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.
SLOW DOWN AND SPEED UP ANY SONG
$4.99 · In-app purchases
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.
A product spec, screen plans, and build steps for your coding agent.
First kit free with a verified email
Combine features and design from your favorite apps.
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Generating… usually about a minute.
What should your app do differently? Your note travels with the kit so your coding agent builds around your idea.
A product spec, phased build plan, differentiation notes, and screen references.
Illustrative example: an invoice app for independent contractors. Your kit is tailored to the app you choose; this is not its generated content.
Goal: Send a clear invoice after finishing a job.
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.
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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Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.
Rork plan preview for Grooves: Song Speed Changer: 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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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
Assumption to check: Limited features compared to professional DAWs
Validate with people who use this workflow before building.
Hypothesis 2
Assumption to check: Inconsistent audio playback quality
Validate with people who use this workflow before building.
Hypothesis 3
Assumption to check: User interface can be cluttered
Validate with people who use this workflow before building.
Hypothesis 4
Assumption to check: No social features for sharing sessions
Validate with people who use this workflow before building.
Original App Store material. Ratings and screenshots describe the existing app, not proof of demand for your version.
SLOW DOWN AND SPEED UP ANY SONG Maybe you’re trying to learn a tricky guitar riff or figure out a new dance routine. Or maybe you want to change the speed of your favourite tracks to lock into the rhythm of your fitness workout. Grooves lets you continuously adjust the speed of any song in the Apple Music catalog, in your iPhone Music Library or Files app to a speed that’s right for you. PICK ANY SONG • Change the tempo of any song on Apple Music, in your Music app or Files app without affecting pitch or fidelity • Access the entire Apple Music catalog of over 100 million songs! • Play tracks from the Files app, including on Cloud Drive, Dropbox and other cloud services • Quick access to your recently played songs ADJUST THE TEMPO • A simple slider for adjusting tempo • Select any tempo from -50% to +100%, in 1% increments • Easily revert to the original tempo with just one tap • Grooves will remember your chosen tempo until you want to adjust it again CREATE SETLISTS • Create unlimited Setlists • Continuous play from one song to the next • Set and remember different tempos for different songs • Combine songs from Apple Music, your Music app and Files app all in the same Setlist • Create Setlists from existing albums and playlists in your Music app or on Apple Music REPEAT JUST ONE SECTION • Select a section of a song and then loop it to make practise easy • Add sections of a song to a Setlist multiple times and then play them back at different tempos APPLE WATCH • Easily control playback, tempo and volume from your wrist AIRPLAY • AirPlay support for output to wireless speakers or Apple TV AND MORE.. • Change the key (transpose up or down) of locally stored DRM-free songs imported into the app or from your Music app. (Missing the pitch controls from the last version? Re-enable them in the Settings app > Grooves. Then swipe left on the album artwork when playing a song) IMPORTANT NOTE! * Songs from streaming services other than Apple Music are not supported *
Written user reviews are not shown here. Check current App Store reviews >
Plan a focused first version with your coding agent. These are planning assumptions, not a delivery guarantee.
Choose one audience and one core workflow. Use the kit to agree on its screens, data, and acceptance criteria before building.
Decide which secondary features, integrations, and platform support can wait. Your version does not need to reproduce everything in the original.
Validate external services, specialist technology, data access, and ongoing costs for your chosen scope.
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.