The challenge
A course player competes with everything else on the device.
If a learner loses their place, cannot tell how much is left, or has to hunt for the next step, the session ends there.
Opportunity
Orientation is retention
Knowing where you are and how far is left does more for completion than any engagement mechanic.
The solution
Progress always visible, next action always in the same place.
And long-form content given the typographic treatment sustained reading actually requires.
Design decision
Continuous progress
Never something you go and check.
Position within the lesson and within the course are both always present, so resuming requires no reconstruction.
Design decision
Reading typography
Measure, rhythm and contrast tuned for attention.
Set for sustained reading rather than first impression, which is a different problem with different answers.
Outcome
Resuming became effortless.
Orientation, not novelty, is what keeps a learner in a course.