Actually, it is just the theme of the game, and it has nothing to do with the real experiment. Particle collisions will make their directions and speeds change randomly, rather than real physical collisions.
I once wanted to try to reproduce the real collision, but as the number of particles increased, the amount of calculation required also became larger and larger. This caused the game to be unable to run smoothly, and in the end I had to give up the plan. 😕