Use Devin to build and then slim down a calculator app
A Scott Logic developer used Devin to create a calculator app, then had it map out a refactor that shrank the codebase by about 60%.
- What they did
- James Camilleri started with a carbon-emissions spreadsheet and a repo linked to Devin. His first pass with Electron did not work, so he reset the approach and asked for a TypeScript/React version instead, beginning with the calculation logic and then the interface. Devin then helped by outlining work, making branches, building changes, and opening pull requests for review.
- How it went
- After several calculators were added, the code started to repeat itself, so Camilleri asked Devin to inspect the app and draft a refactoring plan. He sent that plan back in pieces, and the cleanup reduced the project size by roughly 60%. The whole app was finished in just over a week, but he could not inspect every line, so he leaned on tests and spot-checked important logic.
- Tips
- This kind of workflow works best if you keep the task in small stages and review the key logic yourself. Camilleri also found it helpful to start fresh sessions regularly to reduce context drift; the build used about 155 ACUs and cost roughly $350, so budget for retries.
Try it yourself with Devin
Build a [small web app] in [framework] that handles [calculator types or similar tasks] from [source data or a spreadsheet]. Start by implementing the core calculation models, then add the UI, tests, and any wiring needed to make it usable. After the first version works, inspect the codebase for repeated logic, unnecessary code, and awkward structure, then write a refactor plan in small steps. Present the plan and stop for my approval before making changes. For any step that could delete, replace, or submit code, pause and ask me to confirm before continuing. After each approved chunk, run the tests, report what changed, and keep going until the app is clean and stable.
Fill in the [brackets]. Agents can make mistakes, so review anything before it is sent, paid or deleted.
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