XXXWhen we were young it was the "do-over". It was XXXsimply a part of the sociology of youth. Today, the XXXgreatest tool, more valuable possibly than the PC that makes it possible, is the UNDO.
Edit, Undo; that little backwards arrow; Ctrl Z. How simple to go backwards in time. Of course, films like The Butterfly Effect and short stories like Ray Bradbury's "A Sound of Thunder" show the danger of the UNDO. The Butterfly Effect or "sensitive dependence on initial conditions" is the very real, but very SURreal science of chaos. Check out these Butterfly Effect sites, here or there, and, should you choose (hint, prompt), think of a situation in which you would like to have or see a do over or UNDO, but also include what may very well be the butterfly effect.
For the heck of it (not an assignement but suggested reading), click here to read Ray Bradbury's "A Sound of Thunder."