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
Super Slow Downer
Super Slow Downer allows you to slow the play of music while maintaining pitch.
$0.99 · In-app purchases
PRICE
$0.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.5
25 ratings · Top 15%
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 Super Slow Downer: 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
Implement an advanced algorithm to maintain audio quality while slowing down.
Assumption to check: Users often find audio quality degradation at lower speeds.
Validate with people who use this workflow before building.
Hypothesis 2
Support a wider range of audio file types and streaming options.
Assumption to check: Limited audio formats supported.
Validate with people who use this workflow before building.
Hypothesis 3
Simplify the payment flow and provide clearer subscription benefits.
Assumption to check: In-app purchase process can be confusing.
Validate with people who use this workflow before building.
Hypothesis 4
Introduce offline downloads for saved tracks.
Assumption to check: No offline playback option.
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
Super Slow Downer allows you to slow the play of music while maintaining pitch. Super Slow Downer allows you to play songs in a loop at a slower speed. It's great for musicians trying to learn new songs. You can select any part of a song to repeat at normal speed. You can also slow the song down or even speed it up by changing the speed between 25% (0.25X) and 200% (2X speed). The pitch remains the same as you change speed. As an option, you can separately adjust the pitch in addition to the speed. If you want to change the key the song is in, you can do so in the app. Setup loops by touching the "loop" button during playback. You can load music files that are saved on your iCloud Drive or select music files on your device's music library (owned music appearing in the Music app). This app does not support Apple Music streaming music or Spotify streaming music. Super Slow Downer is a great app musicians, music transcribers or dancers wanting a tool to make their practices better.
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
expo-av
axios
react-navigation
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.
