Thin · Responsive — You Drive
ObservableThick · Adaptive — It Infers
inferring: deep reading
Two copies of the same article. On the left, you drive: the controls are observable and yours. On the right, the system infers from how you scroll: rush and it triages for skimming, dwell and it settles for deep reading. Same lever, different hands.
The core distinction between observable and latent adaptation, made physical. The left pane's model of the reader is a slider they can see and set. The right pane's model is an inference felt only in operation. Everything in adaptive typography, consent and predictability included, follows from who is driving.