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
ModWheels
ModWheels brings classical synthesizer modulation and pitch wheels to your iPhone and iPod
$1.99 · In-app purchases
PRICE
$1.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.0
9 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 should your app do differently? Your note travels with the kit so your coding agent builds around your idea.
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 ModWheels: 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 effect library and allow user-generated effects.
Assumption to check: Limited sound modules and effects compared to competitors
Validate with people who use this workflow before building.
Hypothesis 2
Integrate social sharing to allow users to share tracks.
Assumption to check: No social sharing features
Validate with people who use this workflow before building.
Hypothesis 3
Enable track collaboration between users.
Assumption to check: Lack of collaborative features
Validate with people who use this workflow before building.
Hypothesis 4
Provide clearer explanations and benefits of in-app purchases.
Assumption to check: In-app purchases can be confusing
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
ModWheels brings classical synthesizer modulation and pitch wheels to your iPhone and iPod. Just hook up a MIDI interface and control any MIDI enabled synth or keyboard. In addition to the wheel interface this app also features a pitch ribbon / wheel combination as it could be found on some vintage synths. This app comes in handy when you are using one of these new organ keyboards which also feature synth sounds. But for some reason the designers have forgotten the performance controls? ModWheels help you using the full potential of those keyboards. ModWheels can be used with most MIDI hardware like LINE6 MIDI Mobilizer and it also supports MIDI over WIFI ModWheels has been rated „Killer App“ by the testers of Apps4iDevices
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 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.
