[quote author=lookang link=topic=1186.msg4649#msg4649 date=1251859495]
http://www.um.es/fem/EjsWiki/Main/ExamplesMultipleCollisions by Francisco Esquembre is possibly a suitable example for u to study and discuss on.

[/quote]
I check your code when there are some overlap, you ask the program to give the ball a new random velocity. it is right?