Final answer:
Lilly should use the animation principle of bouncing to depict the ball's motion in her game.
Step-by-step explanation:
Lilly should use the animation principle of bouncing to depict the ball's motion in her cartoon-like game. The principle of bouncing involves showing the ball's movement as it is tossed on the ground and bounces back up. This can be represented by animating the ball's upward trajectory after each bounce, conveying its elasticity and the force exerted on it.