Or use Foam, precompse it, and time reverse the precomp.
the hardest thing about particle systems running backwards is that the physics that are built into them are designed to simulate explosions, not gatherings.
I have zero experience with Particle Playground but I’ve gotten great reversals with Foam, CC Particle Systems, and CC Particle World. World is probably my favorite because the floor can be edited to be a wall or ceiling and have bounce properties.
Someday I simply MUST explore Palyground.
bogiesan