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
Harpie – Harp Tuner
The harp tuner built for harpists - not guitarists.
$2.99
PRICE
$2.99
No in-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.0
1 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 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 Harpie – Harp Tuner: map the core Music 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 presets for various harp types and tunings.
Assumption to check: Limited tuning options for different harp types.
Validate with people who use this workflow before building.
Hypothesis 2
Integrate tutorials or visual guides for users.
Assumption to check: Lack of visual instructions for beginners.
Validate with people who use this workflow before building.
Hypothesis 3
Enable offline access to sound samples and tuning guides.
Assumption to check: No offline capabilities or sound samples.
Validate with people who use this workflow before building.
Hypothesis 4
Introduce additional features like practice modes or scale exercises.
Assumption to check: Single feature focus, may not attract casual users.
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
The harp tuner built for harpists - not guitarists. Harpie tunes lever harps and pedal harps with concert-grade precision. Pluck a string and Harpie instantly shows you how many cents sharp or flat you are, with a clean gauge and a simple flat / in-tune / sharp light. WHY HARPISTS CHOOSE HARPIE * Real harp string layouts - pick your lever harp size (19–40 strings) or a full 47-string pedal harp. No more counting frets that don't exist. * Tuned for flats - lever harps in E flat major, pedal harps all-flat. Harpie speaks your language out of the box. * Auto mode - listens through your mic and follows you string to string. Hands-free. * Reference mode - tap any string to hear a warm, realistic harp tone and tune by ear. Calibrate your A4 from 430 to 450 Hz for period and ensemble work. Show or hide octave numbers; prefer flats or sharps - your call. DESIGNED TO BE A JOY A focused, beautiful interface that gets out of your way. No ads interrupting your tuning session. Tune entirely offline. SPEAKS YOUR LANGUAGE Fully available in English, German, French, Italian, Chinese (Simplified), and Chinese (Traditional). Whether you play a Celtic lever harp at home or a concert pedal harp on stage, Harpie gets every string right.
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-reanimated
BUILD KIT DIFFICULTY
Advanced
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.
