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.
MathU RPN is an advanced scientific and financial calculator designed in the spirit of classic HP calculators
$24.99 · In-app purchases
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.
A product spec, screen plans, and build steps for your coding agent.
First kit free with a verified email
Combine features and design from your favorite apps.
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Generating… usually about a minute.
What should your app do differently? Your note travels with the kit so your coding agent builds around your idea.
A product spec, phased build plan, differentiation notes, and screen references.
Illustrative example: an invoice app for independent contractors. Your kit is tailored to the app you choose; this is not its generated content.
Goal: Send a clear invoice after finishing a job.
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.
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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Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.
Rork plan preview for MathU RPN Calc: 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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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
Assumption to check: Users find it difficult to learn RPN (Reverse Polish Notation)
Validate with people who use this workflow before building.
Hypothesis 2
Assumption to check: Limited advanced features compared to competitors
Validate with people who use this workflow before building.
Hypothesis 3
Assumption to check: High price point for casual users
Validate with people who use this workflow before building.
Hypothesis 4
Assumption to check: Lack of customization options for the interface
Validate with people who use this workflow before building.
Original App Store material. Ratings and screenshots describe the existing app, not proof of demand for your version.
MathU RPN is an advanced scientific and financial calculator designed in the spirit of classic HP calculators. MathU RPN is based on the Reverse Polish Notation (RPN) entry system and combines more than 96 functions to create a calculator that meets the needs of professionals who use a calculator every day. First released in 2008, the calculator continues to be updated with new features as iOS improves. MathU RPN works on the iPhone, iPad and macOS. On the iPad, MathU RPN maintains its orientation as the iPad is turned and you can rotate it from portrait to landscape keypad layout via the Rotate button. When the iPad has a hardware keyboard attached, you can type of the names of the buttons the keyboard to execute them -- thus avoiding having to press the calculator keys with your finger. On the iPhone, you can lock it to always use the portrait or landscape keypad or let it switch orientations automatically when you rotate your phone. MathU RPN is an excellent financial calculator. There are functions for computing mortgage amortization and cash flow computations like IRR and NPV, as well as functions for working with dates. Many of the existing financial functions have been extended to handle odd periods (conforming to the same conventions as the HP-12C). In addition, on tall devices (like most iPhones), the financial registers are displayed on the keypad. MathU RPN is also a programmer's calculator. The A-F keys are available right up front for easy entry in HEX mode and there are many functions for working with integers. Dr. Clay M. Thompson of Creative Creek has harnessed the computational power of the iPhone to produce an accurate and high performance calculator. General Features - IEEE double precision accuracy (16 digits) - High performance fast computations - 20 storage registers - 5 financial registers - 16 high stack (switchable to 4) - Supports international number separators - Switch between portrait and landscape keypads - Quick access to the preference and on-line manual - Stack and Register view (accessible via [RCL][RCL] Scientific Features - Full set of trigonometric functions - Full set of logarithmic and power functions - Statistics functions - Polar and rectangular conversions - Repeated computations Mortgage and Loan Features - Time value of Money functions - Compute mortgage and loan terms - Solve for payments and interest rates - Solve for IRR and NPV - Date functions Computer Science Features - Number bases (HEX, OCT, DEC, BIN) - Bitwise logical operations - Masking and shifting functions - Support for a wordsizes up to 48 bits - Modular arithmetic MathU 4.1 supports iOS 16.6 or higher as well as macOS. For more info (including the users manual) go to http://www.creativecreek.com or use the built-in quick reference.
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Plan a focused first version with your coding agent. These are planning assumptions, not a delivery guarantee.
Choose one audience and one core workflow. Use the kit to agree on its screens, data, and acceptance criteria before building.
Decide which secondary features, integrations, and platform support can wait. Your version does not need to reproduce everything in the original.
Validate external services, specialist technology, data access, and ongoing costs for your chosen scope.
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.