So they work under IE 4.x, Netscape 4.x or higher . It will not work under IE 3.x nor Netscape 3.x. Works fine with IE on Windows NT and with Netscape on any platform.
System is composed of different classes.
There is a class ball, who's objects interact with each other. On reflect - Ball reflect from a cube surface. I respond to whose events implementing different system's behavior. For example in applets above I apply different physics lows. There is no restrictions and we can apply any lows, even if they don't exist in nature.