This really should be self-explanatory.
Set the values, hit the button, and enjoy the show.
Rinse and repeat as necessary.
In time, more to follow...
Color of Circles (sorry, no rainbow)
Launching Pattern for Circles
Static Center
No
Yes
Bounce or Circle Shooter
Shooting Circles
Bounce
Number of Circles
Rate of Increase (Scale Factor)
Start Size Factor (Radius of Initial Circles)
Slow Down Factor (Higher makes it go slower)
Rotation Speed (in degrees, more or less)
Center Offset (distance from center circles originate)
Number of Cycles (before pattern repeats)
Tested in Mozzilla Firefox.
There is a minimum of validation, so I expect this is easy to break.
Still, if you limit yourself to positive numbers, it should work reasonably well.