← Steane codeEntry facetDerivations & guidesSelf-contained Level-2 arguments and worked explanations.Steane code — Level-2 mapFrom the Hamming matrix to the `[[7,1,3]]` quantum codeWhy T is missing and how universality is restoredWhat the Steane hardware demonstrations establishedSyndromes, lookup decoding, and fault-tolerant extractionWhy the Steane Clifford gates are transversal