1. Beginning in a standing position, your group must use the paper tubes to control the marbles' descent to a slow finish on the ground.

2. Once a marble has entered the first tube, no one may touch it with anything but his or her paper tube; no one may touch anyone else's tube; and the tubes themselves may not touch at any time.

3. If any of these rules are broken, the marbles currently in the system become contaminated and must be restarted.

4. Explain to the group that upon exiting the final tube, if any of the marbles travel in excess of 2 to 3 inches across the ground it must be restarted. This creates more challenge, and demands more precise technique to solve the problem. Otherwise they could just launch the marbles down the tubes quite easily.