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
Simple Car Loan Calc
Simple Car Loan Calculator helps you make informed decisions when buying a car
$0.99 · In-app purchases
PRICE
$0.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 5.0
1 ratings · Top 5%
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 Simple Car Loan Calc: 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
Add budgeting tools and alerts for better user engagement.
Assumption to check: Limited features for financial tracking
Validate with people who use this workflow before building.
Hypothesis 2
Incorporate graphs and charts for payments over time.
Assumption to check: Lack of visual representation of loan data
Validate with people who use this workflow before building.
Hypothesis 3
Implement user accounts to save history and preferences.
Assumption to check: No user account or history saving options
Validate with people who use this workflow before building.
Hypothesis 4
Allow users to set preferences for currency and payment frequency.
Assumption to check: Limited customization options
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
Simple Car Loan Calculator helps you make informed decisions when buying a car. Whether you're considering a new or used vehicle, our easy-to-use calculator shows you exactly what your monthly payments will be. FEATURES: • Calculate monthly payments for new and used cars • Factor in trade-in value and down payment • Include sales tax in calculations • See different interest rates for new vs. used vehicles • Visual amortization schedule showing how your loan balance decreases over time • Track total interest paid over the life of the loan • All calculations saved automatically for easy reference PERFECT FOR: • Car shoppers comparing different loan scenarios • Buyers negotiating at dealerships • Anyone refinancing an auto loan • Financial planning and budgeting HOW IT WORKS: Simply enter your car's sale price, trade-in value, down payment, sales tax rate, interest rate, and loan duration. The app instantly calculates your monthly payment, total interest, and provides a detailed amortization schedule showing principal and interest breakdown over time. Your data is stored locally on your device for privacy and convenience. The app remembers your last calculations, making it easy to adjust numbers and compare different scenarios. No ads. No subscriptions. No data collection.
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 Navigation
TypeScript
Zustand
react-native-paper
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.
