The doctrine of the church as a mastery ladder — what the church is (ekklesia; people of God, body of Christ, temple of the Spirit), visible and invisible, its four attributes, the marks of a true church, church government and officers, the ordinary means of grace, baptism and the Lord's Supper, church discipline, worship and the regulative principle, and the church's mission. Each mode trains a different skill; the final exam ranges over the whole course. Unlock each subtopic by scoring at least 90% on its mastery check. Cards you grade enter spaced review: the dashboard tells you when they fall due.