That u Used to Work Only Once

Three lines deleted with 3dd come back with a single u, and Ctrl-r brings them forward again. Does that round trip feel obvious?

In the original vi, u went back one step only. Press it again and what you had just restored disappeared again. An undo of the undo. In its descendant Vim, you can go back as far as you like. And in Vim, undo is not a single line. Go back with u, edit something else, and most editors throw away the branch you left behind. Vim keeps it. g- walks into the road you did not take, and :earlier 10m puts the file back to where it stood ten minutes ago.

Ctrl+Z in most editors only retraces the way you came. Vim also remembers the way you did not.