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
Vicinno Financial Calculator
The most reliable emulator for HP 12C Financial Calculator on iPhone and iPad, which behaves exactly like, and supports all the functions of HP 12C Financial Calculator.
$5.99 · In-app purchases
PRICE
$5.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.2
1,209 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.
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
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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 included17 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 Vicinno Financial 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
Implement a modern UI with a user-friendly design.
Assumption to check: Users find the app's interface outdated and not user-friendly.
Validate with people who use this workflow before building.
Hypothesis 2
Add more financial calculations and types.
Assumption to check: Limited calculation types available.
Validate with people who use this workflow before building.
Hypothesis 3
Create a more subtle and user-friendly monetization strategy.
Assumption to check: In-app purchase prompts can be intrusive.
Validate with people who use this workflow before building.
Hypothesis 4
Include an onboarding tutorial and help sections for users.
Assumption to check: Lack of tutorial or help sections.
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
The most reliable emulator for HP 12C Financial Calculator on iPhone and iPad, which behaves exactly like, and supports all the functions of HP 12C Financial Calculator. 5 Stars: "Works like the original but more handy" -Jen, CFA, MBA, Financial Analyst 5 Stars: "Best 12c out there. Nice to always have it with me." -Tim H. Nelson, Finance student 5 Stars: "Turns your iPhone into a 12c with helpful features, not in the original" -Hannah 5 Stars: "Retired my very experience HP several years ago and haven't looked back. Only use this app now." -Yan07 5 Stars: "I use it on a daily basis and no longer have to carry my financial calculator with me." -Debbie, Financial Advisor 5 Stars: "couldn't be a better app. Stable user-friendly and the exact replacement for my physical Hewlett Packard calculator." -Gatortag This app uses the same RPN (Reverse Polish Notation) entry system and adds in big improvements for mobile to guarantee the best user experience and performance. ******** Highlight Features ******** • Time value of money TVM • Cash flow analysis NPV, IRR • Amortization • Bonds • Depreciation • Loan payments calculation • Statistical analysis • Date arithmetic • RPN entry • Programmable • Support auto-rotate and can be used in both orientations: landscape and portrait. • In-app quick start help with one click access. • Options to turn on/off audible key click feedback, and • Switch between the US and Europe number format/use comma as decimal point. • Automatically save/restore all settings. • In-app online support. • Click menu key to see more settings. • Long press to copy the calculation result to the clipboard and paste it anywhere. • More ... **** Support **** Feel free to email us at [email protected]. **** Stay tuned **** Like us: www.facebook.com/vicinno Follow us: www.twitter.com/vicinno
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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.
SUGGESTED BUILD STACK
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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.
