A node in the view tree returned by an app's view/1. Plain struct, no macros — built via the constructor functions in Harlock.Elements (text/2, vbox/1, box/1, etc.).

You'll see Harlock.Element.t() in typespecs but normally won't construct one directly. Pattern-matching against the struct is fine if you're writing renderer extensions; the field shapes are stable on 0.x releases.