A list of twenty things cannot show you that they are a circle

The background

Twenty or so pieces run in one browser tab — instruments feed a store, a check reads it, a forecast follows — and one screen let you stop any of them. It was a table: a lamp per row, a sentence, buttons to stop and restart. All true, and none of it showed the shape. Those pieces are a circle, and stopping one greys a row, which says nothing about what that row was feeding.

The requirement

The system drawn as the connected thing it is, its connections taken from the actual wiring rather than a drawing kept current by hand, and stopping something having a visible consequence elsewhere on the screen.

The options considered

The first attempt is the useful part. It drew twenty boxes in rows, two with a bespoke display and eighteen the same card, and no connecting lines — from the inside, staging; from the outside, a picture of twenty identical boxes. It came out that way because the pieces had nothing to draw: each published a sentence about itself, and a display wanting a bar would have to pick numbers back out of prose, inventing figures the moment somebody reworded one. So the status schema gained an optional list of figures: name, number, unit, and the bound it is measured against.

The lines came from a machine-derived record of who publishes where and who listens, so the picture renders the wiring rather than describing it again and cannot drift; a check fails the build if a piece is undrawn, or a connection neither drawn nor listed as hidden.

The demo

Open it at the operator view and stop the vessel: two boxes along, the instruments start saying they have nothing to sample.