The demo applet consists in a wall made of balls without energy on which a ball is launched. The number of balls columns (initially 5) and the initial energy of the ball (initially 1; it may vary from 1 to 5) can be changed before start.
The number of energy transfers during one instant is not fixed and it depends on the geometry of the target. Thus the number of generated events is changing accross instants, which is not a problem for the reactive engine.