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
Pregnancy Wheel HD
Just like the real due date calculator OB wheel used by doctors!
$1.99 · In-app purchases
PRICE
$1.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.0
7 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 included12 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 Pregnancy Wheel HD: map the core Medical 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 additional tracking features like weight tracking, symptom logging.
Assumption to check: Limited features compared to similar apps
Validate with people who use this workflow before building.
Hypothesis 2
Implement a more modern and user-friendly design.
Assumption to check: User interface can be confusing
Validate with people who use this workflow before building.
Hypothesis 3
Provide better onboarding and explanations for premium features.
Assumption to check: In-app purchase flow is unclear
Validate with people who use this workflow before building.
Hypothesis 4
Integrate forums or support groups for users.
Assumption to check: Lack of community or support features
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
Just like the real due date calculator OB wheel used by doctors! You have seen your doctor use this kind of wheel to quickly predict your due date - now get yours inside your iPad. ************* HOW TO USE ************* - Just slide the date wheel around with your finger. It's that easy! - To zoom the zodiac wheel, just click in the middle of the wheel, click again to close. ************ FEATURES ************ - Turn the wheel to set the date of last period or the date of conception, and you'll see at a glance the predicted due date. - See the dates corresponding to a number of gestation weeks - Bonus feature: predict the zodiac sign of your baby! - The wheel will remember its last position between uses. ************ WARNING ************ Date Wheels are for estimating purposes. They are not precise measuring devices and should not be relied on for exact calculations. All Date Wheels may have variations of 1-3 days in either direction.
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
Supabase
react-navigation
@react-native-async-storage
expo-date-picker
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.
