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
Theory Lessons
Theory Lessons features 39 music theory lessons from musictheory.net, presented in their original animated versions.
$2.99 · In-app purchases
PRICE
$2.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.4
127 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 included18 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 Theory Lessons: 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 lesson library and add advanced content.
Assumption to check: Limited lesson variety and depth
Validate with people who use this workflow before building.
Hypothesis 2
Simplify subscription model and clarify benefits.
Assumption to check: In-app purchase confusion
Validate with people who use this workflow before building.
Hypothesis 3
Add a visual progress tracking system for users.
Assumption to check: No progress tracking features
Validate with people who use this workflow before building.
Hypothesis 4
Incorporate various exercise types to engage users more.
Assumption to check: Lack of interactive exercises
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
Theory Lessons features 39 music theory lessons from musictheory.net, presented in their original animated versions. Complete lesson list: • The Staff, Clefs, and Ledger Lines • Note Duration • Measures and Time Signature • Rest Duration • Dots and Ties • Steps and Accidentals • Simple and Compound Meter • Odd Meter • The Major Scale • The Minor Scales • Scale Degrees • Key Signatures • Key Signature Calculation • Generic Intervals • Specific Intervals • Writing Intervals • Interval Inversion • Introduction to Chords • Triad Inversion • Seventh Chords • More Seventh Chords • Seventh Chord Inversion • Diatonic Triads • Roman Numeral Analysis: Triads • Diatonic Seventh Chords • Roman Numeral Analysis: Seventh Chords • Composing with Minor Scales • Voicing Chords • Analysis: O Canada • Nonharmonic Tones • Phrases and Cadences • Circle Progressions • Common Chord Progressions • Triads in First Inversion • Triads in Second Inversion • Analysis: Auld Lang Syne • Building Neapolitan Chords • Using Neapolitan Chords • Analysis: Moonlight Sonata
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
Supabase
Zustand
react-native-reanimated
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.
