IconButton

Square or round, two sizes. Anticipatory data-pressed flips on pointerdown for tactile feel.

— Resting

— The weight is the state

Pass weight="solid" for the control that is currently doing something — the open panel, the running playback. A background tint alone cannot say that in night mode, where every tone is the same red; a filled glyph can. Each pair below is the same control off and on.