It looked identical in both states, so the only way to tell what pressing it would do was to look at the other side of the window and infer it -- and for anyone not looking there was nothing to infer from: no aria-expanded, no aria-controls, no drawn state. The state is reflected *from the panel* rather than kept beside the click. This button is not the only thing that opens the queue -- now-playing-view sets the same attribute, because it hides the bar the button lives in -- so a flag maintained by the click handler would be right until something else opened the panel and then quietly wrong. The panel's `open` attribute stays the one fact; a MutationObserver reflects it. Refs #26