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
HP 12C Platinum Calculator
Meet the next generation of your favorite calculator
$16.99 · In-app purchases
PRICE
$16.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 1.6
351 ratings · Below Average
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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Build Kit
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A product spec, screen plans, and build steps for your coding agent.
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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 HP 12C Platinum Calculator: 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
Add features like graphing or financial modeling.
Assumption to check: Limited functionality compared to physical calculators.
Validate with people who use this workflow before building.
Hypothesis 2
Implement a modern, clean UI design.
Assumption to check: User interface feels outdated and cluttered.
Validate with people who use this workflow before building.
Hypothesis 3
Optimize for performance and resource usage.
Assumption to check: Poor performance on older devices.
Validate with people who use this workflow before building.
Hypothesis 4
Introduce a freemium model with essential features for free.
Assumption to check: High price point compared to free alternatives.
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
Meet the next generation of your favorite calculator. The official HP 12c Platinum app, now brings a completely redesigned interface, a modern look, and improved functionality—while preserving the precision and reliability trusted by professionals for decades. Built for everyday use in business, banking, real estate, and education, the new HP 12c Platinum brings a timeless classic into the modern era. The HP 12c Platinum You Know – Now Better Than Ever • Official emulator of legendary calculator device by Hewlett-Packard • Identical algorithms, layout, and keystrokes as the original HP 12c Platinum • RPN (Reverse Polish Notation) for fast and efficient input • Built-in financial tools: loan payments, TVM, NPV, IRR, cash flows, bonds, and more Be Ready. Anywhere. Anytime. Whether you’re in class, at the office, or on the go, HP 12c Platinum is ready when you are. Just launch the app on your iPhone and get to work. Download HP 12c Platinum today and experience the perfect blend of classic functionality and modern design.
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
React Native Gesture Handler
React Native Reanimated
TypeScript
BUILD KIT DIFFICULTY
Intermediate
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.
