Don’t Wreck My PC! puts a click-proof barrier across the screen, then lets you cut holes in it with the mouse. Your kids can click through the holes, but not elsewhere. It lets you save the way you’ve cut those holes for the next time you let your kids do whatever they’re doing.
A question: when you save, what should I call the thing you save? In Excel it would be a “workbook”. In Word, a “document”. But what about here? I have my own idea, but maybe someone can come up with something better? Here’s how the UI looks for that step (screenshot slightly shrunk):