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
Podcast App & Player - Castbox
The best podcast app & podcast player to find, save, download, and listen to your favorite podcasts, FM, and audiobooks.
Free · In-app purchases
PRICE
Free
In-app purchases
BUSINESS MODEL
Freemium
No overall Grossing estimate available
RATING
★ 4.9
199,347 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 included19 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 Podcast App & Player - Castbox: 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 caching for downloaded episodes
Assumption to check: Limited offline capabilities for listening
Validate with people who use this workflow before building.
Hypothesis 2
Enhance search and recommendation algorithms based on user behavior
Assumption to check: Difficulty in discovering new podcasts
Validate with people who use this workflow before building.
Hypothesis 3
Simplify the library view with better categorization and filtering options
Assumption to check: Cluttered user interface for managing subscriptions
Validate with people who use this workflow before building.
Hypothesis 4
Standardize playback controls across all screens for a smoother experience
Assumption to check: Inconsistent playback controls
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
The best podcast app & podcast player to find, save, download, and listen to your favorite podcasts, FM, and audiobooks. Access over 95 million audio content including podcasts, audiobooks, FM radio, white noise/fan noise, guided meditation podcasts from 27 different countries. Download Castbox and turn your iPhone or iPad into a fully functional podcast player. You would be able to control the playback on your apple watch, switch to the next episodes using CarPlay, or meditate to the guided meditation podcasts with your Apple HomePod, Amazon Alexa. Discover popular podcasts on various topics, including: - TV Series podcasts: Binge Mode: Game of Thrones, Game of Thrones The Podcast, History of Westeros (Game of Thrones), Game of Thrones LIVE; - News & Politics podcasts: CNN 10, NPR News Now, Fox News Radio Newscast, The Overcast by The Seattle Times; - Music-related podcasts: Dissect from Cole Cuchna & Spotify Studios, Defected Radio, Capital FM; - Games & Hobbies podcasts: Wolverine: The Lost Trail from Stitcher; - Sports podcasts: The Ringer MLB Show, MLB Network, The Chicago Audible; - Technology podcasts: The Overcast Podcast, This Week in Google, Google Cloud Platform Podcasts; - Talk Shows: Sincerely, X from TED and Audible, By The Book from Stitcher, Luminary from Luminary.fm; - Business podcast:s Youpreneur FM Podcast; - Sleep: Sleep With Me, Guided Sleep Meditations, Sleep and Relax ASMR - Popular shows: SiriusXM Entertainment, Waze, WazeOut Radio Super intuitive and easy-to-use podcast app & podcast player for iPhone with： - Personalized podcast recommendations according to your podcast list - A powerful search engine that allows you to find your favorite podcasts effortlessly - Smooth streaming and downloading of podcasts, radio, FM, and audiobooks - The convenient Widget for you to continue enjoying the podcasts easily - Smart speakers supported, including Apple HomePod, Amazon Alexa - Fully support cross-device syncing for iPhone/iPad/Apple Watch/Google Devices - Daily top podcasts list - One-click subscription and never miss an episode for every podcast - Sleep timer to fall asleep soundly - Adjust playback speed during the podcast to accommodate your listening habits - Volume Boost - Trim Silence - CarPlay Support - Podcast Community - Import your favorite podcasts with OPML from Google podcast, Overcast, iHeartradio, Pocket Casts, Podbean, Podcast Addict, Spotify, Stitcher, the Podcast app, Tunein, and apple podcast app! - Join the millions experiencing better bedtime, lower stress, and less anxiety with Zen mode! Privacy policy: https://castbox.fm/policy.html Terms of use: https://castbox.fm/termsofservice.html Love Castbox? Like us on Facebook: https://www.facebook.com/castbox.fm Follow us on Twitter: https://twitter.com/CastBox_FM
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
Axios
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.
