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
CastKeeper: Podcast Player
CastKeeper: Your Podcasts
$2.99 · In-app purchases
PRICE
$2.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 5.0
2 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 included17 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 CastKeeper: Podcast Player: map the core News 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 robust offline downloads for episodes.
Assumption to check: Limited offline functionality for podcast episodes
Validate with people who use this workflow before building.
Hypothesis 2
Enhance search and categorization features for better discovery.
Assumption to check: Difficult to discover new podcasts
Validate with people who use this workflow before building.
Hypothesis 3
Include playback speed controls for user preference.
Assumption to check: No customizable playback speed options
Validate with people who use this workflow before building.
Hypothesis 4
Add share buttons for episodes and podcasts.
Assumption to check: Lacks social sharing features
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
CastKeeper: Your Podcasts. Yours Forever. Featured in Podnews, The Virginian-Pilot, Daily Press, Hampton Roads Business Journal, and loved by users across the world. Some people collect vinyl. Some collect baseball cards. You collect podcasts — let's keep it that way. Episodes get pulled. Shows move. Feeds vanish. If you love a podcast, you should be able to keep it. Forever. Archive audio and video podcasts, transcripts, chapters, artwork, notes, and metadata to storage you control: iCloud Drive Dropbox External USB drives S3-compatible storage Your own cloud When someone says "Sorry, that episode isn't available anymore," you can politely smile… and press Play. Meet SmartKeep SmartKeep is CastKeeper's fully automatic archiver. Enable it on any subscribed show, pick a storage destination, and let it run — zero effort, full sync across your devices. Love an episode? Lock it and it stays forever (everything you archive manually is locked by default, too). SmartKeep is included with your one-time purchase. No subscriptions, ever. We Mind Our Own Business Some apps know everything you listen to. CastKeeper would rather not. No account. No ads. No subscriptions. No creepy tracking. Tracking Prevention cuts podcast analytics requests, because your podcast player shouldn't have a side hustle. Listen Smarter AI summaries Smart chapters Searchable transcripts Live Captions Episode translation Timestamped notes Powerful search It's almost unfair to the pause button. A Podcast Player That Actually Plays Podcasts Audio and video playback, CarPlay, Picture in Picture, Mini Player, Sleep Timer, and private sync across iPhone, iPad, and Mac. Everything you'd expect — plus the part where your library doesn't randomly evaporate. Built for Everyone VoiceOver, Dynamic Type with dyslexia-friendly fonts, Live Captions, keyboard navigation, high-contrast display, and accessibility features throughout. Buy It Once No "Premium." No "Premium Plus." No "Premium Ultra Max Podcast Infinity." Just CastKeeper — a one-time purchase for all your devices, including Family Sharing. Your podcasts. Yours forever.
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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
BUILD KIT DIFFICULTY
Advanced
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.
