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 GBP/JPY Calc!
A simple and easy-to-use GBP/JPY calculator app that instantly converts currencies for 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 GBP/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 real-time exchange rate updates from a reliable API.
Assumption to check: Inaccurate exchange rates can lead to user distrust.
Validate with people who use this workflow before building.
Hypothesis 2
Add features for tracking exchange rate trends over time.
Assumption to check: Limited functionality with no historical data or analysis.
Validate with people who use this workflow before building.
Hypothesis 3
Incorporate user settings for favorite currencies and alerts.
Assumption to check: Poor user engagement due to lack of personalization.
Validate with people who use this workflow before building.
Hypothesis 4
Expand to include multiple currency conversions beyond GBP/JPY.
Assumption to check: No support for additional currencies.
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
A simple and easy-to-use GBP/JPY calculator app that instantly converts currencies for overseas travel and international transactions. It automatically fetches the latest exchange rates and instantly converts "Japanese Yen to British Pound" and "British Pound to Japanese Yen"! Perfect for UK trip budgeting, shopping in Britain, confirming pound-denominated transactions, and any situation requiring quick and accurate currency conversion. ＜Features＞ - Simple and intuitive interface - Automatically fetches real-time exchange rates - Bidirectional conversion: Yen to Pound and Pound to Yen - Always displays the latest exchange rate and update time - Easy-to-use numeric keypad - Large display for instant result confirmation ＜How to Use＞ 1. Yen to Pound conversion * Enter amount in "Japanese Yen" * Tap "Convert to Pound" button * Converted amount appears in the result field 2. Pound to Yen conversion * Enter amount in "British Pound" * Tap "Convert to Yen" button * Converted amount appears in the result field 3. Exchange rate refresh * Tap the refresh button in the top right corner to get the latest rates * Rates are automatically fetched on app launch, so use the refresh button as needed Use it for UK trip budgeting, confirming transaction amounts with Britain, checking pound-priced goods, and more! Real-time exchange rates ensure you always get the latest conversion results. Simple operation with an easy-to-use design for everyone. From trip planning to on-site shopping, it's useful in all situations. ＜Reference: GBP Usage Areas＞ As of November 2024, the British Pound is used in the following areas: United Kingdom (England, Scotland, Wales, Northern Ireland), Gibraltar, Falkland Islands, Saint Helena, etc. Please use this app for travel and transactions in these areas. Enjoy smooth UK travel and international transactions with this app! Paid app - no advertisements displayed at all.
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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
Zustand
axios
styled-components
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.
