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
ETF Calculator Pro Savingsplan
Calculate and plan your ETF investments with the simple and intuitive calculators of ETF Calculator Pro.
$0.99 · In-app purchases
PRICE
$0.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 1.0
1 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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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 included16 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 ETF Calculator Pro Savingsplan: map the core Finance 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 advanced analytics and personalized recommendations.
Assumption to check: Limited functionality and features compared to competitors.
Validate with people who use this workflow before building.
Hypothesis 2
Focus on user experience and onboarding.
Assumption to check: Poor user reviews indicating a lack of intuitiveness.
Validate with people who use this workflow before building.
Hypothesis 3
Provide clear explanations of purchase benefits and a trial period.
Assumption to check: In-app purchases can be confusing.
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
Calculate and plan your ETF investments with the simple and intuitive calculators of ETF Calculator Pro. ETF Calculator Pro is the Pro App of "Savings Plan Calculator ETF" with more features and calculators. ETF Calculator: - Savings Plan Calculator - Withdrawal Plan Calculator - Rebalancing Calculator - ETF Comparison Pro Features: - Calculate the annual return of ETF / funds - Select sample ETFs or save your own ETFs. - Calculate your annuity or ETF withdrawals - Calculate your annual ETF / fund rebalancing - Use sample ETFs calculated from historical data - Simple and intuitive user interface Try the free savings plan ETF calculator to get an idea of the savings plan calculator. Need more features in the calculators or have ideas for new ones? Then feel free to contact us via the app settings. Thanks to @darshan394, @ryoji__iwata and @fahrulazmi, for providing the images on Unsplash.
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-native-chart-kit
@react-native-async-storage/async-storage
expo-router
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.
