add vectorfield sketch

[hellochar]

centripetal force
directional sine force
radial sine force
flower force
atan force
a whole list of the above
ui for creating/deleting forces?
click to create radial sine force? click to create flower force? click to create centripetal?
click and drag to create directional sine force?
how to control power
how to delete forces
how to show forces exist in the first place?
maybe don't; just show their actions on the particles
a nice shader to go along with this