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
Inches to mm converter
A handy app to convert between inches and millimeters
$2.99 · In-app purchases
PRICE
$2.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.4
13 ratings · Top 30%
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 Inches to mm converter: map the core Productivity 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 support for other units (cm, feet) to expand use cases.
Assumption to check: Limited functionality, only converts inches to mm
Validate with people who use this workflow before building.
Hypothesis 2
Implement a history feature to log previous conversions.
Assumption to check: No option to save or track history
Validate with people who use this workflow before building.
Hypothesis 3
Allow users to change themes or units displayed.
Assumption to check: Lack of customization for display
Validate with people who use this workflow before building.
Hypothesis 4
Redesign UI for a modern look with better user engagement.
Assumption to check: Not visually appealing
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 handy app to convert between inches and millimeters. "Flip" button lets you easily switch between "Inches" and "Millimeters". Supports fractions. Results are shown in the decimal and fractional forms. App's Settings: - Rounding to the specified number of decimal places: for decimal numbers, you can select the number of decimal places you want to display. By default, the app displays 2 decimal places. To round results to the nearest whole number, select 0 decimal places. - For fractions, you can select rounding to the nearest 1/2, 1/4, 1/8, 1/16, 1/32, 1/64, 1/128, 1/256. By default, the app rounds fractions to the nearest 1/32. If you do not need to round fractions, just select "-". Sends results and history via email. Conversion history. Supports both portrait and landscape orientation.
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
TypeScript
React Navigation
Async Storage
Styled Components
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.
