I really love the physics and sandbox of this. It was a lot more comfortable and satisfying to observe than I expected.
My only suggestion would be having some kind of satisfying sound when everything collides together, like a well-recorded sound of two marbles clicking together, or something like that? It would be very audibly pleasant each time you regen the whole thing to hear them colliding like that.
Very nice work and I hope you add a little extra to it later. It's awesome!