Levels 2, 3 and 5 are meant to simulate what you would learn from GCSE and A level textbooks. The contents are meant for you to read to get an idea of what you need to know, or to skim if you think you already know it just to fill in gaps and pitfalls, but you should study it more formally alongside this if you go through the documents and don't feel you have done it in school or basically know it. These are basically quick revision notes and not meant to be a full textbook to learn from. Proofs for some things in here are deferred to levels 4 (for pure) and 6 (for stats). In many textbooks some of the proofs given in this level are provided but are oversimplified and not always fully correct (I point out common pitfalls as I go).
Latest expected release date for Level 3: April 2026.