Swift lesson
Values and optionals
Use let, var, types, and nil safely.
Interactive lesson placeholder
This foundation reserves the full lesson pattern: objective, why it matters, explanation, visual/example, guided practice, independent practice, common mistake, debugging exercise, knowledge check, mini-project, and recommendation.
// Try it changeThisValue = true; // Run, observe, then explain what changed.
Checkpoint: Explain the concept, fix one broken example, and complete a short applied task.