Function
An upcoming step shows the lesson's thumbnail and invites watching it. A finished step recedes — no thumbnail, a muted title, an offer to watch again — and announces its state by name, so it never rests on the marker's colour alone. The current step is featured as a card with the poster, a "you are here" eyebrow and one primary action: continue when partly watched, start when not.
Each step draws its own piece of the rail: a marker for its state and the connector below it, filled once the step is finished. Drawing the rail per step keeps it aligned however tall a wrapped title or the card grows.
Every form exposes one announced, tabbable link. Thumbnails and posters
repeat that destination for pointers only; the whole step is a pointer
target through the action's stretched ::after.
One lesson on a module's route.