Click me to start/stop animation.
Click me to toggle tails.
Click me to toggle collision detecting.
Click and drag the circles to move them.

This demo was made by Zachary Johnson. Please come visit my blog about web development, video games, and other geek topics: zachstronaut.com.

The more complex mode requires an optimized JavaScript engine such as the one found in Safari 4 or Firefox 3.1.
Other browsers that support canvas should stick with the original mode.