As title, what i want to realize with Processing:

There are classical circles running across on the screen, then:

the first time you click the mouse,all the circles freeze(stop moving);

the second time you click the mouse, you draw a new circle with your mouse position.

Okay now is the problem: how to tell the computer to act differently? After all, they are all clicks, seem the same to the computer.

Does anybody know? Thank you very much.