Build your own Splitwise.

# Build an original app inspired by Splitwise

You are an experienced mobile product designer and mobile engineer. Build a working, polished MVP from the brief below. Implement the core journeys end to end; a static mockup is not sufficient. Inspect the current environment, make sensible implementation decisions, and get started. Ask a question only if a missing answer genuinely blocks implementation.

Starting platform: iOS / Android. Explicit customized Product & audience and Tech stack requirements take precedence over this starting target.

## Product & audience
Build an original native expense-splitting app called Fairshare, inspired by Splitwise. It is for one person keeping a transparent ledger for a trip or household. The primary journey is creating a group of named participants, recording who paid an expense, assigning equal or exact shares, and seeing balances plus manually recorded settlements. Deliver native iOS/Android projects; make clear that this first edition is a local ledger, not synchronized member accounts or a payment service.

## Design
Use an original readable group list, expense timeline, amount entry sheet, and balance summary. Show currency and who paid before saving. Explain how each split was calculated and display recorded settlements separately from expenses. Provide accessible numeric entry, screen-reader amounts, large targets, and confirmation/undo for removing financial records.

## Features
1. Groups and participants: create a trip/household with a fixed currency, add participant names, and archive finished groups. Prevent removing a participant referenced by existing records without a clear migration or archive rule. No invitations are sent in the local edition.

2. Expenses: enter title, date, payer, amount, and included participants. Support equal splits with a deterministic remainder rule and exact shares whose sum must equal the total. Preview every share, edit an expense, and prevent duplicate commits on repeated taps.

3. Balances: derive each participant’s paid total, owed share, and net balance from the ledger. Show a deterministic suggested settlement plan whose transfers preserve those net balances. Label suggestions as calculations, never as money already transferred.

4. Settlements: manually record an outside payment between two participants, with amount, date, and optional note. Validate currency and participants, allow correction, and show the before/after balances. Record reversals explicitly rather than hiding them.

5. Offline portability: add and inspect entries without connectivity, export a human-readable CSV plus versioned JSON backup using native sharing, and import a validated backup with preview. Explain that sharing a file does not create live collaboration or payments.

## Tech stack
Use Flutter/Dart with SQLite and actual iOS/Android project directories. Keep integer minor-unit arithmetic, split allocation, and settlement planning in pure tested modules. Use native file pickers/share sheets with cancel/error states; broad storage or contact permissions are unnecessary. Retain a suitable existing native project, but do not substitute a WebView. Shared accounts or cross-device editing would need an authenticated backend and conflict handling as a later explicit extension.

## Data & behavior
Group {id, name, currency, minorUnitDigits, archivedAt}; Participant {id, groupId, name}; Expense {id, groupId, title, payerId, amountMinor, date, revision}; ExpenseShare {expenseId, participantId, amountMinor}; Settlement {id, groupId, fromId, toId, amountMinor, date, note, reversesId}; ImportManifest. Persist parent and shares atomically, validate balance conservation, and recompute balances from records. Avoid floating-point money and implicit exchange rates; support a single documented currency per group.

Acceptance checks and scope:
Split 10.00 among three people, verify deterministic cents and zero total net balance, then record a settlement and edit an expense. Test invalid exact sums, duplicate save, over-settlement warning, deletion/undo, canceled file access, offline relaunch, and backup restore. Build both native targets and verify large text plus locale-aware numeric input. Exclude actual payments, bank connections, receipt OCR, currency conversion, synchronized users, debt enforcement, and financial advice.

## Originality and assets
The named product is a reference for general workflows only. Use an original product name, visual identity, wording, layout, and assets. Do not copy proprietary code, branded logos, distinctive screens, private APIs, paid templates, or protected media. Use original or appropriately licensed sample data and assets. Build from this brief rather than scraping the reference service. Do not imply affiliation with the referenced company.

## Implementation quality
- Make every visible control work, with clear loading, success, empty, validation, and failure states. Remove controls for unimplemented features.
- Support the target platform and responsive or resizable layouts where appropriate. Use platform-appropriate accessibility semantics, labels, keyboard operation, visible focus, sufficient contrast, and reduced-motion preferences. Provide alternatives for drag-only interactions.
- Validate inputs at the relevant boundary. Treat imported or user-generated content as untrusted; render it safely. Confirm destructive actions or offer undo.
- Keep state changes reliable across navigation and reloads. Never silently lose edits. Handle persistence and network errors with an actionable message.
- Keep the scope realistic. Prioritize the complete primary journey. If a custom Features section differs from the baseline, update the data model, design, and acceptance checks to match it; explicit custom requirements take precedence over baseline assumptions.
- Provide realistic original sample content and a useful empty state. Keep sample data clearly separate from user-created data.

## Delivery and verification
1. Inspect the repository and outline the implementation in a few sentences.
2. Implement the app and connect its actual data flow. Continue until the primary journey works.
3. Run appropriate checks and test the acceptance cases above on the target platform. Verify responsive layouts and keyboard navigation when browser tools are available. For native projects, build with the available SDK and test an emulator or device when possible; report any missing native verification honestly. For games, verify the rules and gameplay loop, not only the menus.
4. Fix observed failures, then provide the runnable result, setup/run instructions, a brief explanation of what is implemented, and any specific configuration or verification limits.

This is a focused MVP. Do not add billing, AI services, or unrelated features unless explicitly requested in the brief. Start building now.