Friction
Testing Effect + Spaced RepetitionThe unit of knowledge is not the answer but the question you can't yet answer. Understanding arrives through repeated retrieval failure.
The Unit
The Question — specifically, questions that reveal gaps. Each tracks your struggle history.
Key Mechanism
Forced retrieval before hints. Spaced repetition scheduling. Confidence calibration.
What It Produces
Durable, retrievable knowledge. You know something when you can recall it on demand.