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
Happ - Proxy Utility
Important Notice
Free · In-app purchases
PRICE
Free
In-app purchases
BUSINESS MODEL
Freemium
No overall Grossing estimate available
RATING
★ 4.6
14,499 ratings · Top 15%
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 Happ - Proxy Utility: map the core Utilities 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
Offer a wider selection of proxies and allow user suggestions.
Assumption to check: Limited proxy options compared to competitors
Validate with people who use this workflow before building.
Hypothesis 2
Simplify settings with guided onboarding or tutorials.
Assumption to check: Complicated settings for new users
Validate with people who use this workflow before building.
Hypothesis 3
Implement a favorites feature for quick access.
Assumption to check: No ability to save favorite proxies
Validate with people who use this workflow before building.
Hypothesis 4
Provide more insights and analytics on connections and performance.
Assumption to check: Lack of detailed connection logs
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
Important Notice Happ does not sell or provide VPN services. Beware of scammers claiming to offer “official Happ VPNs” — they are not affiliated with us. Users must set up their own servers and follow local laws when using the app. Happ is a mobile app that makes using proxy and vpn servers easy, offering a user-friendly interface and useful features. Main functionalities include: Configuration of proxies based on rules. Support for multiple protocol types. Hidden subscriptions. Encrypted subscriptions. Protocols supported are: VLESS(Reality) VMess Trojan Shadowsocks Socks Hysteria2 Happ ensures your network activity remains private by not collecting any data; your information remains solely on your device without being sent to external servers. It's important to highlight that Happ does not provide VPN services for purchase. Users are responsible for acquiring or setting up their own servers. Users should also comply with applicable laws in their jurisdiction when utilizing the app.
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
Zustand
Axios
React Navigation
Expo Notifications
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.
