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
Lark Player: Offline Music
Lark Player is a stylish and free offline music player and video player for iPhone
Free · In-app purchases
PRICE
Free
In-app purchases
BUSINESS MODEL
Freemium
No overall Grossing estimate available
RATING
★ 4.2
112 ratings · Top 30%
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 Lark Player: Offline Music: 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 better sorting and filtering options for offline music.
Assumption to check: Limited offline music management features
Validate with people who use this workflow before building.
Hypothesis 2
Enhance audio quality settings for better user control.
Assumption to check: Inconsistent playback quality
Validate with people who use this workflow before building.
Hypothesis 3
Simplify the subscription process and provide clearer options.
Assumption to check: Complicated subscription management
Validate with people who use this workflow before building.
Hypothesis 4
Integrate social media sharing for tracks and playlists.
Assumption to check: Limited 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
Lark Player is a stylish and free offline music player and video player for iPhone. It supports to play all major formats of offline music and videos. This free music player has a powerful playlist and the best user interface. It also supports file import on the device, such as Album and Files. Even import your music files via Wifi and cloud drive. Currently, more than 100 million users worldwide use Lark Player to play music offline. Audio Player and Video Player Support to All popular formats Not only an MP3 player, it supported audio formats including: MP3, WAV, FLAC, AAC, M4A, ACC ,etc. Not only an audio player, it is also a video player. With this media player you can play video that formats of MP4, 3GP, MOV, MKV, etc. Easily Manage Your Files You can browse your offline music by song, artist, album, genre, and more with this free offline music player. It also supports to create and manage music playlists. More Free Features: Offline music player, songs player, audio player, mp3 player with high quality music experience. Audio player support audio formats like MP3, WAV, FLAC, AAC, M4A, ACC ,etc. Video player support to video formats like MP4, 3GP, MKV, etc. Save your favorite songs and play them in offline music player without wifi. Play song in shuffle, order or loop with the MP3 player. Play music in background and notification bar with the MP3 player. Browse and play music by albums, artists, music playlists, genres, etc. If you have any audio files or video files, just play it with Lark Player Note: Lark Player is an offline music player and offline video player. It’s not a music downloader and it doesn't support music download. Follow our social media to get more music information： Facebook: https://www.facebook.com/larkplayerofficial Instagram: https://www.instagram.com/larkplayerbrasil/ Hope you enjoy music and have a good time at Lark Player! If you have any suggestions or face any problem while using the app, please send your feedback to [email protected]
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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
Zustand
React Navigation
expo-av
@react-native-async-storage/async-storage
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.
