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
Big Mac Index App
The Big Mac Index App intends to show whether currencies are at their "correct" value
$0.99 · In-app purchases
PRICE
$0.99
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.
Build your own version
Build Kit
Make this idea yours
A product spec, screen plans, and build steps for your coding agent.
First kit free with a verified email
Add to a Remix
Combine features and design from your favorite apps.
Kit ready. Verify your email to download it.
Generating… usually about a minute.
Make it yours Optional
What should your app do differently? Your note travels with the kit so your coding agent builds around your idea.
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.
JavaScript is required to complete mailbox verification.
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 Big Mac Index App: map the core Finance workflow, choose the smallest differentiated feature set, define the data and monetization boundaries, then prototype the riskiest user journey first.
Preview ready. Verify your email to reveal and copy the full prompt.
JavaScript is required to complete mailbox verification. Return to this prompt preview.
Continue in Rork >
Affiliate link: CloneChart may earn a commission at no extra cost
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
Provide detailed historical price trends and comparisons.
Assumption to check: Users may find limited historical data frustrating.
Validate with people who use this workflow before building.
Hypothesis 2
Add social sharing options for users to compare prices with friends.
Assumption to check: Lack of user engagement features like social sharing.
Validate with people who use this workflow before building.
Hypothesis 3
Implement clear subscription tiers and trial options.
Assumption to check: In-app purchase management can be confusing.
Validate with people who use this workflow before building.
Hypothesis 4
Integrate live currency conversion for better usability.
Assumption to check: Limited currency conversion 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
The Big Mac Index App intends to show whether currencies are at their "correct" value. It was invented by The Economist in 1986. For example, the average price of a Big Mac (Burger) in USA as in July 2014 was $4.80, in China it was only $2.73 (¥16.90) at market exchange rates. So The Big Mac Index says that the Yuan was UNDERVALUED by $43.1% at that time. How To Use It 1. Input the Local Price of the Big Mac Burger. 2. Press the "CALCULATE" button. 3. You will get if the currency of the selected country is Undervalued or Overvalued and which should be the exchange rate (USD Based) for that Burger price. 4. Share the results in Facebook & Twitter. Credits Developed By Pablo Paciello - @PPacie Designed By Rafaela Sinopoli - @Rafs84 HTPressableButton By He Rin Kim - @Herinkc FlatUIKit By @Grouper HTPressableButton & FlatUIKit are Licensed under the terms of the MIT license.
Written user reviews are not shown here. Check current App Store reviews >
Screenshots
< Scroll to see more >
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
Victory Native
Axios
React Navigation
@react-native-async-storage/async-storage
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.
