Nouns and cases, one layer at a time.

The noun compass: dictionary form, subject, gender, and declension pattern

Number, regular plural endings, spelling restrictions, stress, and plural stems

Location, topic, stable singular endings, and the restricted second locative

Direct objects, goal-directed в/на, and the first systematic role for animacy

Absence, reference, source, possession, small quantities, and restricted partitive forms

The major plural formation challenge: zero endings, -ов/-ев, -ей, stem repair, and quantity

A fully derivable animacy system: nominative plural for inanimates, genitive plural for animates

Regular -ах/-ях endings, plural stems, locations, topics, and full phrase building

Recipient, target, experiencer, age, necessity, and movement toward

Regular -ам/-ям, plural recipients and experiencers, к/по, and oblique numeral phrases

Means, accompaniment, roles, states, spatial relations, and spelling after sibilants

Regular -ами/-ями, special -ьми forms, plural means, companions, roles, and case-system capstone

Irregular stems, indeclinables, adjectival nouns, personal names, surnames, places, and extra case remnants