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
OffOf
A beautiful percentage calculator.
$0.99 · In-app purchases
PRICE
$0.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.6
11 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.
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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 included14 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 OffOf: map the core Utilities 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
Offer advanced graphs and trends for better analysis
Assumption to check: Limited historical data visualization options
Validate with people who use this workflow before building.
Hypothesis 2
Allow users to set multiple alerts based on different criteria
Assumption to check: No customization for alerts
Validate with people who use this workflow before building.
Hypothesis 3
Implement real-time updates with background fetching
Assumption to check: Requires manual refresh for current usage
Validate with people who use this workflow before building.
Hypothesis 4
Enhance UI/UX with modern design elements and animations
Assumption to check: Basic user interface design
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
A beautiful percentage calculator. OffOf helps you calculate to percentage OFF of a particular number, and the percentage OF a particular number. OffOf is NOT a full calculator. Your device already comes with a great calculator. OffOf is a Percentage Calculator ONLY. • 35% OFF Instantly know how much you're going to spend while shopping. What is the cost of that $18.99 t-shirt when its 35% off? OffOf makes it easy to calculate. Simply enter 35% as the "Percentage" and 18.99 as the "Amount" and OffOf will show you how much you'll be spending after the discount. • 16% OF What is 16% of 2,458? OffOf will get you that answer instantly. Just enter 16% as the "Percentage" and 2,458 as the "Amount" and you'll know right away. • Real, satisfying mechanical keyboard sounds • Delightful haptic feedback on button presses and more
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
react-navigation
@react-native-community/datetimepicker
react-native-svg
expo-notifications
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.
