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
Guitar Tuner!
An easy-to-use accurate audio/visual tuner for your guitar
$2.99 · In-app purchases
PRICE
$2.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.8
355 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 Guitar 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
Expand tuning options to include more instruments and custom tunings.
Assumption to check: Limited tuning modes compared to competitors.
Validate with people who use this workflow before building.
Hypothesis 2
Implement calibration settings for better sensitivity adjustments.
Assumption to check: Microphone sensitivity issues on some devices.
Validate with people who use this workflow before building.
Hypothesis 3
Add visual indicators for how close the pitch is to the target note.
Assumption to check: No visual feedback for tuning precision.
Validate with people who use this workflow before building.
Hypothesis 4
Allow users to download preset tunings for offline use.
Assumption to check: Lack of offline functionality.
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
An easy-to-use accurate audio/visual tuner for your guitar. Provides a simple interface to visually check whether the pitch for each string is low or high, and lets you "see" the pitch change as you wind/unwind the string tuning machines. Tuning has never been easier. Shows exactly how many cents (1/100ths of a semitone) a note is out-of-tune. - Extremely accurate - within 1 cent (1/100th of a semitone) of each note with sub-second response time. - Developed in Austin, Texas, the "Live Music Capital of the World". - Use the standard tuning E-A-D-G-B-E or one of many alternate tunings: regular tunings such as Minor Third, special tunings such Drop D, open tunings such Open C, lower tunings, higher tunings. - Adjust pitch incrementally from 400 to 480 Hz or up/down a half/full step from A440. (The International Organization for Standardization specifies the frequency for the note A in the treble stave as 440 Hz. ISO 16:1975). - Tap to hear an accurate note if tuning by ear instead of using visual tuning. - Enable/disable Auto-string-detect (not recommended for noisy environments).
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
react-navigation
expo-av
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.
