Make time-variation smoother

[ArthurGoodman]

I noticed that with t=sin(time) the variation of the art with time is kind of not ideal, because it just oscillates between two states.
To mitigate that the most natural solution seems to be to add a second time variable, that will change with cos, so I added s=cos(time).
With this instead of oscillating between two states, the art continuously rotates through the seamless set of states.
Quite a simple change, that significantly improves the aesthetics IMO :)

EDIT: As suggested by @adam-devel , I made t=time and added cos function. This allows to achieve the same result, but is more simple and flexible.

[ArthurGoodman]

Example:

output-scaled.mp4

[adam-devel]

Operations on time should be managed at the grammar level, it makes more sense to expose the raw time as t, then introduce sin(t) and cos(t) as terminal symbols alongside x and y etc..
This offloads the computation of these functions to the GPU, makes the source code simpler.

Otherwise you will have to edit the source code whenever you want to add another "timeline" so to say

[ArthurGoodman]

@adam-devel Oh yea, this makes a lot of sense. Thank you!