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
Margin+ (Margin Calculator)
Are you ready to close the deal? Margin+ is the iOS application designed to get you to the handshake more quickly.
$2.99 · In-app purchases
PRICE
$2.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.8
850 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 included17 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 Margin+ (Margin Calculator): map the core Finance 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
Allow users to view and manage more detailed calculation history.
Assumption to check: Limited calculation history visibility
Validate with people who use this workflow before building.
Hypothesis 2
Enable users to customize currency symbols and formats.
Assumption to check: No customization options for currency symbols
Validate with people who use this workflow before building.
Hypothesis 3
Add features for advanced margin analysis and reporting.
Assumption to check: Lack of advanced margin analysis features
Validate with people who use this workflow before building.
Hypothesis 4
Implement an export feature to save calculations as PDF or CSV.
Assumption to check: No export functionality for calculations
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
Are you ready to close the deal? Margin+ is the iOS application designed to get you to the handshake more quickly. Key Features: - Fast margin/markup calculator. - Discount and cost variance analysis built into workflow. - Apple Watch Support - World currency converter supporting over 150 world currencies. - Integrated calculator and large data entry keypad. - Currency conversion is fully integrated into you margin/markup analysis workflow. - 100% ad free. -- Fast Margin/Markup Calculator -- Margin+ is a sales tool for fast margin/markup analysis. A user-friendly sliding interface gives you all the information you need for lightning fast discount/cost analysis, taking you from quote to sale in a few simple steps. Margin+ provides a very elegant margin/markup analysis workflow. The first screen you are presented with is a simple margin or markup calculator. Enter in two components of Price, Cost, Margin/Markup or Gross Profit and Margin+ will calculator the other two numbers on the fly. Easily switch between margin and markup calculations. -- Discount and Cost Variance Analysis -- If you need to push beyond a simple margin/markup calculator, slide the interface from right to left to take your workflow to price discounts. Slide one more time to do cost variance analysis. Use the simple-to-use slider to lock in your discount or cost variance lightning fast. You can apply discounts and cost changes by % or by amount. As you make your changes, see how this impacts your final margin/markup. -- Apple Watch Support -- Mirror your margin and markup calculations from your phone to your watch. Edit values with the built in calculator and change currencies from the watch. See all your latest calculations from the Apple Watch Glance. -- World Currency Conversion -- Powerful world currency conversion is fully integrated into the app. With support for over 150 world currencies, Margin+ will enable you to deal with any situation. Margin+ takes this one step further by integrating the currency converter into the data entry calculator. If you want to type in US Dollars and have the converted amount in Euros populate the app, it can do this for you automatically. -- Copy and Paste Support -- Copy and Paste is fully supported inside of Margin+. You can even paste in values from other apps. Make the leap with JumpGap Software’s Margin+, the sales tool that puts the sale at your fingertips.
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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 Navigation
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Axios
React Native Async Storage
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.
