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📜 WAYPOINT LESSON

Checkpoint: OOP

⭐ beginner⏳ 15 min read📍 Lesson 37 of 204

One graded challenge: a class with a real invariant, const-correct interface, and one polymorphic use.

Checkpoint — OOP. Pass the graded challenge below to finish the module.

A Counter class (encapsulation + invariant) and an area function over shapes (polymorphism) — the module's two halves in one artifact.