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
Calculator Keyboard - Faster
Calculator Keyboard - Faster
$2.99 · In-app purchases
PRICE
$2.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.4
9 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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Build Kit
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A product spec, screen plans, and build steps for your coding agent.
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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/
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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.
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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Quick prompt
Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.
// RORK SYSTEM PROMPT
Rork plan preview for Calculator Keyboard - Faster: map the core Productivity 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 advanced features like history, scientific calculations, or memory functions.
Assumption to check: Limited functionality compared to full calculator apps
Validate with people who use this workflow before building.
Hypothesis 2
Implement a more organized layout with customizable options.
Assumption to check: User interface can be cluttered
Validate with people who use this workflow before building.
Hypothesis 3
Optimize performance for smoother interactions.
Assumption to check: Occasional performance lags on older devices
Validate with people who use this workflow before building.
Hypothesis 4
Ensure all buttons have tactile feedback and consistent timing.
Assumption to check: Inconsistent button responsiveness
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
Calculator Keyboard - Faster Arithmetic, Advanced functions Use the "calculator keyboard" to retain the calculation process and quickly calculate the results. No need to switch between applications, no need to copy and paste, calculate anytime, anywhere, convenient and fast. [Small] Less than 10 trillion [Quick] Quick start, fast input, fast calculation [Strong] Four operations, advanced functions Arithmetic: 1-2 + 3 × 4 ÷ 5 = 1.4 Parentheses: 10 ÷ (1 + 2) = 3.3333 More: π-5% + e + 10 ^ 2 + sin (90 °) + ∛9 + ln (3) + 5! = 229.8815 1/5 + cos (45 °) = 0.9071 10 ÷ 4 = 2.5 Supported operations and functions: - Arithmetic - Brackets - Pi π, percentage%, golden ratio ϕ, natural constant e - Square x², cubic x³, y power x ^ y - Square root √, cubic root ∛ - Trigonometric functions sin, cos, tan - Inverse trigonometric functions asin, acos, atan - Hyperbolic functions sinh, cosh, tanh - Natural logarithm ln, constant logarithm log - Random number rand - e to the power of x e ^ x - Countdown 1 / x - Power of 10 x 10 ^ x other: - Custom slide up input - Custom toolbar - History record - Button sound effects - Key vibration - Cursor movement - Angles and radians - Implicit multiplication - Retain decimal places - Keep results only - Long press to delete continuously - Quick input by sliding up - Automatically complete brackets - Dark mode contact: If you have a feature you want, or other suggestions or comments, please leave a comment or email us. If you find it useful, I look forward to you taking a minute to rate it and write two comments, useful comments and five stars will make it a bit ahead of the list, thanks! Email: [email protected]
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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
React Native
Expo
React Navigation
TypeScript
Redux
Axios
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.
