App Overview

Calc-12E RPN Financial icon

Calc-12E RPN Financial

Stone Meadow Development LLC · Business

5 Stars

$1.99 · In-app purchases

PRICE
$1.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
4.0
20 ratings · Top 30%

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 included18 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.

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.

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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> SELECT BUILD PLATFORM:

Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.

// RORK SYSTEM PROMPT
Rork plan preview for Calc-12E RPN Financial: map the core Business 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 more financial functions like investment calculations.

Assumption to check: Limited advanced functions compared to competitors

Validate with people who use this workflow before building.

Hypothesis 2

Implement cloud storage for better user experience.

Assumption to check: No cloud sync for history

Validate with people who use this workflow before building.

Hypothesis 3

Redesign UI to be more modern and user-friendly.

Assumption to check: User interface feels outdated

Validate with people who use this workflow before building.

Hypothesis 4

Add a guided tutorial for new users.

Assumption to check: No tutorial or help section

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

5 Stars. “I can't tell you how often I use it, probably about as much as the phone app!" - CharlieW, President. Waterman & Company (Real Estate Investment and Development) “This is the first 12C type calculator for the itouch that has actually made me put down my real 12C. One of the best features of this calculator is the register display where you can see what is in FV, I, PV, PMT, etc. That alone makes it worth the $14.95 price. Consider the many other features that it has over and above the real 12C and you have one sweet program here. Best of the 12C emulators out there - hands down! “ - tsinvest It started in early 2008 with a belief that: • there was one and only one insanely great financial calculator • the iPhone is the perfect platform to bring that calculator back to life • it's not good enough to just copy the old, you have to make it better • a financial calculator is a professional tool, not a game From this mindset came Calc-12E, the first 12C emulator on the App Store. It was expensive back then ($20-$25) and compared to a game it still is because, well, you usually get what you pay for. Specifically: Foremost, if the math isn't right in the corner cases I can't trust the calculator. Calc-12E's algorithms were written for iOS by a (the?) key member of the original 12C development team who incorporated his solutions to the quirks in financial computation that historically tripped up lesser implementations. There are reasons the 12C was the absolute best, and Calc-12E draws directly on that heritage. While the original did what it could, 1980s technology made many features difficult, impractical or impossible to use. Calc-12E pioneered the following innovations to address shortcomings: • you can always see what's in the financial registers (and stack if you choose) so you have instant assurance that you've entered your data correctly. This feature has been copied by nearly every emulator on the App Store, for good reason. • visual cash flow editing radically eases how you deal with cash flows... believe it or not it is actually easy to manipulate cash flows with Calc-12E. There's a demo on YouTube, search for Calc12E. • Investment mode allows you to simultaneously evaluate metrics on up to three cash flow scenarios at a time. You can compare cash flows side-by-side AND because of visual cash flow editing you can play what-if games • the results of some calculations need to "leave the phone" to be useful. Amortization schedules, leasing terms, bond yields... everything can be sent via email using customizable templates Finally, a professional tool receives continuing support and updates. It does not nag you to rate it, it does not invite you to pay to get more. It does not crash. Check out Calc-12E's version history and reviews of previous versions. This is a live, supported app with tens of thousands of long term customers and I have never charged for an upgrade or cloaked features behind ads or paywalls. It's not ethical at this level (in my humble opinion!). When you buy Calc-12E you get my best (and evolving!) rendition of the most popular handheld calculator ever made. It's core (the math) comes from the same mind as your trusty original and to that foundation you get usability advances that actually enhance the overall tool.

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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
Advanced

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.