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.
The HP 48 is the calculator of a generation of engineers, physicists and students: the 48SX of 1990 brought RPN, RPL programming, units, symbolic algebra and graphing into one machine, the 48GX of 1993 added the equat...
$5.99
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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.
Your first Build Kit is free with a verified email.
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.
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Original App Store material. Ratings and screenshots describe the existing app, not proof of demand for your version.
The HP 48 is the calculator of a generation of engineers, physicists and students: the 48SX of 1990 brought RPN, RPL programming, units, symbolic algebra and graphing into one machine, the 48GX of 1993 added the equation library, the solver applications, more memory and a faster processor. Thirty years on, many still keep one on their desk — and this app puts one in your pocket. RPN 48 is not an imitation: it emulates the calculator's hardware — the Saturn processor, the memory controllers, the 131×64 display, the keyboard, the timers — and runs HP's original ROM, so it behaves exactly as the real machine: every function, every menu, every flag, every quirk. THE CALCULATOR • RPN with the four-level stack (and unlimited stack depth), or algebraic entry, at your choice • Symbolic algebra: expressions, simplification, derivatives, integrals, Taylor series, equation solving; exact rational and integer arithmetic • Scientific calculator: complex numbers, vectors and matrices, statistics and regressions, unit conversions with dimensional analysis, base conversions (BIN/OCT/HEX), numeric solver, financial (TVM) calculations, dates and times • Graphing: function, polar, parametric, conic, differential equation, statistics and 3D plots, with zoom and trace • The 48G series' Equation Library with 300 equations of physics and engineering, with units • Programmable in RPL: your programs run as on the real machine THE APP • Both models: the HP 48GX (ROM revisions R and P, the 48G series' 128 KB) and the HP 48SX (ROM revisions J and E), each at its own speed and with its own memory • Your calculator's memory stays: close the app, come back later, it is exactly where you left it • HP's manuals (Quick Start Guide, User's Guide, Advanced User's Reference) can be downloaded into the app and read next to the calculator; the app remembers your page • Hardware keyboard support on iPad and iPhone • Works fully offline, no account, no ads, no tracking ABOUT THE ROM The app contains no HP software. On first launch you pick a model and its ROM image is downloaded from hpcalc.org, the community archive where HP allowed the HP 48 ROMs to be published in 2000, exactly as you would with a browser; the image is then kept on your device. HP, HP 48, HP 48SX and HP 48GX are trademarks of HP Inc. This app is an independent project and is not affiliated with or endorsed by HP.
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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.
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.
Not assessed in a Build Kit yet.
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.