Bubbles burst when they hit the walls or when they touch each other.

Multiple bubbles can be drawn and they blow up at the same rate simultaneously.

Some nasty bugs exist:

• if there are too many circles running sometimes the graphic cannot update fast enough and may leave behind some ghost circles around.
• IE users may not be able to see the circles. I don't know why. But there is no problem running this applet by using Netscape.