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
Inflation Calculator
Ever see a price from the past and wonder how much that would cost today? With Inflation Calculator, the answer is just a tap away.
$3.99 · In-app purchases
PRICE
$3.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.9
3,530 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 included16 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 Inflation Calculator: map the core Utilities 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
Allow users to choose different currencies or formats for results
Assumption to check: Limited customization options for results display
Validate with people who use this workflow before building.
Hypothesis 2
Implement export options for historical calculations
Assumption to check: No historical data export feature
Validate with people who use this workflow before building.
Hypothesis 3
Offer more value in the free tier or trial period
Assumption to check: Paywall may deter users
Validate with people who use this workflow before building.
Hypothesis 4
Introduce unique features like inflation prediction or graphing historical data
Assumption to check: Lack of advanced features compared to competitors
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
Ever see a price from the past and wonder how much that would cost today? With Inflation Calculator, the answer is just a tap away. Features include: - Calculate the value of the dollar over time from 1800 to 2025. - Support for 22 international currencies: - US Dollar - Euro - British Pound - Canadian Dollar - Australian Dollar - New Zealand Dollar - Japanese Yen - Swiss Franc - Chinese Yuan - Swedish Krona - Mexican Peso - Norwegian Krone - South Korean Won - Turkish Lira - Brazilian Real - South African Rand - Indian Rupee - Russian Ruble - Israeli Sheqel - Indonesian Rupiah - Saudi Arabian Riyal - Colombian Peso - Yearly updates with the latest inflation data. - Make quick calculations on the go with a companion app for the Apple Watch. - Simple and intuitive. No ads or distracting popups.
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
styled-components
AsyncStorage
i18next
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.
