Three layers: what we know, what we can show, and how we decide what's next.
Atomic skills, prerequisites, tiers. One graph per topic. Each skill has lessons (1–3 variants), questions, prediction prompts.
Per-student, per-topic. Accumulates signals from every interaction. Drives what happens next.
Confidence, accuracy, time, guessing
Which card, skill, variant, format
Render the right card
Write back to Student Model