My understanding is probably also incorrect / incomplete, but I use the "trampoline" mental model where objects on the medium both update and react too the loca

My understanding is probably also incorrect / incomplete, but I use the "trampoline" mental model where objects on the medium both update and react too the local geometry, ex. a tennis ball will roll towards the bowling ball, but doesn't "know" about the bowling ball. Though it begs the question _how_ a given particle has read/write privileges with the geometry.