CoperachApp

The problem

When people split costs — roommates, couples, family, a trip — the ledger lives in phone notes and in the memory of whoever paid. Nobody is sure who owes what, and the awkward conversation shows up at the end of the month. I started from one design premise: the arithmetic was never the hard part. Typing in every purchase costs more effort than most people will spend, and an app that demands it stops getting opened. And shared spending doesn't end at a dinner halved — some payments come back every month, and some purchases are paid off in installments someone has to keep track of.

What I built

I built the app in React Native and TypeScript on a Node/Express backend with Mongoose and MongoDB. The core is the split engine: an expense can be divided evenly, by percentage or by exact amounts, and from the net balances the app doesn't list debt against debt — it returns the fewest payments that settle everyone. To cut the cost of entry I wired OpenAI into two paths: a photo of the receipt, which yields amount, merchant and category, and spoken dictation. Around that I shipped personal and group budgets, shared savings goals, scheduled and installment payments with their own calendar and reminders, household chores, onboarding, and an in-app forum. One codebase ships to both stores.