Since there doesn't seem to be a lose condition, this is actually an idle game (some ducks collide with the smiley on the catapult so all you need is wait for your score to climb)... Maybe only angry smileys (when the ball has been shot) should actually collide with the birds?
It would be nice if "trick shots" would be honored, like hitting multiple ducks with one shot, or hitting another duck with a smiley that was reflected by a first hit.