shivanesh21/Expense-Spliter ? reverse-engineered prompt

Build me a full stack expense splitting app where a group can add shared expenses and the app figures out the smallest number of payments needed to settle up.

I want a clean React front end and a Node and Express backend with MongoDB for saving users, groups, expenses, and balances. The app should let people split an expense equally, by exact amounts, or by percentages, and it should validate the numbers so they always add up correctly. After each update, show the current balances and an easy to understand settlement plan that explains who should pay whom and why that path was chosen.

Please make it feel real time, so if one person adds or edits an expense, everyone in the group sees the update right away. I also want a simple modern UI that works well on desktop and mobile, plus the basic API routes and data models needed to make the app usable end to end. If you need to check anything current while building, look up the latest docs online.