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
Kids Paint: Planes & Trains
Private offline coloring.
$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
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A product spec, screen plans, and build steps for your coding agent.
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Combine features and design from your favorite apps.
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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.
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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 Kids Paint: Planes & Trains: map the core Graphics & Design 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
Expand the range of brushes, colors, and stamps.
Assumption to check: Limited drawing tools and options for customization.
Validate with people who use this workflow before building.
Hypothesis 2
Implement a more user-friendly saving and sharing process.
Assumption to check: Difficulty in saving and sharing artworks.
Validate with people who use this workflow before building.
Hypothesis 3
Add advanced features like layers and effects for older children.
Assumption to check: Not engaging enough for older kids.
Validate with people who use this workflow before building.
Hypothesis 4
Provide clear explanations and value for each in-app purchase.
Assumption to check: In-app purchases may confuse parents.
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
Private offline coloring. One purchase. No subscription. No ads. No in-app purchases. No account. Kids Paint: Planes & Trains is a coloring app for kids with 613 train, plane, and boat coloring pages: 244 trains, 197 planes, and 172 boats. Explore steam engines, subways, bullet trains, jets, biplanes, helicopters, tugboats, sailboats, ferries, fishing boats, and many more. Each vehicle is named on its page. Kids color with a brush, draw freely, erase mistakes, undo changes, clear a page, save their work, and print finished pictures. Free Drawing offers a blank canvas for original pictures. Coloring works offline after installation. Artwork stays on your phone or tablet. Child Lock works with your device’s built-in single-app controls to help keep kids in the app. Buy it once, own it forever. Built by a mom and dad, for their kids. Just coloring.
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
@react-native-async-storage/async-storage
expo-gl
react-native-share
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.
