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
PepCalc: Peptide Calculator
PepCalc: The top-rated peptide calculator app! As featured on leading podcasts including Ben Greenfield, Data Driven Radio, and more.
$9.99 · In-app purchases
PRICE
$9.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.8
950 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'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 PepCalc: Peptide Calculator: 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
Implement input validation and suggestions for peptide sequences.
Assumption to check: Users find the input fields can be confusing for complex sequences
Validate with people who use this workflow before building.
Hypothesis 2
Add edit and delete functionality for calculation history.
Assumption to check: Limited history tracking features
Validate with people who use this workflow before building.
Hypothesis 3
Integrate sharing features to allow users to share their calculations with others.
Assumption to check: No social sharing options
Validate with people who use this workflow before building.
Hypothesis 4
Enhance the purchase flow with clear descriptions and benefits of premium features.
Assumption to check: In-app purchase process is not clear
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
PepCalc: The top-rated peptide calculator app! As featured on leading podcasts including Ben Greenfield, Data Driven Radio, and more. PepCalc is a mathematical utility for laboratory researchers and scientists. It provides a digital interface for solving complex reconstitution ratios in educational settings. Stop the guesswork! PepCalc is the simplest way to get peptide reconstitution right. Instant per unit or tick mark results, saved protocols for repeatable calculations, multi-peptide blend support, and smart conversions. Download PepCalc and get answers in seconds. How it works: 1. Enter your peptide amounts and water volume. 2. Choose your units and tick marks. 3. See instant results. Features: FLEXIBLE INPUTS: Set peptide amounts, water volume, units and tick marks, and target amount. PRESETS: Choose 100-unit or 40-unit scales for fast setup, or use fully custom inputs for any volume. MULTI-PEPTIDE BLENDS: Add unlimited peptides to a single volume and calculate each automatically for complex research. SMART CONVERSIONS: Instantly switch between mcg, mg, and g without re-entering data. SAVED PROTOCOLS: Save favorite calculations with names and notes for fast recall. No more retyping. PROTOCOL SHARING AND IMPORT: Create and share beautiful protocol images directly via social media, chat, and email that other PepCalc users can import directly via link or QR code. THEMES: Multiple themes with light and dark mode support to suit everyone's preferences. PRIVATE BY DESIGN: No signup required. No ads. Your data remains on your device. DISCLAIMER: PepCalc is for research and educational purposes only. Not for medical use. This app does not provide medical advice.
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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
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.
