly recommended reading

