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
McRun
** Runner's World selected McRun "Must Have Running Apps - Top Tool"
$4.99 · In-app purchases
PRICE
$4.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.2
145 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.
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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Combine features and design from your favorite apps.
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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 McRun: 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
Integrate social challenges and leaderboard functionality.
Assumption to check: Limited social features for competition and motivation.
Validate with people who use this workflow before building.
Hypothesis 2
Offer tailored workout plans based on user goals.
Assumption to check: Lack of personalized workout plans.
Validate with people who use this workflow before building.
Hypothesis 3
Simplify navigation and enhance UI clarity.
Assumption to check: User interface can feel cluttered.
Validate with people who use this workflow before building.
Hypothesis 4
Improve integration with HealthKit and Google Fit.
Assumption to check: Inconsistent syncing with health devices.
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
** Runner's World selected McRun "Must Have Running Apps - Top Tool" McRun is the official app version of the well-known McMillan Running Calculator. Created by internationally recognized coach Greg McMillan, this calculator allows you to compute your running potential across different distances. You only need to input your best time from one distance and McRun does the rest. The app will tell you how fast you are capable of running from 100 yards to 100 miles. It also suggests optimal training paces based on both your fitness level and the type of runner you are. McRun is a great way to target and train for peak performance. Feedback? Suggestions? Sore legs? Send us an email: [email protected] Quick start guide: - From Calculator screen enter your best time in any distance and press “calculate” - View your equivalent race times - Press “Workout Paces” to see recommended paces for tempo runs, long runs, easy runs, and speed workouts - Select “Recalculate” to return to the Calculator screen - Turn your iPhone sideways to see motivational quotes and training tips
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
TypeScript
Supabase
React Navigation
Expo Sensors
BUILD KIT DIFFICULTY
Starter
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.
