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.
Calca is a powerful symbolic calculator that gives you instant answers as you type
$9.99 · In-app purchases
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.
A product spec, screen plans, and build steps for your coding agent.
First kit free with a verified email
Combine features and design from your favorite apps.
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Generating… usually about a minute.
What should your app do differently? Your note travels with the kit so your coding agent builds around your idea.
A product spec, phased build plan, differentiation notes, and screen references.
Illustrative example: an invoice app for independent contractors. Your kit is tailored to the app you choose; this is not its generated content.
Goal: Send a clear invoice after finishing a job.
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.
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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Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.
Rork plan preview for Calca: 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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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
Assumption to check: Limited functionality for mathematical functions
Validate with people who use this workflow before building.
Hypothesis 2
Assumption to check: Difficult to organize notes effectively
Validate with people who use this workflow before building.
Hypothesis 3
Assumption to check: Lack of cloud sync options
Validate with people who use this workflow before building.
Original App Store material. Ratings and screenshots describe the existing app, not proof of demand for your version.
Calca is a powerful symbolic calculator that gives you instant answers as you type. It solves equations and simplifies complex expressions - it's a computer algebra system in your pocket! It's also a rich Markdown text editor so that you can explain your ideas alongside your calculations. Calca is perfect for professionals and students - anyone who works with numbers and equations. Variables and functions can be created with only a few keystrokes and can be manipulated with a rich library of operators and functions. Calca updates as you type - just like a spreadsheet. You can declare variables, edit their values and watch everything update before your eyes. Since everything is calculated on the device - no network needed - you get answers instantaneously. All calculations are stored as plain text so you can easily share them with other editors and move them from device to device. Calca has been designed to work with iCloud documents so all your devices can access your calculations - you'll always have the latest files ready for viewing and editing. Calca comes with a suite of examples to help you get started covering topics from home mortgages to kinetics. All these examples are fully explained within Calca itself. Are you still using a desktop calculator? Are you using the calculator with the giant buttons that came with your OS? Computers are much more capable than doing simple one-line arithmetic - put your machine to work with Calca! Calculation Features: • Variables `x = 42` • Functions `f(c) = 9/5*c + 32` and even recursive functions • Units `42 mph in kmph` and currency `¥599 in $` • Solves equations (`x + 2x + 4x = 42`, what is x?) • Matrices with inverses so you can solve linear equations • Sum, prod, map, and reduce operations on lists, matrices, and ranges • Trigonometry and complex numbers • Derivatives of functions • Logic operations and if statements • Binary math (& and |) and support for binary and hex number (`0xA9` and `0b1010`) • Keeps track of units (m, s, m/s, m/s^2, etc.) so you can verify your equations as you compute Please visit http://calca.io to see lots of examples. Thank you for looking!
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Plan a focused first version with your coding agent. These are planning assumptions, not a delivery guarantee.
Choose one audience and one core workflow. Use the kit to agree on its screens, data, and acceptance criteria before building.
Decide which secondary features, integrations, and platform support can wait. Your version does not need to reproduce everything in the original.
Validate external services, specialist technology, data access, and ongoing costs for your chosen scope.
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.