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
Fitness Calc for Marines
Most full featured app for performing the Marine IST, PRT, CFT, and Body Composition (WHtR and Taping) analysis for Marines hands down.
$0.99 · In-app purchases
PRICE
$0.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.5
17 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.
Build your own version
Build Kit
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A product spec, screen plans, and build steps for your coding agent.
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Make it yours Optional
What should your app do differently? Your note travels with the kit so your coding agent builds around your idea.
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/
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 Fitness Calc for Marines: map the core Health & Fitness 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
Expand calculator options and allow user submissions.
Assumption to check: Limited calculators available
Validate with people who use this workflow before building.
Hypothesis 2
Implement modern UI components and animations.
Assumption to check: UI may feel outdated
Validate with people who use this workflow before building.
Hypothesis 3
Introduce community features for sharing results and challenges.
Assumption to check: Lack of social features
Validate with people who use this workflow before building.
Hypothesis 4
Provide better explanations of premium features during onboarding.
Assumption to check: In-app purchase clarity
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
Most full featured app for performing the Marine IST, PRT, CFT, and Body Composition (WHtR and Taping) analysis for Marines hands down. - In full compliance with Marine Corps Orders 6110.3A W ADMIN CH-4 and 6100.13A CH-4 in addition to latest MARADMINs 066/26 and 615/25. - Full support for Initial Strength Test (Enlisted, non-combat MOS) - Full support for Physical Fitness Test (run, row, plank, pull-ups, push-ups) with ability to email results - Full support for Combat Fitness Test with ability to email results - Altitude correction applied for both PRT and CFT aerobic tests - Overall PRT and CFT classification determined - Full body composition support * Waist-to-Height Ratio (WHtR) * Body Fat Assessment taping method - Performance (standard levels of performance) charts provided for each event and customized based on user input (gender, age, altitude) - All length measurement inputs via intuitive inch and eight-of-an-inch increments (like provided by a tape measure) - All measurements have proper rounding applied per the instructions - Links to official Marine Corps instructions - Ability to save and view past assessment results to see trends over time *** For quick responses, contact the developer via the App Info icon for any issues or feedback. *** *** NOTE: Per 10 U.S.C. 7881, this application and the application description below do not suggest that the use of the phrases "Marine Corps" and "Marines" is approved, endorsed, or authorized by the United States Marine Corps or any other component of the United States Department of Defense. These terms are used to ensure the proper target audience (e.g., future, current, or past members of the United States Marine Corps) can find and use this application. Per 32 CFR 765.14, the use of the common phrases "Marine Corps" and "Marines" does not imply any official or unofficial connection between the United States Marine Corps and the developer of this application or that the United States Marine Corps or the United States is in any way responsible for any financial or legal obligation of the developer. ***
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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
React Navigation
Zustand
React Native Paper
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.
