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
Mini Metro
Mini Metro, the sublime subway simulator, now on iPhone and iPad.
$3.99 · In-app purchases
PRICE
$3.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.9
31,642 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 included17 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 Mini Metro: map the core Games 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
Introduce more maps and regular updates to keep content fresh.
Assumption to check: Limited levels and maps can make gameplay repetitive.
Validate with people who use this workflow before building.
Hypothesis 2
Include a tutorial or practice mode for new players.
Assumption to check: Some users find the learning curve steep.
Validate with people who use this workflow before building.
Hypothesis 3
Implement a gradual difficulty increase or hints for new players.
Assumption to check: The game can become frustrating due to sudden game overs.
Validate with people who use this workflow before building.
Hypothesis 4
Offer more free content and limit premium features to cosmetic items.
Assumption to check: In-app purchases can be seen as unfair.
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
Mini Metro, the sublime subway simulator, now on iPhone and iPad. • Included in the App Store Best of 2016 • Mac Game of the Year in over 30 countries • BAFTA-nominated • IGF award-winning • IGN Mobile Game of the Year nominee • Included in Gamespot's Best Mobile Games of 2016 Mini Metro is a game about designing a subway map for a growing city. Draw lines between stations and start your trains running. As new stations open, redraw your lines to keep them efficient. Decide where to use your limited resources. How long can you keep the city moving? • Random city growth means each game is unique. • Over two dozen of real-world cities to test your planning skills. • A variety of upgrades so you can tailor your network. • Normal mode for quick scored games, Endless to relax, or Extreme for the ultimate challenge. • Build your metro exactly how you want to with the Creative mode. • Compete against the world every day in the Daily Challenge. • Colorblind and night modes. • Responsive soundtrack created by your metro system, engineered by Disasterpeace. "If you love the city-planning aspect of Sim City but can't handle the pressure of playing god, then you may have just found your new favorite time-waster." - Ashley Feinberg, Gizmodo "Take my word for it that a game about mass-transit system design can be a tense, white-knuckle thriller." - Owen Faraday, Pocket Tactics "Mini Metro: fun game simulates planning and running public transit system." - Cory Doctorow, Boing Boing
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
Zustand
React Navigation
Firebase
TypeScript
BUILD KIT DIFFICULTY
Advanced
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.
