Design a Mobile App From Scratch: A Bite-Sized Daily Language-Learning App

Interview prompt, live, 30-40 minutes: "Design a mobile app that teaches someone a new language through short daily lessons, similar in spirit to a habit-building app. Walk me through your approach from scratch."

1. Ask your clarifying questions and state your assumptions.
2. Frame the core job-to-be-done.
3. Define MVP scope — one primary flow, and what's explicitly out.
4. Sketch the information architecture and justify it.
5. Wireframe the core flow, naming at least one interaction-design principle behind a specific decision.
6. Write the microcopy for a completed-lesson state and a broken-streak state.
7. Name one accessibility consideration specific to this app.
8. Propose HEART metrics for at least three categories, and explain why Retention deserves particular weight for this product.
9. Close with a one-sentence summary and the single highest-priority open risk.