Grounded, or refused
An answer key may only rest on a source-validated path. When the substrate cannot ground one, no question is produced — … candidate questions were refused rather than emitted.
Questions that can show their working.
Every stem, key, distractor and explanation is built from a compiled medical substrate. Each answer comes with the mechanism traced step by step, the tier of the evidence behind each step, and — where the source is a journal, guideline or drug label — the citation. Where the substrate is thin, it says so instead of guessing.
Weakness is a region, not a label
Each question records the exact nodes it tests, so a wrong answer points at specific mechanisms — and at the neighbouring ones you probably have not met yet.
It improves when the substrate grows
Questions are regenerated from the substrate rather than written once. Every addition to the underlying knowledge base improves questions that already exist.
Choose an examination
Questions are drawn in the proportions the exam publishes. Where an exam publishes no weighting, areas are weighted equally and it says so.
Learn a subject
Pick a specialty, or type any subject — a whole field or one narrow corner of it.
Where you are strong and weak
This is the substrate graph itself, with your mastery as a field over it. Colour is mastery; a dashed ring means the estimate is inferred from neighbouring questions rather than measured — a suspicion, not a result.