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
iPolar
iPolar generates sailing yachts polars of cruising yachts and cruiser racers from a very simple set of data
$10.99
PRICE
$10.99
No in-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 3.2
5 ratings · Below Average
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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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/
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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 iPolar: map the core Sports workflow, choose the smallest differentiated feature set, define the data and monetization boundaries, then prototype the riskiest user journey first.
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App evidence
Original App Store material. Ratings and screenshots describe the existing app, not proof of demand for your version.
Screenshots
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App Store description
iPolar generates sailing yachts polars of cruising yachts and cruiser racers from a very simple set of data. iPolar is fully functional on iPad, iPhone & iPod touch. Mandatory Input data: - Length Overall - Displacement - Mainsail area - Jib area (units can be set to metric or imperial) Optional data: - Length Waterline - Symmetrical Spinnaker area - Assymetrical spinnaker aera For each sail configuration in the input data, iPolars will compute a performance polar decribing the yacht performance in kts for wind strength ranging from 4 to 30kts and true wind angles ranging from 0° to 180° Output format: Resulting polars can be visualized as a graph and as a table of numbers within iPolar. In addition, the polars can be sent directly to the weather/routing application Weather4D Pro. Limitations: iPolar has been developed to generate accurate polars of cruising yachts. It currently does not handle multihulls and is limited to yachts with a size ranging from 8 to 20m. The accuracy of the application decreases for yachts whose displacement to length and sail area to displacement ratios are outside the usual range for production cruisers and cruiser racers.
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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
Implement social features to share activities and achievements.
Assumption to check: Limited user engagement features like social sharing.
Validate with people who use this workflow before building.
Hypothesis 2
Use modern design principles for a more appealing interface.
Assumption to check: Basic UI/UX can be improved.
Validate with people who use this workflow before building.
Hypothesis 3
Add graphs and stats for activity performance tracking.
Assumption to check: Lack of detailed analytics for activities.
Validate with people who use this workflow before building.
Hypothesis 4
Focus on user feedback to enhance core functionalities and fix bugs.
Assumption to check: 3.2 rating indicates user dissatisfaction.
Validate with people who use this workflow before building.
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-maps
zustand
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.
