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
Alt: Buy & Sell Cards
Alt is the modern marketplace to buy and sell trading cards
Free · In-app purchases
PRICE
Free
In-app purchases
BUSINESS MODEL
Freemium
No overall Grossing estimate available
RATING
★ 4.9
13,335 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 should your app do differently? Your note travels with the kit so your coding agent builds around your idea.
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/
Preview a sample Build Kit No email needed
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 Alt: Buy & Sell Cards: map the core Sports 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 lower transaction fees or rewards for frequent sellers.
Assumption to check: High fees for sellers.
Validate with people who use this workflow before building.
Hypothesis 2
Include more payment methods like cryptocurrency.
Assumption to check: Limited payment options.
Validate with people who use this workflow before building.
Hypothesis 3
Enhance search functionality with advanced filters.
Assumption to check: Difficult to filter/search cards.
Validate with people who use this workflow before building.
Hypothesis 4
Implement robust user verification to build trust.
Assumption to check: User verification issues.
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
Alt is the modern marketplace to buy and sell trading cards. Built by collectors, for collectors, Alt offers a 24/7 auction and fixed price marketplace, the best cash advance program in the hobby, detailed data and card values, and the ability to manage your collection - all from the mobile app. Join our community and experience a new way to buy and sell cards. Sellers - Only 14-day continuous auction in the hobby - giving your cards maximum visibility. - Largest and quickest cash advances in the industry. - Competitive selling fees and fast payouts. Buyers - Bid in our bi-weekly Liquid Auctions or buy from our Fixed Price Marketplace. - Compete in the most exciting extended bidding experience in the hobby. - View past auction sales, card values, and data trends straight from the app. - Easily save your searches so you never miss a card. Cash Advances - The most competitive cash advances in the hobby. Period.
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
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BUILD KIT DIFFICULTY
Expert
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.
