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
4APP Sports
45,000+ players trust 4APP to throw harder, walk fewer batters, and stay healthy while doing it.
Free · In-app purchases
PRICE
Free
In-app purchases
BUSINESS MODEL
Freemium
No overall Grossing estimate available
RATING
★ 4.4
198 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 included18 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 4APP Sports: 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
Enhance tracking with detailed analytics and comparisons.
Assumption to check: Limited athlete tracking features compared to competitors
Validate with people who use this workflow before building.
Hypothesis 2
Simplify layout for better user experience.
Assumption to check: User interface can feel cluttered
Validate with people who use this workflow before building.
Hypothesis 3
Offer clear explanations of premium features and value.
Assumption to check: In-app purchases may confuse users
Validate with people who use this workflow before building.
Hypothesis 4
Add social sharing and community features for engagement.
Assumption to check: Lack of social 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
45,000+ players trust 4APP to throw harder, walk fewer batters, and stay healthy while doing it. - 93% improve command - 87% gain velocity - 60% feel healthier - 40% gain 5+ mph in just 30 days Created by Cy Young Award winner Trevor Bauer, the Ultimate Pitching Program helps pitchers dramatically improve their game: - Struggling to throw harder? - Can’t hit your spots? - Losing stamina late in games? - Battling constant injuries? - Trying to stand out to scouts? - Having trouble recovering after a game? Whether you’re chasing a spot on a new team, aiming to impress college recruiters, or simply looking to enjoy the game more, 4APP Sports has the tools you need to succeed. - Custom Remote Training tailored to your goals and needs - Pitching Mechanics Video Analysis by the pros - Daily Throwing Programs for consistent progress - Command-Tracking Tools to master the strike zone - Daily Health Tracking for optimal recovery and peak performance - Hitter Attack Plans to dominate every at-bat - Pitching Journals to track your growth Subscription Tiers for Every Pitcher Pitching Lite: - Health Tracking - Command Tracking + Bullpen Coach - Pitching Journal Pitching Essentials: - Health Tracking + In-Depth Insights from Pro Coaches - Command Tracking + Pro Bullpen Coach - Hitter Attack Plans and Heat Maps - Pitching Journal Ultimate Pitching Program: - Fully Customized Training - Monthly Throwing Programs - Exclusive Video Content Library - Health Tracking + In-Depth Insights from Pro Coaches - Command Tracking + Pro Bullpen Coach - Hitter Attack Plans and Heat Maps - Pitching Journal 4APP Sports is redefining the way pitchers train and recover. Used by pitchers at every level—from T-Ball to the Big Leagues—4APP provides the tools, insights, and guidance to help you unlock your full potential. What are you waiting for? Join thousands of pitchers already transforming their game. Download 4APP Sports today and start your journey to the top of the mound! Terms of Use: https://www.4appsports.com/terms
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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
Supabase
Zustand
React Navigation
Axios
BUILD KIT DIFFICULTY
Intermediate
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.
