Diffusion Simulator

A simulator that lets circular "particles" bounce around, while demonstrating how diffusion works. I made this app because I couldn't visualize osmosis, and I was trying to confirm my understanding of diffusion. From my understanding, diffusion is due to the difference in probability of collision, which is quite easy to visualize. However, I couldn't for the life of me understand osmosis. The app doesn't help, there was no clear pattern in osmosis. Perhaps my model is too simplified. However it demonstrate diffusion quite well. Control: tap and hold anywhere on screen to concentrate particles. Other than that, just observe what happens.