Three hands on the desktop, two hundred eyes on the stream

A live coding workshop, two hundred and three participants. Three of them: this week's presenters: open the instructor's display with ?sharing=true and take turns driving. The other two hundred open a pipe URL with ?video, fed by an ffmpeg capture of that same desktop.

Two tiers, two URLs. Hands on the desktop is a session-sharing parameter; eyes on the stream is a pipe path with ?n=200. The audience can't wiggle the presenter's cursor because they were never in the session: they're watching a broadcast of it, one encode, fanned out.

Workshop platforms make you choose between a webinar, where nobody drives, and a shared session, where anybody might. Here the roles are query parameters.