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
Whistle Sounds
If you need to blow the whistle but don’t have a real whistle on hand, you’ve found the right app! This app features high-quality whistle noises that sound just like a real whistle – no one will even know the difference!
$0.99 · In-app purchases
PRICE
$0.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 3.0
9 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.
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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/
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 Whistle Sounds: map the core Entertainment 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 sound library with user-generated content or partnerships.
Assumption to check: Limited sound selection compared to competitors
Validate with people who use this workflow before building.
Hypothesis 2
Implement adaptive bitrate streaming for better playback.
Assumption to check: Inconsistent audio playback quality
Validate with people who use this workflow before building.
Hypothesis 3
Add features for sharing sounds on social media.
Assumption to check: Lack of social sharing options
Validate with people who use this workflow before building.
Hypothesis 4
Enable offline playback by allowing users to download sounds.
Assumption to check: No offline access to sounds
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
If you need to blow the whistle but don’t have a real whistle on hand, you’ve found the right app! This app features high-quality whistle noises that sound just like a real whistle – no one will even know the difference! This app is perfect for sports coaches and athletic trainers – no need to keep old fashioned whistles around any longer! Play the whistle sounds loudly to be heard across the soccer field or running track. These whistle sounds can also be used indoors on the basketball court or along side the swimming pool. Signal your athletes to start and stop reps during practice, or make the tough call for a foul during games! Even if you’re not an athletic coach, these whistle sounds may come in very handy! Keep whistle sounds on hand to call for help in a scary situation if you are walking alone at night or in dangerous areas. Whistles can also be used to call someone’s attention in a noisy place. With various whistle tones and types available, you’ll be sure to find the perfect sound to fit your needs! Check out these great sounds and never be left without a whistle again!
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
expo-av
react-navigation
react-native-gesture-handler
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.
