I have to design an egg drop experiment for a teaching project. I'll describe the project and how everything works, then the students have about half an hour to create a container to shelter the egg so that it doesn't break from a fall of about 20 feet. The sticking point is the time limit. I obviously want them to build contraptions that will work, but I don't know what materials to give them for them to build it in that short of a time without making it TOO easy (like giving them a box and cotton balls; they'd know exactly what to do with it, and wouldn't have to work for it at all). Any ideas?