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
Instant USD/JPY Calc!
Simple USD/JPY calculator app for instant currency conversion during overseas travel and international transactions.
$2.99 · In-app purchases
PRICE
$2.99
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/
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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 Instant USD/JPY 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
Implement a conversion history feature with easy access.
Assumption to check: Lack of user engagement features like history tracking
Validate with people who use this workflow before building.
Hypothesis 2
Allow users to choose other currency pairs.
Assumption to check: Limited currency options
Validate with people who use this workflow before building.
Hypothesis 3
Introduce settings for preferred currencies and themes.
Assumption to check: No user customization or settings
Validate with people who use this workflow before building.
Hypothesis 4
Offer a free trial or freemium model for user acquisition.
Assumption to check: Single payment model with no trial
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 USD/JPY calculator app for instant currency conversion during overseas travel and international transactions. Automatically fetches the latest exchange rates for instant JPY to USD and USD to JPY conversions! Perfect for travel budgeting, overseas shopping, and business transaction verification requiring fast, accurate currency conversion. Features: - Simple, intuitive interface - Real-time exchange rates auto-fetched - Bidirectional conversion: JPY to USD and USD to JPY - Always displays latest rate and update time - Number-only keypad for easy input - Large, immediate result display How to Use: 1. JPY to USD conversion - Enter amount in Japanese Yen - Tap Convert to Dollar - USD amount appears in result field 2. USD to JPY conversion - Enter amount in US Dollar - Tap Convert to Yen - JPY amount appears in result field 3. Rate refresh - Tap refresh button top right for latest rates - Rates auto-fetch on app launch too Perfect for travel budgeting, import/export transaction checks, and foreign currency pricing! Uses real-time rates for always-current conversions. Simple design - easy for anyone to use. From trip planning to on-site shopping - useful everywhere. Enjoy smooth overseas travel and international deals with this app! Paid app - completely ad-free.
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
axios
@react-navigation/native
react-native-paper
BUILD KIT DIFFICULTY
Intermediate
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.
