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
OneCalc+ All-in-one Calculator
This is the premium (ad-free) version of "All-in-one calculator" app for iOS.
$3.99 · In-app purchases
PRICE
$3.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.7
516 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.
Build your own version
Build Kit
Make this idea yours
A product spec, screen plans, and build steps for your coding agent.
First kit free with a verified email
Add to a Remix
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 OneCalc+ All-in-one Calculator: map the core Productivity 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 customize themes and button layouts.
Assumption to check: Limited customization options for users
Validate with people who use this workflow before building.
Hypothesis 2
Provide a tutorial or guided onboarding.
Assumption to check: Can be confusing for new users with many features
Validate with people who use this workflow before building.
Hypothesis 3
Incorporate more advanced graphing capabilities and function support.
Assumption to check: Lack of advanced graphing features
Validate with people who use this workflow before building.
Hypothesis 4
Implement a way to organize or categorize history for easier access.
Assumption to check: History can get cluttered
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
This is the premium (ad-free) version of "All-in-one calculator" app for iOS. All-in-one calculator is a must have calculator app for your iPhone and iPad. It features over 40 calculators and unit converters for everyday use, grouped under finance, everyday math, health, construction, date & time, unit converters, and shopping/ retail. Simple yet powerful, the following features are built into this all-in-one calculator:- STANDARD CALCULATOR • Includes percent key, negative sign, brackets and history viewer. • Advanced mode includes memory keys and functions for trigonometry, roots, exponents and logarithm found in scientific calculators. UNIT CONVERTER • Supports temperature, length, weight, area, volume and many more measurement units. • Currency converter. FINANCIAL CALCULATOR • Interest calculators using simple and compound interest • Loan repayment and amortization schedule. • Savings calculator with financial goal planner FRACTIONS/ PERCENTAGE CALCULATOR • Calculators for 3-way percentage, discount pricing, profit margin, tax, tip & split bill. • Add, subtract, multiply, divide fractions HEALTH • BMI and calorie calculators to help you keep track of your body weight. CONSTRUCTION CALCULATOR • Calculators to estimate cement, sand, gravel quantities for concrete blocks, wall plastering and brick works. • Area and volume calculator for common geometric shapes. • Irregular land area calculator • Solve height and distance problems using right-triangle calculator. LIFESTYLE • Age and date calculator Need to know what you are paying for? Try out the free version of this calculator app from the developer profile.
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
AsyncStorage
react-native-reanimated
react-native-svg
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.
