Thought I recognised that image @HS_Kim!
It might be easier to think about how combine the information from two points rather than use closest point, which then often gives rise to the hard transition you’re trying to avoid @samuel.ryu. For example, you could take the distances for all attractors, and then ‘reward’ those points that are close by (using an inverse power law or something, see attached) - then you will get a smooth transition as you move close to a particular attractor.
You can then use this resultant number to do something, rotate a circle, scale it, whatever. Keeping it to 2D just simplifies the whole setup in my humble opinion, but you could convert this number to a vector direction/magnitude if desired. Anyway, here is an example which is kind of similar to the right hand side of your original image example (just inverted).
Granted it’s not exactly the same, but hopefully it will lead you in the right direction.