Feature spec
Goal: Send a clear invoice after finishing a job.
- Add a client, line items, a due date, and payment instructions.
- Preview the total before exporting a PDF.
- Keep an editable draft if export fails.
App Overview
Calc for Loan
This is 15 digits Loan-Caluculator
$3.99 · In-app purchases
PRICE
$3.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
N/A
No ratings yet
Evidence scope: No current overall US chart position is available. Category-chart positions shown in discovery are a separate scope. Revenue is a directional model estimate, not verified earnings.
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Build Kit
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A product spec, screen plans, and build steps for your coding agent.
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What's included15 files
A product spec, phased build plan, differentiation notes, and screen references.
- START_HERE
- AGENTS
- EVIDENCE
- SPEC
- BUILD_PLAN
- DIFFERENTIATION
- skills/
- screens/
Preview a sample Build Kit No email needed
Illustrative example: an invoice app for independent contractors. Your kit is tailored to the app you choose; this is not its generated content.
Screen plan
Invoice editor: Client at the top, editable line items in the middle, total and preview action at the bottom.
States: Empty draft, validation errors beside each field, exporting, and a retry action that preserves the draft.
Differentiate and validate
Hypothesis: Contractors need faster repeat invoices more than more templates.
First experiment: Test duplicating a previous job with five contractors. Watch where they hesitate before expanding the feature set.
The full kit adds a phased build plan, evidence notes, tool prompts, and implementation guidance. It is a plan for your coding agent, not a finished app.
Usage: Mechanics are fair game; never reuse the original name, branding, assets, or verbatim copy.
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Free quick prompt For a smaller starting point
Quick prompt
Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.
// RORK SYSTEM PROMPT
Rork plan preview for Calc for Loan: map the core Finance workflow, choose the smallest differentiated feature set, define the data and monetization boundaries, then prototype the riskiest user journey first.
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Opportunities
AI-GENERATED OPPORTUNITY HYPOTHESES
These are generated suggestions, not verified review quotations. Check current App Store reviews and speak with users before treating a possible gap as a requirement.
Hypothesis 1
Include tooltips and help sections explaining how calculations are made.
Assumption to check: Users find loan calculators often lack detailed explanations of results.
Validate with people who use this workflow before building.
Hypothesis 2
Allow users to save and customize multiple loan scenarios.
Assumption to check: Many apps have limited customization options for loan details.
Validate with people who use this workflow before building.
Hypothesis 3
Implement graphs or charts to visualize amortization schedules.
Assumption to check: Users want better visualization of payment schedules.
Validate with people who use this workflow before building.
Hypothesis 4
Provide clear descriptions and benefits for any in-app purchase options.
Assumption to check: In-app purchases are often unclear and confusing.
Validate with people who use this workflow before building.
App evidence
Original App Store material. Ratings and screenshots describe the existing app, not proof of demand for your version.
App Store description
This is 15 digits Loan-Caluculator. Easy for loan-caluculation! (Equal Payment method, Equal Principle method, conbined extra-payment, calc remaining debt available.) [ Loan Caluculate ] ■ The following calculations are available in each of the Equal Payment method and Equal Principle method (combined extra-payment available). ・Payment per month. ・Extra payment. ・Total payment. ・Total interest. ・Remaining Debt. ・Income/Payment rate. ・Borrowing limit for the payment limit. * Extra payments are expected to pay once every six months. [ General Caluculate ] ■ 15digits display caluculate. ■ Arithmetic ( + , - , * , / ) ■ Percent ( % ) ■ Grand Total ( GT ) ■ Memory ( M+, M-, MRC ) ■ Tax caluculation ( Tax+ , Tax- ) [ NOTES ] ■ This app will result in a loan, I would appreciate your approximate estimates for the calculation. ■ Reimbursements for us to borrow your practice, please check the redemption tables issued by the source tables and loan repayment plan.
Written user reviews are not shown here. Check current App Store reviews >
Screenshots
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Build scope
Plan a focused first version with your coding agent. These are planning assumptions, not a delivery guarantee.
Define the first version
Choose one audience and one core workflow. Use the kit to agree on its screens, data, and acceptance criteria before building.
Set boundaries
Decide which secondary features, integrations, and platform support can wait. Your version does not need to reproduce everything in the original.
Check the hard parts
Validate external services, specialist technology, data access, and ongoing costs for your chosen scope.
SUGGESTED BUILD STACK
React Native
Expo
react-native-paper
react-native-async-storage
react-native-pdf
BUILD KIT DIFFICULTY
Starter
From the Build Kit assessment.
A reliable timeline needs an agreed scope and a technical check. Ask your agent to estimate the phases in BUILD_PLAN.md after that review.
