LeftOver

A practical tool for a household

LeftOver is a personal project built for one household sharing a budget. The work centres on a recurring question: once upcoming bills are covered, what is actually left? A balance alone cannot answer that when income and bills arrive on different dates.

The current app brings that timing into view through a household overview, a budget organised by month or pay cycle, a calendar and a dedicated bills reserve. Tax records, savings, debts and an AI Coach sit alongside those everyday tasks.

The screens in this case study show the current interface with fictional sample data. They were captured from the same version running on leftover.au, version 0.4.4, in October 2026.

Make the next action clear

Home puts the reserve balance, unpaid bills and upcoming dates together. On desktop, a bill list and calendar sit side by side so the household can move from an overview to a specific payment. On a phone, the same information becomes a sequence of cards above five primary navigation tabs.

The wider finance tools are grouped under Home. This keeps the main navigation focused on the tasks that recur most often: checking the budget, looking at dates and managing bills.

Separate funding from payment

A bill can be due, have money set aside for it, or already be paid. Those are different states, and the budget makes each one visible. It shows the total due, the amount paid, what remains and how much still needs to be set aside.

The same records can be viewed by calendar month or pay cycle. Individual payments can be marked paid and their actual amounts recorded, while the bills list holds recurring schedules and one-off costs. The calendar provides another way to see when bills and income fall.

Give the bills reserve its own place

The reserve records money put aside for bills and the movements in and out of that balance. The interface explicitly distinguishes a recorded balance from expected income: a forecast does not increase the money available today. Recording a movement documents an action taken at the bank; the app does not transfer money.

An outlook extends the view over three, six or twelve months. It shows the effect of planned bills and expected income, including the low point before income arrives. The assumptions remain visible so a projected closing balance is not mistaken for cash already available.

Keep the wider picture close

Tax brings receipts, working-from-home hours and payment summaries together by Australian financial year. It includes an estimate based on the recorded information and an accountant pack for review.

Stash records savings, assets and debts, with a net-worth view and AI assistance for entering information. A linked reserve entry can use the recorded reserve balance.

Coach can use the budget context to explore questions such as “can I afford this?” When it proposes changing a record, the interface asks the user to approve or reject the change before applying it. This gives the household a way to inspect an AI suggestion at the point where it would affect their records.

One budget across devices

LeftOver runs in a browser, can be added to a phone’s home screen, and also ships as a Mac app. It supports device-local use; signing in with Google enables Firebase household sync. The Mac version stores the budget in a local file and receives updates in the app.

Because this is a tool used for everyday records, recovery is part of the design. Backups, safety copies and explicit choices when combining local and synced data help people understand what will be kept before a budget is replaced.

Design and implementation together

I work across the interaction design and implementation. The current codebase uses React 18, JavaScript, Vite and Tailwind, with Electron for Mac, Firebase for household sync and an Anthropic relay for AI features.

Money, dates, bill schedules, reserves and tax calculations live in domain modules separate from the interface. Automated checks cover those rules as well as sync, storage and release behaviour. The release workflow tests and builds the web and Mac versions before publishing.

The result is a working household tool that continues to evolve through use. Its value in this portfolio is the connection between clear interaction design, explicit financial states and the engineering needed to keep records dependable.