In CoCalc, one of the foundational ideas is that it should be very easy to see code and Jupyter notebooks from 5 minutes ago. Hence every editor in CoCalc incl

In CoCalc, one of the foundational ideas is that it should be very easy to see code and Jupyter notebooks from 5 minutes ago. Hence every editor in CoCalc includes a TimeTravel button, which you click on to get a side-by-side view of your file (or notebook) and a slider that lets you go back and forth in time at high resolution. I designed CoCalc this way because when I taught data science classes, I would walk around a classroom while the students were doing an in-class exercise and they would often say to me "I had this part figured out 5 minutes ago, but I messed it up." Some people (including me!) who get used to working this way get very addicted to it, and can hardly imagine working any other way. This is vastly superior to depending on undo/redo, and I use it all the time when doing deep coding projects. It's also useful for collaboration, since it makes it easier to figure out what somebody else did with a file or notebook.