It Stops
Start the line. It travels across the page without asking for anything. You press pause. It stops.
It does not wait for a better reason. It does not slip away. It stays where you left it.
No alarm sounds. Nothing asks you to confirm that you meant it. The stopped line makes no claim beyond the stillness you can see.
For a moment, this is the whole arrangement: one moving thing, one visible control, one response you can see.
You can start it again. You can leave it still.
Either way, the page has changed. That is enough to notice before you go on.