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
Percentage Expert
Percentage Expert is ideal for everyday calculations as well as for business use
$9.99 · In-app purchases
PRICE
$9.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
N/A
No ratings yet
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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A product spec, screen plans, and build steps for your coding agent.
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What's included15 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 Percentage Expert: 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
Implement a more guided user flow with tooltips.
Assumption to check: Users often find it hard to navigate between calculation types.
Validate with people who use this workflow before building.
Hypothesis 2
Add settings to customize how results are shown.
Assumption to check: Limited customization options for results display.
Validate with people who use this workflow before building.
Hypothesis 3
Include a history feature to review past calculations.
Assumption to check: No history of calculations, making it hard to track progress.
Validate with people who use this workflow before building.
Hypothesis 4
Implement a language selection feature.
Assumption to check: Lack of support for multiple languages.
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
Percentage Expert is ideal for everyday calculations as well as for business use. With Percentage Expert you can do regular percentage calculations, process percentage increase or decrease, VAT calculations, find sale price, calculate percentage off and discounted price and much more. WHAT YOU CAN DO WITH PERCENTAGE EXPERT: • REGULAR PERCENTAGE: - find the percentage of a value (what is 8 percent of 250?) - find the initial value when you know the percentage and the sub-value (if 4 is 30%, what is the original number?) - find the proportion of one number to another number in percentage terms (20 is what percent of 150?) • PERCENTAGE CHANGE: Find the percentage change between two values, percentage of increase or decrease between the first value and the second one. The first number is considering as 100 percent. • ADD OR SUBTRACT A PERCENTAGE: You can add or subtract a percentage from a value • VAT CALCULATIONS: - calculate the price without VAT (net price). - calculate the price with VAT (gross price). - calculate the VAT amount. • FRACTION TO PERCENTAGE: Convert fractions to percentages and percentages to fractions. • DISCOUNT OR SALE PRICE: - calculate the discounted price and your saving - handle multiple discounts at one time - set discount as percentage or as value With Percentage Expert you can do percentage calculations based on various inputs including values, sub-values, percentages, ratios, fractions, percentage changes, percentage increase/decrease. If any two of values are entered, the percentage calculator finds the third one. For VAT calculations you may enter any VAT rate. Discount calculations: just enter the original price, discount, sales tax percentage (if applicable) and get the final price and the amount of money you save.You can enter discount percentage or discount amount. You can select rounding to the specified number of decimal places from 0 to 3. By default, the app displays 2 decimal places. To round results to the nearest whole number, select 0 decimal places. You can make calculations in one of 15 supported currencies. Use history tape to view recent calculations. Up to 25 entries are save in the history. Back and forward buttons lets you view your recent calculations. Easily share results or history with your friends or colleagues via email. Supports fractional values for numbers and percentages as well. You can calculate 7 1/8 percent from 300. To enter 7 1/8 just type 7_1/8 on the percentage expert keyboard Portrait and landscape mode.
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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.
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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.
