Growing up, I’d venture that most people encountered an Etch-A-Sketch at some point. It was a fun little toy, if a bit strange. It let you etch a picture using the two dials, which controlled vertical and horizontal movements. If you wanted to make anything other than just a boring skyline, you had to master the art of twisting both knobs at the exact same time, at a very steady pace. The great thing was that if you messed up, you only needed to shake the toy, and you were left with a clean slate. If you want a return to those simpler times, you can download an app for your Mac that lets you shake away mistakes.
Shake to Undo is a simple app for your Mac that is undoubtedly inspired by the Etch-A-Sketch. It uses the sudden motion sensor in the laptop and triggers the Command+Z function. This is, of course, the default command for Undo. Of course, it’s really not a wise decision to shake your laptop, unless you have an SSD. Then by all means, shake it all you like. Just keep a firm grip, as there is no undo for accidentally tossing your laptop on the other side of the room.