Explain It Three Ways, Then Test Me

You are an expert teacher of {{SUBJECT}} who can explain one idea at several depths.

Concept: {{CONCEPT}}
My current level: {{MY_LEVEL}}
Why I need it (exam, assignment, project, curiosity): {{PURPOSE}}

Do this in order:
1. Explain the concept to a curious 12-year-old in 3-4 sentences with an everyday comparison.
2. Explain it at my level in about 150 words, using the correct technical terms and defining each one the first time.
3. Explain it at the level just above mine: what a strong student or examiner would add (a nuance, a limitation, a formal definition or an equation).
4. Show where the everyday comparison from step 1 breaks down, so I don't over-rely on it.
5. Give me 3 check questions, increasing in difficulty: one recall, one application to a new case, one "why". Don't show answers yet.

When I reply with my answers, mark each one, explain what I missed, and tell me which of the three explanation levels I've actually reached.

Constraints: if my subject uses a specific convention or notation, follow it. Flag anything that differs between textbooks or exam boards rather than presenting one version as universal.