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.
Castro is a beautiful, full-featured podcast player that makes it easy to track and manage lots of podcasts at the same time
Free · 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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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 Castro: Podcast App & 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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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 discovery features for new podcasts
Validate with people who use this workflow before building.
Hypothesis 2
Assumption to check: Difficulties with podcast subscriptions management
Validate with people who use this workflow before building.
Hypothesis 3
Assumption to check: Inconsistent offline listening capabilities
Validate with people who use this workflow before building.
Hypothesis 4
Assumption to check: Limited playback controls
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.
Castro is a beautiful, full-featured podcast player that makes it easy to track and manage lots of podcasts at the same time. Only listen to the episodes you want and easily skip the rest, queue up hours of podcasts at a time and enjoy a seamless listening experience with carplay compatibility, chapter support, trim silence and much, much more! HOW IT WORKS 1. New episodes land in the NEW tab. Read their descriptions, add episodes you like to your QUEUE, and clear the rest. 2. Press play to listen to episodes from your QUEUE in order. Queued episodes are downloaded automatically. 3. Re-order your QUEUE to plan your next few hours of listening at any time. Browse your LIBRARY to review the back catalogue, quickly access starred shows, and see your listening history. Subscribing to a podcast is no longer a commitment to listen to every episode. You don’t have to manage a huge list of subscriptions or choose a few shows and miss the rest. WHY OUR USERS LOVE CASTRO • Drag and drop podcasts to plan your listening with Castro’s unique queue • An elegant dark mode and thoughtfully designed sleep timer offer the best in night time podcast listening. • CarPlay support makes it easy to pick up where you left off while driving. • Apple Watch app to control playback and select another episode from your queue. • Episode notifications include a summary of the episode to help you decide if it interests you. Play, queue or clear the episode directly from the notification without opening the app. CASTRO PLUS Castro Plus is an optional paid subscription available for $24.99/year (includes a one-week trial). Plus unlocks a range of advanced features: • Trim Silence — With this option on, the app will analyze audio as it plays to detect silent parts and accelerate those parts. Get through more episodes faster. • Enhance Voices improves the listening experience for many podcasts and makes it easier to hear in loud environments. Under the hood, Enhance Voices applies a dynamic compressor to increase volume just where it’s needed. • Sideloading: Import audio files directly, just by dropping them in iCloud Drive • Mono-Mix — Mixes a stereo podcast to mono, which makes it easier to hear podcasts that pan some guests on left/right channels. • Chapter Support: Artwork, Skipping & Pre-selection. • Custom settings per-podcast: Episode Limit, Trim Silence, Enhance Voices, Mono Mix, Skip Intros, Playback Speed. WHAT PEOPLE ARE SAYING “Castro 3 is an incredible app.” — The Sweet Setup “Castro 3 is everything Castro already was, but better.” — MacStories Castro 3 Is a Great Modern Podcast App” — Beautiful Pixels “Unlike other podcatchers, Castro's primary virtue is its simplicity and ease of use. The app combines sleek visual design with crystal clear audio.” — Tom’s Guide CASTRO PLUS SUBSCRIPTION TERMS Castro Plus costs $24.99 per year. Prices are in US dollars and may vary in countries other than the US. Castro Plus is charged to your iTunes Account at confirmation of purchase. It will renew on the day before the current subscription period ends. You can cancel auto-renewal any time from the Castro settings screen. You can switch between the two subscription periods after you pick one, but your trial period will end immediately if you do, so it's best to wait till your free week is over before changing. Subscription automatically renews unless auto-renew is turned off at least 24-hours before the end of the current period. Your account will be charged for renewal within 24-hours prior to the end of the current period. Subscriptions may be managed by the user and auto-renewal may be turned off by going to the user's Account Settings after purchase. Any unused portion of a free trial period, if offered, will be forfeited when the user purchases a subscription to that publication, where applicable. Privacy Policy & Terms of Use: https://castro.fm/privacy-policy
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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.