Case Study: Billi (in progress)
Billi is the first real project we will scaffold with prototype-kit. The four-week MVP cycle begins 2026-04-20; this page will update with actual outcomes as the cycle runs.
Case Study: Billi
Billi is a personal finance app designed for the Mexican market — specifically for university students aged 18-25 who want to track daily expenses without the complexity of traditional budgeting tools.
This case study is in progress. The Billi MVP build cycle begins 2026-04-20 and runs for four weekly cycles ending 2026-05-17. Below we state the hypothesis we are testing; we will update this page with observed outcomes after each cycle.
Hypothesis we are testing
A student with no development background can go from three short markdown docs (product-brief.md, ux-vibes.md, screens.md) to a running React prototype in the same afternoon by using the prototype-kit workflow described in this Playbook. Specifically, we expect:
- Documentation-to-first-render in under three hours.
- A prototype polished enough to demo in front of a jury without apology.
- Less than one manual intervention per generated screen.
What we expect to learn (in priority order)
Where product-brief.md specificity actually matters. We will track which brief sections shape the generated UI most: the problem statement, the target user, the MVP feature list — and compare outputs when any one of them is vague vs. specific.
Whether ux-vibes.md outperforms hex codes. We will deliberately run one iteration with only reference sites and tone adjectives, and one with hex codes and typography specs, then compare which produces a more coherent visual result.
How the agent handles ambiguity. We will note every time the agent asks a clarifying question versus fills in a plausible default — and whether the defaults were acceptable.
Status
Week 0 (planning) is complete. Cycle 1 begins 2026-04-20. This page is scheduled to update at the end of each weekly cycle.