Thirty students watch one desktop; one of them drives

You teach GIMP by doing GIMP. Your desktop session runs with ?sharing=true&steal=false; the class opens the same URL with readonly=true added. Thirty browsers, one live desktop. Every menu you open, every layer you mask, they see in real time: actual pixels, not a compressed video feed of your screen.

Then you call on Maria. She reopens the link without the readonly flag, and now her cursor is on your desktop, doing the exercise while everyone watches. No screen-share handoff, no "can you give me control," no installing a meeting client on thirty machines.

The difference between watching and driving is one query parameter.