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
JustinGuitar Note Trainer
Most guitar players never properly learn the notes on the fretboard
$4.99 · In-app purchases
PRICE
$4.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 5.0
3 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 included16 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 JustinGuitar Note Trainer: map the core Education 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
Implement a personalized recommendation system based on user progress.
Assumption to check: Users struggle with finding exercises that suit their skill level.
Validate with people who use this workflow before building.
Hypothesis 2
Incorporate real-time feedback and tips.
Assumption to check: Limited feedback during exercises can lead to frustration.
Validate with people who use this workflow before building.
Hypothesis 3
Enhance the progress dashboard with more detailed analytics.
Assumption to check: Users may find it difficult to track their progress over time.
Validate with people who use this workflow before building.
Hypothesis 4
Add gamification elements like challenges, rewards, and levels.
Assumption to check: The app may not motivate users enough to practice regularly.
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
Most guitar players never properly learn the notes on the fretboard. We memorize shapes and guess—and it works for a while. But when we try to improve, we hit a wall. JustinGuitar Note Trainer helps us learn the fretboard fast, in just 5 minutes a day. No diagrams. No memorizing charts. Just simple exercises that build a real understanding of the guitar neck. We learn to find any note on the guitar fretboard, build a clear mental map across all strings, and stop guessing and actually know the notes. Short daily exercises perfect for busy schedules, smart repetition to reinforce weak spots, and practice anywhere with your phone. If we want to learn guitar notes properly, this is one of the most valuable skills we can build. Built by JustinGuitar.
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
TypeScript
React Navigation
Redux
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.
