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
10bII Financial Calculator PRO
10bII Calculator has a formidable reputation of being the best financial calculator app
$5.99 · In-app purchases
PRICE
$5.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.6
247 ratings · Top 15%
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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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 10bII Financial Calculator PRO: 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 more advanced financial functions like amortization schedules or investment analysis.
Assumption to check: Limited features compared to desktop counterparts
Validate with people who use this workflow before building.
Hypothesis 2
Simplify the UI and offer a tutorial for first-time users.
Assumption to check: Complex user interface for beginners
Validate with people who use this workflow before building.
Hypothesis 3
Introduce themes and layout adjustments to enhance user experience.
Assumption to check: Lack of customization options
Validate with people who use this workflow before building.
Hypothesis 4
Optimize the app for better performance across all device types.
Assumption to check: Inconsistent performance on older devices
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
10bII Calculator has a formidable reputation of being the best financial calculator app. It is suitable for all types of users, whether they are looking to carry out basic car loans or advanced Cash-Flow calculation; This Financial Calculator has the answers to EVERY FINANCIAL QUESTIONS! It is equipped with a powerful FINANCIAL CORE advocated by powerful USE CASES support, which increases its functionality by leaps and bounds, making it an ideal choice for sales assistant & bankers, financial students etc... It comes with an in depth Tutorial Video to answer any questions you have, regarding the app and to help you further understand the world of advanced finance. ◉ ADVANCED FEATURES: ▸ Scientific Functions (MathDisp. Mode) ▸ Time-Value-Money Solving ▸ Amortization Schedule ▸ 2 Variables Statistics ▸ Linear Regression ▸ Uneven Cash-Flow Calculation ▸ Margin & Markup Calculation ▸ Advanced MATH Display Mode ▸ Functions History Bar ▸ 10 Extended Memory Slots ▸ Copy/Paste & Sharing ▸ 2 Flat Morden Themes & Legacy one. ◉ GRAPH & DIAGRAM: ▸ Scatter Plot ▸ Linear Regression ▸ Cash Flow Diagram. ◉ USE CASES: ▸ Save & Load Multiple Data ▸ Basic Financial Use Cases ▸ Date Calculation ▸ Loans, Bill Split, Tips, ▸ And More... ◉ CURRENCIES/UNIT CONVERTER: ▸ 80+ Popular Currencies Update Hourly. ▸ 1000+ Units in 50 Categories ◉ TUTORIAL VIDEO: ▸ Basic Calculation Video ▸ Work with Use Case & Sharing Data. IT IS THE BEST FINANCIAL CALCULATOR !!!!!!! We love your feedback, Thanks a lot ! Please contact us for questions, bugs/crash reports, conversion requirements, etc…
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 Paper
Async Storage
Moment.js
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.
