Projectile Popper

Build this Projectile Popper using an empty 32 oz Gatorade bottle, a string, rubber bands, drill (other options), scissors, goggles, bead, ping pong balls, and a box cutter (or knife). (NOTE: Adults should prep the Gatorade bottle by cutting it with the box cutter and drilling the hole in the lid for young children.) Once you have built the Projectile Popper, then engineer it! Can you improve this design? Can you create a game using Projectile Poppers? What is the best rubber band to use? What other bottles can you use?