NEXO: Daily clinical reasoning game with ICD-10 feedback

Hey everyone, NEXO came out of something that bothered us in every medical quiz app we tried: you answer, you are told right or wrong, and that is it. But in clinical reasoning, being wrong by a little and being wrong by a lot are not the same thing. So NEXO uses the ICD-10 tree as a ruler. You get a case with up to six progressive clues and you submit a diagnosis. The feedback tells you how far your answer sits from the correct one: exact code, same category, same group, same chapter, or a different chapter entirely. Mistaking cholecystitis for appendicitis lands in the same acute abdomen neighborhood. Mistaking it for a myocardial infarction does not. Those are different kinds of wrong, and the app says so. There are 649 cases across 25 specialties in six languages. Beyond the daily case there are two other modes: Continents, organized by regional epidemiology, and Multimedia, built on real clinical images and auscultation across 18 modalities. Every case is checked against NEXO Core, an internal knowledge graph of 11,500 clinical concepts drawn from 27 reference textbooks. A clue only survives if it appears among the neighboring concepts of the proposed diagnosis. Structural audit, not a read-through. Built by three of us in Brazil: a physician in training, a clinical oncologist, and a data scientist. The daily case is free forever, with no ads. Happy to answer anything.