Circles grow at a constant rate.

No two circles can overlap.

Bigger circle pushes and shrinks smaller circle when in contact.

A circle “pops” and makes a sound when its boundary intersects with the center of another circle.

The pitch of the sound is determined by the position of the circle on the background. Bigger the hole, higher the pitch.

The envelope of the produced sound is determined by a number of parameters including final circle size and time of interaction between two involved circles.