Sutherland figured out how graphic interaction ought to work, with the computer recognizing near points and connecting them. What we now call "snap". He had the key idea of CAD - you can draw with more accuracy if the computer helps.

That demo is running on the MIT TX-0, a transistorized version of Whirlwind and the predecessor of the PDP-1. It was somewhat obsolete at that point, so projects like this could get time on it.

He brushes over the zoom out, which I think was pretty impressive for a computer of this time. There is a lot of redrawing/recalculating going on there. Would be impressive on a 80s microcomputer.