The foundations of the case system (four NT cases, stem-vowel principle, article as anchor), genitive and dative cases, the three 1st-decl subpatterns with Step 1/2/3 derivation of the pure-α paradigm, the full 24-form article with its bare 24-cell underlay, case-governing verbs, and the Chapter 5 vocabulary. Unlock each subtopic by scoring at least 90% on its mastery check.