This is the best particles collision java applet i have ever seen.
800 particles and still not lag! it is incredible.
will study it carefully and add it here http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1455.msg5505#msg5505
Well done! credits to Francisco Esquembre and Fu-Kwun Hwang for this Best Brownian motion java applet  ;D