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
String Position Pro
String Position Pro is a flashcard app and complete offline practice toolkit for violin, viola, cello, and double bass
$4.99 · In-app purchases
PRICE
$4.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 5.0
1 ratings · Top 5%
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 included17 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 String Position Pro: 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
Expand to include more string instruments and custom tunings.
Assumption to check: Limited instrument options for tuning
Validate with people who use this workflow before building.
Hypothesis 2
Implement visual guides or animations to show users how close they are to the correct pitch.
Assumption to check: Lack of visual feedback for pitch accuracy
Validate with people who use this workflow before building.
Hypothesis 3
Add social sharing options for users to share their tunings or progress.
Assumption to check: No community or sharing features
Validate with people who use this workflow before building.
Hypothesis 4
Offer a freemium model with basic features included for free.
Assumption to check: Subscription costs may deter 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
String Position Pro is a flashcard app and complete offline practice toolkit for violin, viola, cello, and double bass. It is designed to support students, teachers, and parents alike, offering engaging tools and feedback mechanisms that make practice more effective and enjoyable. String Position Pro works entirely offline and contains no ads, subscriptions, in-app purchases, or data collection. It was developed by Lachlan Dent, who holds PhD (Music Performance), Master of Music (Performance), and Master of Teaching degrees, in collaboration with other professional string teachers and performers. Features: Flashcards for note recognition and fingerboard mapping, interactive fingerboard charts with high-quality recordings, drones (long tones for intonation practice), a key signature explorer, scale helper (play your instrument and receive real-time feedback), scale builders (learn the notes of the scales before you play them), scale mappers (explore scales and arpeggios across the fingerboard and choose valid fingerings), an interval explorer, a practice log, tuners designed specifically for strings, and a metronome. It also features 'listening' flashcards with tuning support, so you can play your answer on your instrument (violin, viola, and cello supported). Flashcard features: Violin and Double Bass: Comprehensive note-reading and position practice. Viola: Alto and treble clef levels tailored for your instrument. Cello: Bass, tenor, and treble clef levels, from half position through fourth position. Audio reinforcement: Real note recordings help you connect what you see with what you hear. Support for A440hz to A444hz. English note names (ABC), Fixed Do Solfege (Do Re Mi), and German notes (AHC) modes supported. General knowledge quiz for music terms and markings, focused on those seen most often by string players. Download String Position Pro now and maximise the value of your music lessons!
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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
Zustand
react-navigation
expo-sound
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.
